1.introduction complete

7/31/2019 1.Introduction Complete

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1.1 PHYTOCHEMICALS:

1.1.1 DEFINITION AND CHEMISTRY:

Phyto is the latin word for plant so basically phytochemical would be anything that

comes from a plant. Phytochemicals are non-nutritive plant chemicals that have protective or

disease preventive properties. There are more than thousand known phytochemicals. It is well-

known that plant produces these chemicals to protect itself but recent research demonstrates that

they can protect humans against diseases. Some of the well-known phytochemicals are lycopene

in tomatoes, Isoflavones in soy and Flavonoids in fruits. They are not essential nutrients and are

not required by the human body for sustaining life.

Figure 1: A plant of Boroccli

Phytochemicals are chemicals found in plants. Plant sterols, flavonoids (FLAV'oh-

noidz), and sulfur-containing compounds are three classes of micronutrients

Truba Institute of Pharmacy, Bhopal 1


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found in fruits and vegetables. These compounds may be important in reducing

the risk of atherosclerosis (ath"er-o-skleh-RO'sis), which is the buildup of fatty

deposits in artery walls. Within these categories are many possible compounds,

most of which aren't well described and whose modes of action aren't

established. Many other plant products may also be linked to the atherosclerotic

process, such as antioxidant vitamins, phytoestrogens and trace minerals.

These plant micronutrients will clearly be the topic of future research. As work

continues on all these compounds, other unrecognized components in plants will

be identified that may have promise in reducing risk of cardiova scular disease.

[1,2,3,4]

1.1.2 BIOLOGICAL BACKGROUND:

All plants produce chemical compounds as part of their normal metabolic activities.

These include primary metabolites, such as sugars and fats, found in all plants, and

secondary metabolites found in a smaller range of plants, some useful ones found

only in a particular genus or species. Pigments harvest light, protect the organism

from radiation and display colors to attract pollinators. Many common weeds have

medicinal properties.

The functions of secondary metabolites are varied. For example, some secondary

metabolites are toxins used to deter predation, and others are pheromones used to

attract insects for pollination. Phytoalexins protect against bacterial and fungal

attacks. Allelochemicals inhibit rival plants that are competing for soil and light.

Plants upregulate and downregulate their biochemical paths in response to the local mix

of herbivores, pollinators and microorganismsThe chemical profile of a single plant

may vary over time as it reacts to changing conditions. It is the secondary

metabolites and pigments that can have therapeutic actions in humans and which can

be refined to produce drugs. [1,2,3,4]

1.1.3 TYPE OF PHYTOCHEMICALS:

Plants synthesize a bewildering variety of phytochemicals but most are derivatives of a

few biochemical motifs.



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Alkaloids contain a ring with nitrogen. Many alkaloids have dramatic effects on the central

nervous system. Caffeine is an alkaloid that provides a mild lift but the alkaloids in

datura cause severe intoxication and even death.

Phenolics contain phenol rings. The anthocyanins that give grapes their purple color, the

isoflavones, the phytoestrogens from soy and the tannins that give tea its astringency

are phenolics.

Terpenoids are built up from terpene building blocks. Each terpene consists of two paired

isoprenes. The names monoterpenes, sesquiterpenes, diterpenes and triterpenes are

based on the number of isoprene units. The fragrance of rose and lavender is due to

monoterpenes. The carotenoids produce the reds, yellows and oranges of pumpkin,

corn and tomatoes.

Glycosides consist of a glucose moiety attached to an aglycone. The aglycone is a molecule

that is bioactive in its free form but inert until the glycoside bond is broken by water

or enzymes. This mechanism allows the plant to defer the availability of the

molecule to an appropriate time, similar to a safety lock on a gun. An example is the

cyanoglycosides in cherry pits that release toxins only when bitten by a herbivore.

The word drug itself comes from the Dutch word "droge" (via the French word Drogue),

which means 'dried plant'. Some examples are inulin from the roots of dahlias,

quinine from the cinchona, morphine and codeine from the poppy, and digoxin from

the foxglove.

The active ingredient in willow bark, once prescribed by Hippocrates, is salicin, which is

converted in the body into salicylic acid. The discovery of salicylic acid would

eventually lead to the development of the acetylated form acetylsalicylic acid, also

known as "aspirin", when it was isolated from a plant known as meadowsweet. The

word aspirin comes from an abbreviation of meadowsweet's Latin genus Spiraea,

with an additional "A" at the beginning to acknowledge acetylation, and "in" was

added at the end for easier pronunciation. "Aspirin" was originally a brand name,

and is still a protected trademark in some countries. This medication was patented by

Bayer AG.

[1,2,3,4]



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Figure 2: Some phytochemicals with their structure.



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Table No.1: Some phytochemical with their main constituents. [1-5]



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1.2. SCREENING

1.2.1 DEFINITION:

Screening is the process of separation and isolation of active principle from plant sources.

1.2.2 SCREENING IS HELPFUL:

To get lead for Discovery of new therapeutic agents.

To find New sources for economic material.

To help expand Chemotaxonomy.

To produce Semi synthetic derivatives.

1.2.3 STEPS:

For this purpose, following 3 essential steps are prescribed:

Selection of plant.

Phytochemicals screening.

Phytopharmacological evaluation. [3,5]

1.3 PHYTOCHEMICAL SCREENING:

1.3.1 DEFINITION:

It is a process of tracing plant constituents. For example you want to found out if a certain

plant contains alkaloids (a plant constituent) then, you will be performing a

phytochemical screening procedures for alkaloids (in this case Mayers and

Wagners test). There are general plant constituents that can be performed with a

standard test. And these are screening for:

Alkaloids

Saponin glycosides

Cardenolides and Bufadionolides

Flavanoids

Tannins and Polyphenolic compunds



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Anthraquinones

Cyanogenic glycosides

Carbohydrates

Fixed oils, Fats, and Volatile oils.[1- 6]

1.3.2 PHYTOCHEMICAL SCREENING APPROACHES:

The ultimate goal in surveying plants for biologically active or rnedicinally useful

compounds should be to isolate the one or more constituents responsible for a particular

activity. Hence with the selection of a specific plant for phytochemical investigation either on

the basis of one or more approaches set forth under phytopharmacologic Approaches, or

through some other avenue, phytochemical screening techniques can be a valuable aid.

Certain investigators feel that an initial selection of investigational plants should be made not

on evidence that extracts elicit a particular and interesting biological activity, but rather on the

basis that certain chemicals are present in the plant, relatives of which can usually be associated

with biological activity. Thus, some investigators will select initially only alkaloid-containing

plants for study on the premises that:

Normally exert some type of pharmacologic activity usually on the center nerves systems but

not always so;

The greatest majority of natural products used in medicine today are alkaloidal in nature;

Tests for the presence of these compounds in plants are simple, can be conducted rapidly, and

are reasoanably reliable, and

Because of their chemical nature, alkaloids are more easily manipulated making extraction

and isolation less of a problem.

In addition, economics , as well as other factor associated with biological testing, often force

the investigation to pursue a phytochemical group other then alkaloids be selected for

investigation say the flavonols , the diversity of expected biological activities can be enormous.

Willaman has surveyed the literature and has found that at least natural flavonoids are known,

occurring in some families, genera, and species of plants . Also, some different pharmacologic or

biological activities have been reported for one or more of flavonoids . More recently,



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horhammer and wagner have reviewed the same area, and these numbers are therefore to be

increased . Also, orzechowski has considered the role of flavonids as therapeutic agent. Along

similar lines, the coumarins have been repoterd to exert some 31 different biological effert , and

according to soine , their full range of farmacologic activities is not apprericiated by most

investigators. Other examples pointing out the complexity of expected biological effects for any

one category of phytoconstituents could of course be made.In any event publication representing

the phytochemical screening approach for out wigh those following phytopharmacologic avenues

not only numbers of report but in representation of total plant examined.

Since the number of chemical categories of plant constitutes is great and each is capable of

eliciting biological activity no attempt will be made in this to be all enclusive. This section of the

review will be restricted to some consideration of phytochemical screening methodology

followed by discussions of those categories of phytoconstituents.

Which have been represented in major published surveys of screening programs. These will

include: alkaloids, Glycosides as a general class (heteroside) sapgrams. (Steroids and

triterpenoid) sterols, Cardiac glycosides, Cyanogenetic glycosides, Isothiocyanate glycosides.

cyanogenetic glycosdes, isothiocyanate glycosides, anthraquinones, flavonoids and related

compounds. Surveys which have decn condussed along with the general metehodology involved.

The examples to be coted are intended to be representative of each class and are not recant to

include all available published data. [2-6, 8-11]

1.3.3 GENERAL CONSIDERATION:

A method for use in phytochemical screening should be :

Simple,

Rapid,

Designed for a minimum of equipment

Reasonably selective for the class of compounds under study

Quantitative in so far as having a knowledge of the lower limit of detection is concered, and

if possible

Should give additional information as to the presence or absence of specific members of the

group being evaluated. Most published procedures adhere to criteria.



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In fact, certain procedure cannot be duplicated because of insufficient details included in

some report. For example,Arthur and cheung in a phytochemical survey of Hong kong plants,

screened 332 species for alkaloids. They equated the precipitates observed following the

additional of standard alkaloid precipitating reagents to result obtained by addition the same

reagents to standard solution of 1:100, 1:500, 1:2500, and 1;10,000quinine sulfate. It is implied

that water was the solvent. However , the solubility of quinine sulfate is stated to be 1gm.in 810

ml. of water. Along similar lines, will have used the cyanidin test for the detection of the alfa-

benzofurane nucleus as indicative of the presence of flavanoids. They compare a test result color

with a similar color produced by a 0.1% solution of rutin and equate it as a (+) reaction. Their

extraction solvent is 95% ethanol (but fresh plant inaterial was often extracted which would

decrease this percentage considerably), and rutin is stated to be only slightly soluble in ethanol

and soluble about l Gm. in 8 L. of water. We find that maximum solubility of rutin at room

temperature is about 0.02% for both 80 and 95% ethanol.

Webb, using a field method, estimated alkaloid precipitates with reagents on a + to ++++

basis but used no reference for comparison . IIe also states, on the other hand, while the method

may yield a percentage of false positives; it has never failed to detect species with alkaloids .

If the initial field test did indeed fail to detect alkaloids, perhaps because of a lowconcentration in the plant, how could it be determined that the test was infallible when only

field test positives species were colleted for more specific laboratory examination . [11-14]

1.3.4 FUNDAMENTAL CONSIDERATION:

One of the most important and fundamental consideration in designing a phytochemical

screening produce is the selection of proper extraction solvent. It is often difficult to follow

general or expected solubility rule for a given class of phytoconsitutents since there are often

substance of unknown character present in crude plant extracts that affect solubility. For

example, woo has reported that effect of saponin in plant extracts on the solubility of certain

normally insoluble compounds using selected solvent. Apparently saponin acts as a wetting

agent to enhance the formation of micelles; thus an increase in solubility of certain constituents is

effected. This phenomena has been noted through the use of synthetic detergents to enhance the

solubility, and thus extract ability of alkaloids from cinchona . Since saponins, or other similarsurface-active agents, do not occur universally in plants, prediction of general solubilities for a



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class of phytoconstituents ppt. a major problem. In our laboratory n-hexane-soluble extractives

from catharanthus lanceus were found to be rich in alkaloids. Subsequent isolation of individual

alkaloids from the crude mixture proved them to be totally insoluble in n-hexane. Presumably the

alkaloids occur in the plant, at least in this instance dissolved in some lipid material, the latter

being soluble in n-hexane.

No solution is offered for these problemes involving solubility except tosay that extract

residues should always be examined with a variety of solvents to determine whether solubility

phenomena have occurred. [11-15]

1.4 PHYTOCHEMICAL SCREENING TECHNIQUES:

Techniques used in phytochemical screening are:

1.4.1 EXTRACTION:

The process of obtaining something from a mixture or compound by chemical or physical

or mechanical means is called extraction. Extraction refers to the extraction of aromatic

compounds from raw materials, using methods such as distillation, solvent extraction,

expression, or enfleurage. The results of the extracts are either essential oils, absolutes,

concretes, or butters, depending on the amount of waxes in the extracted product. [16,17]

1.4.1.1 Spouted Bed Extraction:

The mechanical extraction of the bixin from Bixa orellana seeds using a spouted bed was

investigated in this work. The experimental program was divided into two main

steps. In the first step, a two-level factorial experimental design was used to analyzethe influence of the main process variables on the mechanical extraction responses.

The second step of the experiment was carried out to evaluate the effect of the

distance between the draft tube and the conical base (ht). Computational fluid

dynamic technique was used to understand seed flow and the effect of h t on the

mechanical extraction process. The results obtained showed that the presence of the

draft tube was the variable that most strongly affected the powder extraction. The

best condition for the bixin extraction from B. orellana seeds was the one when thedraft tube was positioned at 4 cm from the air inlet.[17]



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Figure 3: Bixa orellana seeds

1.4.1.2 Super Critical Fluid Extraction:

A supercritical fluid is any substance at a temperature and pressure above its critical point.

It can diffuse through solids like a gas, and dissolve materials like a liquid.

Additionally, close to the critical point, small changes in pressure or temperature

result in large changes in density, allowing many properties to be "tuned".

Supercritical fluids are suitable as a substitute for organic solvents in a range of

industrial and laboratory processes. Carbon dioxide and water are the most



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commonly used supercritical fluids, being used for decaffeination and power

generation respectively

Unlike more traditional methods of extraction SFE uses no additional solvents in the

process, which translates to substantial cost savings due to a reduction in post-

processing steps, clean-up, and safety and assurance measurements. More

importantly the resulting natural extraction is of the purest quality possible with no

residual contamination from other chemicals.[18,19,20,21]

Figure 5: Super critical fluid extraction

1.4.1.3 Solid Phase Micro-Extraction, OR SPME:

SPME can be thought of as a very short gas chromatography column turned inside out.

SPME involves the use of a fibre coated with an extracting phase, that can be a

liquid (polymer) or a solid (sorbent), which extracts different kinds of analytes

(including both volatile and non-volatile) from different kinds of media, that can be

in liquid or gas phase. The quantity of analyte extracted by the fibre is proportional

to its concentration in the sample so long as equilibrium is reached or, in case of

short time pre-equilibrium, with help of convection or agitation. [22-27]



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Figure 6: Solid-Phase Micro extraction (SPME)[22]



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Figure 7: Solid-Phase Micro extraction (SPME) procedure [22]

1.4.2 SUBLIMATION:

Sublimation of an element or compound is a transition from the solid to gas phase with no

intermediate liquid stage. Sublimation is an endothermic phase transition that occurs

at temperatures and pressures below the triple point (see phase diagram). At normal

pressures, most chemical compounds and elements possess three different states at

different temperatures. In these cases the transition from the solid to the gaseous

state requires an intermediate liquid state. However, for some elements or substances

at some pressures the material may pass directly from a solid into the gaseous state.This can occur if the atmospheric pressure exerted on the substance is too low to

stop the molecules from escaping from the solid state.

Carbon dioxide is a common example of a chemical compound that sublimes at

atmospheric pressurea block of solid CO2 (dry ice) at room temperature and at

atmospheric pressure will turn into gas without becoming a liquid.[28,29,30,31]



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Figure 8: Sublimation apparatus

1.4.3 DISTILLATION:

Distillation is a method of separating mixtures based on differences in their volatilities in a

boiling liquid mixture. Distillation is a unit operation, or a physical separation

process, and not a chemical reaction.[32-36]

1.4.3.1 Simple distillation:

In simple distillation, all the hot vapors produced are immediately channeled into a

condenser which cools and condenses the vapors. [32-36,]



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. Figure 9: Simple distillation

1.4.3.2 Fractional distillation:

For many cases, the boiling points of the components in the mixture will be sufficiently

close that Raoult's law must be taken into consideration. [32-42]



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Figure 10: Fractional distillation

1.4.3.3 Steam distillation:



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Like vacuum distillation, steam distillation is a method for distilling compounds

which are heat-sensitive. This process involves using bubbling steam through a

heated mixture of the raw material. [31-45]

Figure 11: Steam distillation apparatus

1.4.3.4 Vacuum distillation:



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Some compounds have very high boiling points. To boil such compounds, it is often

better to lower the pressure at which such compounds are boiled instead of

increasing the temperature. Once the pressure is lowered to the vapor pressure of the

compound (at the given temperature), boiling and the rest of the distillation process

can commence. This technique is referred to as vacuum distillation and it is

commonly found in the laboratory in the form of the rotary evaporator.

This technique is also very useful for compounds which boil beyond their

decomposition temperature at atmospheric pressure and which would therefore be

decomposed by any attempt to boil them under atmospheric pressure.

[32,33,34,35,36,37,38,39,40,41,42,43,44,45,46]

Figure 12: Vacuum distillation apparatus

1.4.3.5Air-sensitive vacuum distillation:



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Some compounds have high boiling points as well as being air sensitive. A simple vacuum

distillation system as exemplified above can be used, whereby the vacuum is

replaced with an inert gas after the distillation is complete. [32,34,35,36,37,38,39]

1.4.3.6 Short path distillation:

Short path vacuum distillation apparatus with vertical condenser (cold finger), to minimize

the distillation path; 1: Still pot with stirrer bar/anti-bumping granules 2: Cold finger

- bent to direct condensate 3: Cooling water out 4: cooling water in 5: Vacuum/gas



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inlet 6: Distillate flask/Distillate.[37,38,39,40]

Figure 13: Short path distillation apparatus



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1.4.3.7 Azeotropic distillation:

Interactions between the components of the solution create properties unique to the

solution, as most processes entail nonideal mixtures, where Raoult's law does not

hold. Such interactions can result in a constant-boiling azeotrope which behaves as if

it were a pure compound (i.e., boils at a single temperature instead of a range). At an

azeotrope, the solution contains the given component in the same proportion as the

vapor, so that evaporation does not change the purity, and distillation does not effect

separation. For example, ethyl alcohol and water form an azeotrope of 95.6% at 78.1

C. [45-55]

Figure 14: Azeotropic distillation apparatus



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1.4.4 CHROMATOGRAPHY:

It is the collective term for a family of laboratory techniques for the separation of

mixtures. It involves passing a mixture dissolved in a "mobile phase" through a

stationary phase, which separates the analyte to be measured from other molecules in

the mixture and allows it to be isolated. [56-60]

1.4.4.1 Column chromatography:

Column chromatography is a separation technique in which the stationary bed is within

a tube. The particles of the solid stationary phase or the support coated with a liquid

stationary phase may fill the whole inside volume of the tube (packed column) or be

concentrated on or along the inside tube wall leaving an open, unrestricted path for

the mobile phase in the middle part of the tube (open tubular column). Differences in

rates of movement through the medium are calculated to different retention times of

the sample.[56-62]



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Figure 15: Manual and Automated ion column chromatography

1.4.4.2 Planar Chromatography:

Planar chromatography is a separation technique in which the stationary phase is

present as or on a plane. The plane can be a paper, serving as such or impregnated by

a substance as the stationary bed (paper chromatography) or a layer of solid particles

spread on a support such as a glass plate (thin layer chromatography). Different

compounds in the sample mixture travel different distances according to how

strongly they interact with the stationary phase as compared to the mobile phase.

The specific Retardation factor (Rf) of each chemical can be used to aid in the

identification of an unknown substance. [57-64]

1.4.4.3 Paper Chromatography:

Paper chromatography is a technique that involves placing a small dot or line of sample

solution onto a strip of chromatography paper. The paper is placed in a jar

containing a shallow layer of solvent and sealed. As the solvent rises through the

paper, it meets the sample mixture which starts to travel up the paper with the

solvent. This paper is made of cellulose, a polar substance, and the compounds

within the mixture travel farther if they are non-polar. More polar substances bond

with the cellulose paper more quickly, and therefore do not travel as far.[57-64]



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. Figure 16: Paper Chromatography

1.4.4.4 Thin layer chromatography:

Thin layer chromatography (TLC) is a widely-employed laboratory technique and is

similar to paper chromatography. However, instead of using a stationary phase of

paper, it involves a stationary phase of a thin layer of adsorbent like silica gel,

alumina, or cellulose on a flat, inert substrate. Compared to paper, it has the

advantage of faster runs, better separations, and the choice between different

adsorbents. For even better resolution and to allow for quantitation, high-

performance TLC can be used. [57-64]



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Figure 17: Separation of black ink on a TLC plate

1.4.4.5 Displacement Chromatography:

The basic principle of displacement chromatography is: A molecule with a high affinity

for the chromatography matrix will compete effectively for binding sites, and thus

displace all molecules with lesser affinities. There are distinct differences between

displacement and elution chromatography. In elution mode, substances typically

emerge from a column in narrow, Gaussian peaks. Wide separation of peaks,

preferably to baseline, is desired in order to achieve maximum purification. The



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speed at which any component of a mixture travels down the column in elution

mode depends on many factors. But for two substances to travel at different speeds,

and thereby be resolved, there must be substantial differences in some interaction

between the biomolecules and the chromatography matrix. Displacement

chromatography has advantages over elution chromatography in that components are

resolved into consecutive zones of pure substances rather than peaks. Because the

process takes advantage of the nonlinearity of the isotherms, a larger column feed

can be separated on a given column with the purified components recovered and the

figure of hplc shown .[63] .



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Figure 18: Displacement Chromatography

1.4.4.6 Gas chromatography:

Gas chromatography (GC), also sometimes known as Gas-Liquid chromatography,

(GLC), is a separation technique in which the mobile phase is a gas. Gas

chromatography is always carried out in a column, which is typically "packed" or

"capillary" (see below).[57-62]



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Figure 19: Gas chromatography1.4.4.7 High PerformanceLiquid chromatography:

Liquid chromatography (LC) is a separation technique in which the mobile phase is a

liquid. Liquid chromatography can be carried out either in a column or a plane.

Present day liquid chromatography that generally utilizes very small packing

particles and a relatively high pressure is referred to as high performance liquid

chromatography (HPLC). [58-64]



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Figure 20: High Performance Liquid chromatography

1.4.4.8 Affinity chromatography:

This is the most selective type of chromatography employed. It utilizes the specific

interaction between one kind of solute molecule and a second molecule that is

immobilized on a stationary phase. For example, the immobilized molecule may be

an antibody to some specific protein. When solute containing a mixture of proteins

are passed by this molecule, only the specific protein is reacted to this antibody,



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binding it to the stationary phase. This protein is later extracted by changing the

ionic strength or pH. [59-64]



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Figure 21: Affinity chromatography



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1.4.4.9 Supercritical fluid chromatography:

Supercritical fluid chromatography is a separation technique in which the mobile phase

is a fluid above and relatively close to its critical temperature and

pressure.Supercritical fluid chromatography is more versatile than high

performance liquid chromatography, more cost-efficient, user friendly, with higher

throughput, better resolution and faster analysis times than general liquid

chromatographic methods. The instrumentation that is required for supercritical fluid

chromatography is versatile because of its multi-detector compatibility.[56,57,59]

Figure 22: Supercritical fluid chromatography



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1.4.4.10 Ion exchange chromatography:

Ion exchange chromatography uses ion exchange mechanism to separate analytes. It is

usually performed in columns but can also be useful in planar mode. Ion exchange

chromatography uses a charged stationary phase to separate charged compounds

including amino acids, peptides, and proteins. In conventional methods the

stationary phase is an ion exchange resin that carries charged functional groups

which interact with oppositely charged groups of the compound to be retained. Ion

exchange chromatography is commonly used to purify proteins using HPLC.

[59-64]



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Figure 23: Ion Exchange chromatography

1.4.4.11Size exclusion chromatography:

Size exclusion chromatography (SEC) is also known as gel permeation chromatography

(GPC) or gel filtration chromatography and separates molecules according to their

size (or more accurately according to their hydrodynamic diameter or hydrodynamic

volume). Smaller molecules are able to enter the pores of the media and, therefore,

take longer to elute, whereas larger molecules are excluded from the pores and elute

faster. It is generally a low resolution chromatography technique and thus it is often

reserved for the final, "polishing" step of a purification. It is also useful fordetermining the tertiary structure and quaternary structure of purified proteins,

especially since it can be carried out under native solutioncondition. [59-64]



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Figure 24: Size exclusion chromatography

1.4.4.12 Countercurrent chromatography:

Countercurrent chromatography (CCC) is a type of liquid-liquid chromatography,

where both the stationary and mobile phases are liquids. It involves mixing a

solution of liquids, allowing them to settle into layers and then separating the layers.

[59-64]



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Figure 25: High-speed counter-current chromatography

1.4.4.13 Adsorption Chromatography:

Adsorption chromatography is probably one of the oldest types of chromatography around. It

utilizes a mobile liquid or gaseous phase that is adsorbed onto the surface of a



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stationary solid phase. The equilibriation between the mobile and stationary phase

accounts for the separation of different so.[57-64]

Figure 26: Adsorption Chromatography

1.4.5 ALKALOID SCREENING:

Prior to a consideration of screening plant material for alkaloids. It would seem in order

to define the term alkaloids as used in this review; however the nature of the word. It self



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precludes any thing more then a vague definition. Any one familiar with alkaloids surely has

knowledge of their character but seldom can one give as acceptable definition. Most authorities

agree that chemical botanical and pharmacologic implications most be reflected an one

acceptable definition. Hegnauers suggestion that,

Alkaloids are more or less toxic substances which act primarily on the central nervous

system have a basic character contain heterocyclic nitrogen and are synthesized in plants from

amino acids or their immediate derivatives. In most eases they are of limited distribution in the

plant kingdom.

Seems as acceptable as any. For purposes of this discussion we will utilize Hegnauresconcept except. Of course, we cannot be concerned with the site of mechanism of synthesis , thus

compounds such as aliphatic nitrogenous bases amides and the amino acids themselves will not

be considered as alkaloids,

Estimates for the distribution of alkaloids in vascular plants have been placed as high as

15-20%, although this figure appears some what high with respect to data derived from several

extensive phytochemical screening programs Will have screened more then 4000 species of

plants and report a distribution of about 10% alkaloids. Webb in his experience with some 1700

species indicates alkaloids occurrence to be about 14% whereas the smith kline & French survey

found that about 10% of 25000 species screened were positive for alkaloids . since a few of these

undoubtedly will be determined through future studies to be false positive alkaloid containing

species, 9-10%seems to be the more logical estimate representing alkaloids yielding plant

species.

Alkaloids are widely distributed in the plant kingdom although certain groups have beenshown to be characteristically devoid of them excellent essays on this subject have been

published by willaman and Schubert and by Webb.[65-72]

1.4.5.1 Alkaloid detection:

Since alkaloids usually occur in plants as their water-soluble salts, some workers believethat extraction with acidulated water can result in a crude extract which can be tested directly



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with one or more standard alkaloid ppt. reagents. Other workers feel that the presence in such an

extract of materials that are capable of giving false-positive alkaloids test necessitate a

purification procedure before valid result can be obtained. This is usually accomplished by the

addition of base and subsequent extraction with water-immiscible organic solvent. The organic

extract can then de tested by application to filter paper, drying, and dipping or spraying with an

alkaloid detecting reagent that giver a chromo genic response with alkaloids. If the latter method

is not preferred, the organic solution can be re-extracted with dilute acid and the usual alkaloid

precipitating reagents added to separate portions of this acid extract.

Another method of removing impurities that are capable of giving false-positive tests

from an initial aqueous acidic extract is to salt out these materials by the addition of powdered

sodium chloride. An additional procedure for alkaloid detection could be based on the addition of

alkali directly to the powdered plant sample, followed by extraction with an appropriate organic

solvent. This extract could then be purified by partition as described above, or be tested directly.

With respect to these general methods, certain anomalies have been reported in the

literature which should be pointed out. There is no implication that these examples are frequently

encountered in alkaloid screening: however, one should be aware that they do exist. Certain

plants are known to contain labile non-basic constituents and may yield nitrogenous materials on

extraction with ammoniacal solvents, while others contain alkaloids that are susceptible to

modification by acidic reagents. That proteins, which may be present in aqueous or acidic

aqueous plants extracts, can ppt. on the addition of heavy metal alkaloid precipitating reagents

and thus yield false-positive tests, is well established. Such proteins can be removed by treatment

of the extract with sodium chloride prior to the use of the heavy metal reagent, a procedure which

usually salts out the protein. However, alkaloids such as alstonine may be quantitatively

precipitated as hydrochloride under these conditions. In the treatment of a crude plant extract to

remove impurities by the acid-base-organic solvent acid procedure, it is quite possible that plants

containing water-soluble alkaloid bases will go undetected. Quaternary bases, amine oxides,

betaines, and choline would full into this category.

Variability of results in alkaloid testing of plant material can, be induced by a number of

factors such as age, climate habitat plant part tested season time of harvest chemical races of

plants sensitivity of alkaloid type to reagents etc. A few examples regarding these factors shouldserve to point out their importance Geijera salicifolia was found by Webb to give consistently



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better alkaloid tests as the broad leaf form than narrow leaf form even when the 2 were growing

side by side in the field. In certain groups of plants (i.e. composite) alkaloids often arc found only

on or near the flower tops and in the Apocynaceae. Alkaloids generally tend to concentrate in the

root or bark often to the exclusion of other parts of the plant thus the proper selection of plant

parts for testing is quite important. To obtain equivalent results, quantitation of precipitates

obtained with alkaloid reagent is not always possible, especially when comparing different

genera or families. This is exemplified through knowledge that galbulimima baccata was found

to be rated a ++++ in field tests and subsequent analysis resulted in a yeald of 0.01%-0.05% of 4

alkaloids. A++++ rating for Daphnandra aromatica was determined in the field and subscquent

analysis in the laboratory yielded 6+% of crude alkaloids. Anlireha putaminosa loses 50% of its

alkaloid decomposition rates have also been noted for A. tennuifolia randia rubiaceous plants.

Silica gel drying of antirhea tennuifolia for 1 month resulted in material that gave a ++++

alkaloid test, whereas this same plant dried in the shade for 1month gave a negative alkaloid test.

Acronychina baueri on the other hand gave strong alkaloid positive tests when 124year old

herbarium specimens were evaluated Along similar lines , Raffauf and morris have reported that

a plant sample identified as Nicoliana attenuata and estimated to be some 1300 years old gave

positive alkaloid tests. Duboisia myoporoides yielded 3%of hyoscyaminne when harvested in

October but when harvested in April of the same year 3% hyoscine was isolated. Example of

alkaloid decomposition as a result of milling dried plant matcrial have also been cited. These

examples should suffice to point out just a few of the problems encountered by the natural

product investigator who is interested in the detection and isolation of biologically active

alkaloids. .[65-72]

1.4.5.2 SOME USEFUL ALKALOID PRECIPITATING REAGENTS:

NAME OF REAGENTS COMPOSITION



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Bouchardat Iodine-Potassium-Iodide

Dragendroff Bismuth potassium iodide

Ecolle Sillicotungstic acidHanger Picric acid

Kraut Iodine-zinc chloriodide

Marme Cadmium potassium iodide

Mayer Potassium mercuric iodide

Platinum chloride Chloroplatinic acid

Scheibler Phosphotungustic acid

Sonneschein Ammonium hosphomolybdateValser Potassium mercuric iodide

Wagner Iodinepotassiumiodide

Bismuth antimony iodide

Bromauric acid

Bromoplatinic acid

Bromothalic acid

Table No. 2: Some useful alkaloid precipitating reagents

1.4.5.3 Alkaloid detecting reagents:

For detecting alkaloids in phytochemical screening, two types of reagents are available,

alkaloidal precipitants and spray or dip reagents. In table-1 20 precipitating reagents commonly



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used for the detection of alkaloids, whereas in table-2 present 25 reagents that were used in 45

recent phytochemical surveys for alkaloids. At least 2 reagents were used in 38 of the surveys,

while 7 surveys depended solely on 1 reagent to establish the presence of alkaloids. Because of

the variable sensitivities of these reagents and because of their nonspecificity for alkaloids many

investigators utilize 4 or 5 reagents in their screening of plant extracts, and only samples yielding

precipitates with all reagents are considered to contain alkaloids. Fulton has tabulated some 200

of these reagents and presents a great deal of information concerning their specilicity and

sensitivity. A series of papers by munch a al is concerned with the effect of 17 different alkaloid

detecting reagents on several classes of nitrogenous bases. Travell has studied the sensitivity of

mayers and valsers reagents both solutions of potassium mercuric iodide and potassium iodide

and the letter from mercuric iodide and potassium iodide. [66-72]

The reagent used by most investigators for phytochemical screening is essentionally the

same formula that Mayer originally introduced in 1862. Several investigalors have demonstrated.

How ever. That the original formula is perhaps the least sensitive for alkaloid detection in

comparison with many proposed modifications. And travel has conclusively demonstrated the

superiority of several common alkaloid precipitating reagents using 40 different chemical types.

The reagents tested were mayers. Velsers wegners Bouchardats hagers Schreibers. Silicotangsticacid. Dregendorlls Marmes gold chloride.and sonnenscheins. It was demonstrated in this study

that the various reagents exhibit wide differences in sensitivity for structurally dissimilar

alkaloids. None of the reagents would detect ephedrine at a concentration of 0.1% but wagners

bouchardats. Dragendorffs and scheiblers each defected all of the other alkaloids at

concentrations ranging from 0.001 to 0.1%.Hagers marmes and gold chloride reagents were by

far least effective detecting reagent failing to react with 13 12 and 10 respectively of the 40 test

alkaloids. All 3 of the Mayers formulations were inferior to Valsers reagent with respect tosensitivity and specificity of alkaloid detection. It should be pointed out that the majority of these

precipitating reagents must be used to defect alkaloids only in acid solution. And further more.

That a large number of naturally occurring mononitrogenous plant principles will react to give

false-positive tests. These will be discussed subsequently .[66-72]

1.4.5.4 ALKALOID DETECTING REAGENTS EMPLOYED IN

SCREENING PROGRAMS:



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NAME OF REAGENT SURVEYS USED

Mayer reagent 39

Silicotungustic acid reagent 23

Dragondroffs drop reagent 19

Wagners reagent 11

Dragendroffs spray reagent 10

Sonnenscheins reagent 09

Hangers reagent 07

Bouchardats reagent 03

Phophotungustic acid 02

Valsers reagent 01

Chloroplatinic acid reagent 01

Chlorauric acid reagent 01

Sodium tetraphenylboron reagent 01

Table No. 3: Alkaloid detecting reagents employed in screening programs.

1.4.6 SCREENING FOR HETEROSIDE (GLYCOSIDES):

Heterosides arc organic compounds in which a hemiacetal linkage usually connects the

anomeric carbon of a sugar (glycone) with an alcohol or phenolic hydroxyl of a second nonsugar

molecule (aglycone) this type of linkage rise to the so-called o-heterosides (e.g.,salicin) the most



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common type of Heterosides found in plants If the anomeric carbon of the glycone is attached to an

aglycone through sulfur the S-heterosides are formed (e.g.,sinigrin) A third group are the N-

hcterosides which involve attachment of the glycone to an amino group of an aglycone

(e.g.vicine,crotnoside) Finally, the C-heterosides involve a carbon of carbon linkage of glycone and

aglycone (e.g.aloin).

As a general rule plant heterosides are easily hydrolyzed with dilute acids or appropriate

enzymes the C-hcterosides arc a notable ex-ception as they are resistant to the usual type of acid

hydrolysis and require ferric chloride for this purpose

A number of different sugars are known to occur in plants in combination with an equally

large number of diverse aglycones Paris has recently reviewed plant heterosides with particular

reference to the types and distribution in plats.

In most instances the biological activity of heterosides can be attributed to the aglycone

moiety the glycone is mainly associated with the degree or modification of activity primarily induced

by the aglycone. However the cardiac heterosides can be pointed out as a group that have no useful

biological activity unless the heteroside is intact thus we have the economically important saponin

heterosides and the medicinally useful anthraquinone flavonid cyanogenetic isothioyanate and cardiac

groups.

From a chemical point of view there are 3 parts of the heteroside molecule that can be used as

a material of detecting this group of compounds in plant material. First the hemiacetal linkage

between aglycone and glycol is usually not associated with biological activity, nor can it be

associated with any specific aglycone. This part of the molecule does not appear attractive as a means

of detecting plant heterosides. Because of the usual correlation of biological activity with the aglycone

moiety of heterosides and because this part of molecule often has chemical properties amenable to

ready detections, most investigator have used it as a means of screening plant material indirectly for

heterosides..[68,69,70,71,72]

1.4.6.1 Detection of Glycosides:

If, however, heterosides must be intact to exert their potential biological activity it

would appear most fruitful to detect the hemiacetal linkage in plant extracts as an identifying



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feature of the presence of heterosides. Several investigator have proposed application of those

to the screening of plants for hetersoidal attests to their complexity or inefficiency. Bourquelot

proposed a method for detecting and identifying hetersoidal based on the determination of an

Enzymolytic index of reduction obtain by measuring the optical reaction of a heteroside-

containing plant extract before and after hydrolysiswith specific enzymes. Although the method

has some value it is time consuming and requires large amounts of plant matcrial therclorc it

would be difficult to adopt to a large-scale screening program Bliss and Ramstad devised a

simple procedure that could be adapted for routine screening. It consists of :

(a) Separation of the heterosides in an extract by paper chromatography

(b) Hydrolysis of the heterosides on the chromatogram with proper enzymes (i.e.a-glucoidase-

invertin-Bglucosidase-emulsin) and

(c) Location of the reducing sugars formed on the chromatogram by means of an appropriate

reagent spray. This method appears to be least objectionable of many proposed. However it

will detect only those heterosides for which the selected enzymes have a hydrolytic specificity

Also optimal reaction conditions such as time temperature and pH would have to be determined

for a large number of substrate heterosides to propose operating conditions that would allow

detection of the greatest number of compounds. Janot et al and Paris have suggested

chromatographic methods for detecting heterosides similar to the method of Biss and Ramstad

but acid hydrolysis of the sample is induced to supplement the action of enzymes. Other

methods have been proposed ,but ether they have not been applied successfully to plant sample

or certain limiting factor make them of doubtful value for general screening.

Knapp and Beal have proposed a method involve the selective extraction of heterosides from

plant material using 80% ethanol oxidation of the free sugar in the extract to their

corresponding carboxylic acids so that they will not be detected after hydrolysis of the

heterosides hydrolysis of the heterosides in the extract using 0.15 N sulfuric acid and hart (100)

.

(d) Detection of hydrolyzed glycones by means of paper chromatography. The major objection

to this procedure is that holosides, especially sucrose which is wide spread in plants, are

detected thus the method is of decreased value.



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Abich and Reichstein have utilized a rather simple procedure which involves the

preparation of an extract devoid of free sugars hydrolysis of the extract with the Killani acid

mixture and testing of the hydrolysis products with Fehlingsolution for evidence of reduction.

These investigators have pointed out the nonspecificity of the test; however in a broad

screening program false-positive reactions must be accepted especially in the presence of a

completely acceptable and specific method of detection.

It does not appear that adequate methodology has been developed to allow for an

extensive screening of plants for hetrosides based on the approaches described above. As

indicated previously, the majority of studies involving a search for hetrosides in plant material

concerned with tests designed to detect specific aglycones. The more important of these willnow be considered. .[68,69,70,71,72]

1.4.6.2 Isolation of triterpinoid glycosides:

This study reports the isolation and characterization of a new triterpenoid glycoside

extracted from the bark of Terminalia Arjuna. The isolation of the organic compounds was

done using simple chromatographic technique. Compound characterization using various

spectroscopic technique identify the final isolated compound as Olean-di ol Dglucopyrano-side-oic acid. The method of isolation is simple, cost effective andefficient. The preliminary

bioactivity of the compound was also evaluated. .[68,69,70,71,72]

1.4.6.3 Extraction and isolation of glycosides:

The sun-dried stem bark was crushed into fine powder. Pulverized bark part 2.5 kg was

exhaustively extracted with ethanol (95%) at room temperature, 23 2 0C, for 10 days. The

ethanolic extract was filtered, distilled and concentrated to obtain the solid brownish residue

(M.P = 158 0C). The yield was 7.1% w/w. The final weight was noted and stored. The residue

was treated with water. The water soluble and insoluble portions were separately collected by

filtration (G4 crucibles). Initial study in preparative TLC of the

water-soluble part does not give any spot in the chromatogram and therefore, we did not take

any further attempt to analyze the water-soluble part.

The water insoluble alcohol extract was found to be partially soluble in different

organic solvents like ethyl acetate, benzene, chloroform, carbon tetrachloride and methyl



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alcohol. So, it was dissolved in ethyl alcohol and allowed to stand for nearly 4 h then filtered

and separated into ethyl alcohol soluble (A) and insoluble (B) parts.The ethyl alcohol soluble

(A) portion was treated with equal volume of distilled water and ethanol mixture (1:1) and then

treated with ethyl acetate in separating funnel, which separated into organic layer and the

aqueous layers. The process was repeated for at least

three times to ensure complete extraction From the organic layer taken separately, the ethyl

acetate was distilled out by and it was further treated with dry petroleum benzene and the purity

of the compound was tested using thin layer chromatographic system developed in a benzene

and ethyl acetate (9:1)solvent system. Three different spots were obtained when the

chromatogram was placed inside an Iodine chamber, indicating the presence of three differentcompounds. All the three compounds were separated and collected using preparative thin layer

chromatography.

However, we failed to get a quantitative yield of the materials and therefore, further

analysis of the compounds was not undertaken in the present investigation.The aqueous layer

obtained in the above process was treated with distilled water and filtered. In this case, the thin

layer chromatography developed in benzene and ethyl acetate (9:1) solvent system does not

yield any spot thus confirming absence of any compounds. The residue portion (B) was

refluxed with petroleum benzene for 12 h using reflux condenser and water bath. It was filtered

and separated into two parts, residue (C) and filtrate (D). The filtrate (D) was subjected to

preparative TLC and no spot was found, thus confirming absence of any compound. The

residue (C) was again refluxed with dry benzenefor 12 h and filtered. No residue was obtained

in this case. So, the benzene soluble portion was concentrated using a hot water bath to obtain a

greenish-white colored residue. This wasfurther treated with petroleum benzene mixture (9:1)

and recrystallized in benzene to give a white color compound (D), (M.P. = 160 - 162 oC), with

quantitative yield. .[68,69,70,71,72]

1.4.7 SCREENING OF ANTHRAQUINONES:

The largest groups of naturally occurring quinine substances are the anthraquinones.

Although they have a widespread use as dyes, their chief medicinal value is dependent upon their

cathartic action. They are restricted distribution in the plant kingdom and are found most

frequently in members of the Rhamnaceae, Polygonaceae, Rubiaceae, Leguminosae and

Liliaceae. As found in plant, they are usually carboxylated, methylated or hydroxylated



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derivatives of the anthracines, anthrone, anthranol, anthraquinone, or dianthrone. Hydroxylated

anthracines often occur as hetrosides linked with various sugars through one of the hydroxyl

group. Other types of anthracene hetrosides are represented as C-hetrosides in which the sugar

and aglycone are linked by a carbon to carbon bond. . [68,69,70,71,72]

1.4.7.1 Detection of anthraquinones:

For the qualitative detection of anthraquinones in plant material, the Brontrager reaction, as

modified by Kraus, appears to be simplest to perform in the application to phytochemical

screening. The powdered sample (0.3gm) is boiled for a few minute with 0.5 N KOIT (10ml) to

which is added 1 ml. of dilute hydrogen peroxide solution. After cooling the mixture is filtered

and 5 ml. acidified with 10 ml. of benzene in a separator and the benzene layer takes on a yellow

color . A 5-ml. sample of ammonium hydroxide and a positive reactive for the presence of

anthraquinones is evidence by the formation of a red color in the alkaline layer. normally if c-

glycosides are present in a sample being evaluated for anthra-quinones they will not be detected

by the usual Borntrager reaction as c-glycosides require special methods for cleaving the sugar

from the aglycone this can be done with ferric chloride sodium dithionate or as described above

with peroxide in an alkaline medium It has been shown that this method results in a mixture of

products however this is not a dosed vantage for a general screening test other simple and rapid

spot tests which involve the direct addition of a reagent to the solid sample (powdered drug) have

been described they should be useful in photochemical screening but to date have not been

shown to be ap-pliable for this type of work photochemical surveys for anthraquinones have

been found only infrequently in the plants .[68,69,70,71,72]

1.4.8 SCREENING OF TANNINS:

Two groups of phenolic constituents, hydrolysable and condensed, comprise the

tannins, substances which are important economically as agents for the tanning of leather and for

certain medicinal purpose. More recently, evidence has been presented in support of their

potential value as cytotoxic neoplastic agents. [73-80]



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1.4.8.1 Properties of tannins:

Hydrolysable tannins are yellow-brown amorphous substances which dissolve in hot

water to form colloidal dispersions. They are astringent and have the ability to tan hide.

Chemically speaking, they are esters which can be hydrolyzed by boiling with dilute acid to yield

a phenolic compound, usually a derivative of gallic acid, and a sugar. These are often referred to

as pyrogallol tannins.

Condensed tannins are polymers of phenolic compounds related to the flavonoids and are

similar in general properties to the hydrolysed tannins but are not very soluble in water and

following treatment with boiling dilute acid red-brown insoluble polymers known asphlabaphenes or tannins-red are formed. [74-84]

1.4.8.3 Extraction of tannins:

The process used to extract tannins is the hydrosolubilization because this process

operates with temperaturesaround 100C, the extraction process motives ahydro cracking of

sugar and others organic compounds with a darkening of the final product. We studied the

supercritical extraction process as alternative procedure to obtain the natural raw material to

leather tannage . In which supercritical carbon dioxide and polar ornon-polar co-solvents were

used as solvents. The advantages of supercritical extraction process withregard to

hydrosolubilization and solvent extraction are low extraction temperature, shortextraction time

and absence organic solvent concentration in the extract. Another objective wasto compare the

different extraction technology. [74-84]

1.4.8.2 Detection of tannins:

Tannins are detected most simply in plant extract by the use of the so called gelatin-block

test which has been utilized extensively in the phytochemical surveys. This test employs aqueous

extract prepared from 80% ethanol extracted plant material. A sodium chloride solution is added

to one portion of the test extract, of 1% gelatine solution to a second portion, and the gelatine

salt reagent to a third portion. Precipitation with the latter reagent or with both the gelatine and



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gelatine-salt reagents is indicative of the presence of tannins. If precipition is observed only with

the salt solution a false-positive test is indicated. Positive test are confirmed by the addition of

ferric chloride solution to the extract and should result in a blue, blue-black, green or blue-green

color and precipitate. Hoch has applied some 33 different classical tannin detecting reagents to

several tannin extract; however, the nonspecificity of many of these would render them

impractical for use in general phytochemical screening work. [74-79]

1.5 MATERIAL AND METHODS

1.5.1 Natural Material :

The raw material, black acacia bark, was provided by extratos brasil. A part of bark

was milled with cutting mill (TECNAL - Willye TE 650) with 2.0 mm average particle

diameter. In the solvent extraction with Soxhlet apparatus, dry natural material was employed.

The dryer used Pansera, M. R. et al. Brazilian archives of biology and technology 996 was a

biomatic equipment. The tannin was dried for 10 days at 36C.[85,86,87]

1.5.2 Raw material preparation :

Oilseeds and nuts should be properly dried before storage, and cleaned to remove sand,

dust, leavesand other contaminants. Fruits should be harvested when fully ripe, cleaned and

handled carefully toreduce bruising and splitting. All raw materials should be sorted to remove

stones etc. and especiallymouldy nuts, which can cause aflatoxin poisoning. When storage is

necessary, this should be inweatherproof, ventilated rooms which are protected against birds,

insects and rodents. Some rawmaterials (for example groundnuts, sunflower seeds) need

dehusking (or decorticating). Small manualmachines are available to give higher production

rates than manual dehusking . Dehusking is important to give high yields of oil and reduce the

bulk of material to be processed` but in groundnut oil extraction about 10% by weight of husk

should be added back to the nuts to allow oil to escape more freely from the press. [85,86,87]



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Figure 27: A decorticating machine

Coconut is dehusked and split by skilled operators as this is faster than the available small-scale

machines. Most nuts need grinding before oil extraction to increase the yield of oil. Small mills

are available for grinding copra, palm kernels and groundnuts.Some seeds (e.g. groundnuts) are

conditioned by heating to 80-90oC using a seed scorcher and all oil-bearing materials need to

have the correct moisture content to maximise the oil yield. Other oilseeds and nuts are usually

processed cold provided that their moisture content is below about 7%.[85,86,87]

1.5.3 Methods of oil extraction :

There are basically three methods of removing oil from the raw materials: solvent

extraction,wet processing or dry processing. Solvent extraction is not suitable for small-scale

processing because of high capital and operating costs, the risk of fire and explosions from

solvents and the complexity of the process. Equipment for wet or dry processing is available at

different scales of operation from household to industrial scale. Traditional methods of

extraction are described below, followed by higher output manual machines and mechanized

extraction.

1.5.3.1 Traditional methods:



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Oil is extracted from fresh coconut, olives, palm fruit shear nut etc. by separating the flesh and

boiling it in water. Salt is added to break the emulsion and the oil is skimmed from the surface.

In palm oil processing the fruit is first heated in a digester.

[85,86,87]

1.5.3.2 Manual methods:

Oil can be extracted by pressing softer oilseeds and nuts, such as groundnuts and shea nuts,

whereas harder, more fibrous materials such as copra and sunflower seed are processed using

ghanis. Pulped or ground material is loaded into a manual or hydraulic press to squeeze out the

oil-water emulsion. This is more efficient at removing oil than traditional hand squeezing,

allowing higher production rates.Fresh coconut meat is removed from the shell using a manual

reamer or a motorised reamer. The fine particles are pressed in a similar way to extract the oilemulsion. The emulsion is broken and the oil is then separated and clarified .

Presses have a number of different designs, which can be grouped into screw or

hydraulic operation. Both types can be manual or motor driven. In all types, a batch of raw

material is placed in a heavy-duty perforated metal cage and pressed by the movement of a

heavy metal plunger. The amount of material in the cage varies from 5-30 kg with an average

of 20kg. Layer plates can be used in larger cages to reduce the thickness of the layer of raw

material and speed up removal of oil. The pressure should be increased slowly to allow time for the

oil to escape. Screw types are more reliable than hydraulic types but are slower and produce less

pressure. Except where a lorry jack is used .[85,86,87]

Figure 28: A seed scorcher Figure 29: A manual reamer

Hydraulic types are more expensive, need more maintenance, and risk contaminating oil with

poisonous hydraulic fluid.



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Figure 30: Hydraulic oil expeller

Ghanis are widely used in Asia but less so in other areas. A heavy wooden or metal pestle is

driven inside a large metal or wooden mortar . The batch of raw material is ground and pressed

and the oil drains out. They have relatively high capital and maintenance costs and need skilled

operators to achieve high oil yields. [85,86,87]

Figure 31: Animal powered extraction Figure 32: Motorized extraction

1.5.3.3 Motorized Extraction:



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Motorized presses are faster than manual oranimal types but are more expensive.

Motorised ghanis are also available, but their higher capital and operating costs require a larger

scale of production for profitability.

Expellers are continuous in operation and work by grinding and pressing the raw

material as it is carried through a barrel by a helical screw . The pressure inside the barrel, and

hence the yield of oil, are adjusted using a choke ring at the outlet. The equipment has higher

production rates than similar sized presses but is more expensive to buy and operate.

Figure 33: Powered oil expeller Figure 34: Manual oil expeller

Although manual expellers are available , small scale oil millers more often use

powered equipment to reduce the time and labour involved in processing. Some designs also

have an electric heater fitted to the barrel to increase the rate of oil extraction. The production

rate using presses and ghanis depends on the size of the equipment and the time taken to fill,

press and empty each batch. The production rate of expellers depends on the size of the

equipment, the speed of the screw and the setting of the choke ring. [85,86,87]

1.introduction complete

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