schiff bases as an antimicrobial agent: a reviewschiff bases derived from o phthalaldehyde (opa) and...

Journal of Biological and Chemical Sciences (JBCS) Rani et al, (2015) vol.2, no. 1, 62-91

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Schiff bases as an antimicrobial agent: A review

Anita Rani1*, Manoj Kumar1, Rajshree Khare2 and Hardeep Singh Tuli3

1Department of Chemistry, Maharishi Markandeshwar University, Sadopur, Ambala

2Department of Chemistry, Maharishi Markandeshwar University, Mullana, Ambala

3Department of Microbiology, Kurukshetra University, Kurukshetra

*Correspondence at: [email protected]

Received: April 16, 2015; Accepted: May 23, 2015

Abstract

Schiff bases are versatile ligands and known to be synthesized from the condensation of an

amino compound with carbonyl compounds. These compounds along with their metal complexes

are considered to be an important as catalysts in various biological processes. Also Schiff base

complexes are gaining popularity among the various industries including polymers, dyes and

pharmaceutical. This review summarizes the applications of Schiff bases and their complexes as

potent antimicrobial agents.

Key words: Schiff bases, metal complexes, antimicrobial agent.

Introduction

The first preparation of imines was reported in the 19th century by Hugo Schiff [1- 3]. The

synthesis reported by Schiff involves the condensation of a carbonyl compound with an amine

under azeotropic distillation. A Schiff base is a nitrogen analog of an aldehyde or ketone in

which the C=O group is replaced by C=N-R group as shown in Scheme [1]. It is usually formed

by condensation of an aldehyde or ketone with a primary amine [2-4].

The formation of a Schiff base from an aldehydes or ketones is a reversible reaction. Schiff bases

derived from an amino and carbonyl compound are an important class of ligands that coordinate

to metal. In azomethine derivatives, the C=N linkage is essential for biological activity, several

azomethines were reported to possess remarkable antibacterial, antifungal, anticancer and

diuretic activities. Schiff bases have wide applications in food industry, dye industry, analytical

ISSN 2394-9139 (P), 2394-9147 (O) Review article


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chemistry, catalysis, fungicidal, agrochemical and biological activities. However with growing

incidences of infectious diseases, there has been increasing emphasis on the screening of new

and more effective antimicrobial drugs with low side effects. Schiff base complexes are

considered to be among the most important stereochemical models in main group and transition

metal coordination chemistry due to their preparative accessibility and structural variety. A

considerable number of Schiff base complexes have potential biological interest, being used as

more or less successful models of biological compounds. They have not only played a seminal

role in the development of modern coordination chemistry, but also considered as key points in

the development of inorganic biochemistry, catalysis and optical materials. The present review

describes the current updates in the synthesis of Schiff base compounds.

R NH2R C R

O

C N R

R

R

H2O

Scheme 1

Where R, may be an alkyl or an aryl group. Schiff bases that contain aryl substituent are

substantially more stable and more readily synthesized, while those which contain alkyl

substituents are relatively unstable. Schiff bases of aliphatic aldehydes are relatively unstable and

readily polymerizable while those of aromatic aldehydes having effective conjugation are known

to be more stable.

Areas of Applications of Schiff Bases:

Nitro and halo derivatives of Schiff bases are reported to have antimicrobial and

antitumor activities. Antimicrobial and antifungal activities of various Schiff bases have


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also been reported. Some derivative of Schiff base & Beta- Lactam acts as good

antimicrobial agents [5].

Schiff base ligand & metal complexes of sulphur & nitrogen acts as good antibacterial

agents [1, 6].

The crown ethers of shiff bases are also examined to have a very good potential to act as

anti microbial agent [7].

Some Schiff base Copper (II) complexes with phenanthroline and bipyridyl shows better

antifungal activity to control the fungal diseases in human and plants [8].

Thiazole containing Schiff’s bases and their transition metal complexes were shown to be

extensive range of biological activities.

In a similar way there are many compounds of Schiff base with transition metals that

shows a wide range of antimicrobial activity [10-12].

The order of increasing activities is ligand < MeSnL < PhSnL < BZ3SnL, the results

matched with the previously reported data for the biological activity of organotin

complexes [13].

Fakruddin & co worker synthesized Schiff base metal complexes of Cr(III), Co(II), Ni(II) and

Cu(II) derived from 2, 6-pyridine dicarboxaldehyde-Thiosemicarbazone (PDCTC) by

conventional as well as microwave methods. In conventional method the metal complexes was

prepared by the mixing of equal moles of metal salts dissolved in the methanol followed by

addition of NaOAc (metal: ligand)in 1:1ratio. The precipitated complex was, filtered washed

with ether and recrystallized with ethanol and dried under the reduced pressure over anhydrous

CaCl2 in a desiccator while in microwave method the ligand and the metal salts was mixed in

1:1 (metal: ligand) ratio in a grinder. The Schiff base and metal complexes displayed good

activity against the Gram-positive bacteria Staphylococcus aureus, the Gram-negative bacteria

Escherichia coli and the fungi Aspergillus niger & Candida albicans. The antimicrobial results

also indicated that the metal complexes displayed better antimicrobial activity as compared to the

Schiff bases ligand. Chelation tends to make the ligand act as more powerful (Fig. 1) and potent

bactericidal agent [14].


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Fig. 1 [metal complexes obtained from 2, 6-pyridine dicarboxaldehyde-Thiosemi carbazone

(PDCTC) synthesized by Fakruddin & co worker in 2014].

Similarly they Synthesis another Novel Metal Complexes with Schiff Base 2, 5-Thiophene

Dicarboxaldehyde-Thiosemi carbazone from 2,5-Thiophene dicarboxaldehyde-Thiosemi -

carbazone(TDATC) by conventional as well as microwave methods. The Schiff base and metal

complexes displayed good activity against the Gram- positive bacteria Staphylococcus aureus,

the Gram- negative bacteria, Escherichia coli and the fungi Aspergillus niger [15].

R. Selwin Joseyphus & co worker prepared Schiff base ligands metal complexes with Zn(II). The

Zn(II) complex was prepared by dissolving Zn(II) nitrate with ligand in methanol [16].The in

vitro biological screening effects of the investigated compounds were tested against the bacterial

species Staphylococcus aureus, Escherichia coli, Klebsiella pneumaniae, Proteus vulgaris and

Pseudomonas aeruginosa and fungal species Aspergillus niger, Rhizopus stolonifer, Aspergillus

flavus, Rhizoctonia bataicola and Candida albicans by the disc diffusion method (Fig.2).

N

N N

HH

NH NH

N N

H H

N

S S

M


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Fig. 2 [Schiff base metal complex formed after condensation of glycylglycine with indole-3-

carboxaldehyde. Synthesized by R. Selwin Joseyphus & co worker in 2008]

Pillutla Sambasiva et al Synthesize & characterize the antimicrobial activity of tridentate Schiff

base ligands containing pyrazolone moiety and their transition metal complexes of VO(II),

Cu(II), Fe(III), and Co(II). The metal complexes of these ligands with VO(II), Cu(II), Fe(III),

and Co(II) show varying geometries. (Fig. 3-5).The ligands and metal complexes show extensive

antibacterial and antifungal activity. In general Fe(III) and Co(II) complexes are more potent

than other complexes and ligands. The complexes show enhanced antibacterial and antifungal

activity against various microbscompared to the ligands[17].


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N

N

N X

OH

Fig. 3 [Schiff base ligand was prepared by reacting 3-methyl-1-phenyl-4-acetylpyrazolin -5-

ol with 1,2-diaminobenzene, and 2-aminophenol by Pillutla Sambasiva et al in 2010]

Fig. 4 [Metal complex of above Schiff base ligand prepared by Pillutla Sambasiva et al in

2010]

N

N

N

O

N H 2

V

O C H 3

H

O


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N

N

N

O

NH2

Cu

H2N N

N

N

O

Fig. 5 [Condensation of two molecules of given ligand to form a new metal complex

synthesized by Pillutla Sambasiva et al in 2010]

M. B. Fugu et al [18] prepared transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and

Zn(II) with Schiff base ligand .The Schiff base ligand was prepared by condensation of vanillin

with 2-aminophenol in ethanol. Schiff base metal (II) complexes was prepared by adding drop

metal(II) salts [MnCl2.4H2O, CoCl2.6H2O, NiCl2.6H2O, Cu(CH3COO)2.H2O and

Zn(CH3COO)2.2H2O] in boiling ethanol( Fig. 6). The Schiff base ligands and the metal

complexes were assayed with the bacteria Escherichia coli, Salmonella typhi, Klebsiella

pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Streptocuccus pyogenes,

Corynebacterium specie, and Basillus subtilis using disc diffusion method. The metal complexes

were found to be more effective against these micro organisms.


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HO

N

CH

O

OH CH3

O

CH

N

OH

M

CH3

X

X

OH

Fig. 6 [Schiff base metal complex prepared by condensation of vanillin with 2-aminophenol

in ethanol with metal solution given by M. B. Fugu et al in 2013]

K. R. Joshi & co workers [19] synthesized Schiff Base Metal Complexes from 2 -Hydroxy-3-

methoxy-5-nitrobenzaldehyde & newly synthesized compound was tested for their antibacterial

activities & found to be very affective. Neelakantan et al, synthesized Metal complexes with

Schiff bases derived from o phthalaldehyde (opa) and amino acids viz., glycine (gly) l-alanine

(ala), l-phenylalanine (pal) [20]. The antimicrobial activities of the Schiff base metal complexes

were tested in vitro against eleven microbes by the modified disc diffusion method. Cu(II) and

Ni(II) complexes exhibit inhibition towards all the studied microorganisms. However, Co(II) and

Mn(II) complexes exhibit less inhibition and VO(II) complexes have no activity towards the

microorganisms. Four new N2O2 type tetradentate Schiff base complexes of Co(III), derived

from the condensation of meso-1,2 diphenyl-1,2-ethylenediamine (mesostilbenediamine) with

salicylaldehyde derivatives, were synthesized [20]. The in vitro antimicrobial activity of the

Schiff base complexes was tested against various human pathogenic bacteria [Fig.7].


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N

OH

N

O

Co

Py

Py

PF6

Fig. 7 [Schiff Base Metal Complexes derived from 2 -Hydroxy-3-methoxy-5-

nitrobenzaldehyde synthesized by K.R.Joshi and co-worker in 2007]

Pallavi Goel & co workers [21] synthesized schiff base ligand & their transition metal complex

(Mn (II),Cu (II),Co(II) & appropriate balance between broad spectrum pharmacological profile.

Tetradentate macrocyclic ligand [1,2,5,6tetraoxo-3,4,7,8 tetraaza-(1,2,3,4,5,6,7,8) tetrabenzene]

and its transition metal complex of Mn(II) [Fig. 8]. The LD50 values of the ligand and its metal

complex has been. The screened antimicrobial Activity also examined against different bacteria

and plant fungi. The result was showing that macrocyclic ligand was potentially more active

towards tested microbial species than metal complex.


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Fig. 8 (Mn(II) complex of 1,2,5,6tetraoxo-3,4,7,8tetraaza- (1,2,3,4,5,6,7,8) tetrabenzene

synthesized by Pallavi Goel & co workers in 2014).

Another example is Tetraaza macrocyclic Cu(II) complexes of composition [CuLX2] (where L =

N4 donor macrocyclic ligands) and (X = Cl−, NO3−). The biological activity of all the

complexes against gram-positive and gram-negative bacteria was compared with the activity of

existing standard antibacterial drugs like Linezolid and Cefaclor [Fig. 9]. Metal complexes were

found to be most potent against both gram-positive as well as gram-negative bacteria due to the

presence of thio group in the parent ligands [21].

Fig.9 [Cu(II) complex of Tetraaza macrocyclic ligand prepaired by Pallavi Goel & co

workers in 2014.

NH

HN

O

O

NH

HN

O

O

Mn

X

X

N

N

NH

HN

O

O

NH

HN

N

N

Cu

Cl

Cl


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Ajay R. Patil & co workers [22] synthesized Co(II) complexes of Schiff base 2-amino-4-

nitrophenol-N-salicylidene with some amino acids. The Schiff base and mixed ligand complexes

were preliminary scanned against various strains of microbes to study their biological effect [Fig.

10]. It has been observed that the compounds showed very good antibacterial and antifungal

activity. In comparison with the activity of ligand, activity of the metal complexes was more.

This indicated that activity increases with introduction of metal ion. The compounds showed

very good antibacterial and antifungal activity at 12.5, 25, 50, 100 and 200 ppm.

N

Co

O

NO2

HO

H

H2N

O

C

H R

O

Fig. 10 [Co(II) complexes of Schiff base 2-amino-4-nitrophenol-N-salicylidene with amino

acids was prepaired by Ajay R. Patil & co workers in 2012]

Benedict O Achugbu & co workers synthesized metal(M(II)) complexes of the Schiff base 2-(6-

methoxybenzothiazol-2-ylimino)methyl)-4-nitrophenol and characterized. The complexes

mostly exhibit good in-vitro antibacterial activities against S. aureus, E. coli and P. mirablilis

with inhibitory zones range of 16.0-27.0 mm, 13.0-15.0 mm and 17.0-20.0 mm respectively [23].

N.K. Chaudhary & co workers [24] prepared novel Schiff base ligand by condensation of 2-

aminophenol with furan-2- Carbaldehyde using distilled ethanol. The resulting solution was

allowed to evaporate by slow diffusion process in air for a week. The crystals of novel ligand

were collected, washed several times with distilled ethanol and recrystallized from hot ethanol.


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Then to make a metal complex the synthesized novel ligand in hot ethanol was added to hot

ethanolic solution of metal chlorides drop wise to make Ni(II) & Cu(II) complexes. A good

crystalline form of the complexes was obtained. Physical and analytical data suggest that the

Schiff base acts as tridentate ligand towards metal ions via azomethine-N, deprotonated-O of 2-

aminophenol and O-atom of furan moiety. The synthesized ligand, along with its metal

complexes were screened for their in-vitro antibacterial activity against four bacterial pathogens

(E. coli, Bacillus subtilis, Staphylococcus aureus and P. vulgareous ). The results of these studies

revealed that the free ligand and its metal complexes showed significant antibacterial potency

[Fig. 11].

K. S. Prasad & co workers synthesized and characterized Novel oxovanadium(IV) complexes

with 2-methyl-3-(pyridine-2-ylmethyleneamino)quinazolin-4(3H)-one or3-(2-hydroxy-3-

methoxybenzy lidene amino)-2-methylquinolin-4(3H)-one by elemental analysis [25].The

synthesized compounds were tested for antimicrobial activity by disc diffusion method. The

results indicate the enhanced activity of metal complexes over their parent ligands. The DNA

binding and nuclease activity of the synthesized compounds were also studied. The investigation

of the interaction of the complexes with calf thymus DNA has been performed with absorption

spectroscopy which showed that the complexes are avid binders of calf thymus DNA [Fig. 12].

Fig. 11[Schiff base Nickel complex prepaired using 2-aminophenol with furan-2-

Carbaldehyde by N.K.Chaudhary & co workers in 2013]

N

O

H C

O

O

C H

N

N iO


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N

N

O

N C

N

H

N

C

H

N

N

N

O

V

O

Fig.12 [oxovanadium(IV) complexes with 2-methyl-3-(pyridine-2-

ylmethyleneamino)quinazolin-4(3H)-one or3-(2-hydroxy-3-methoxybenzy lidene amino)-2-

methylquinolin-4(3H)-one, a schiff base metal complex synthesized by KS Prasad & co

workers in 2011]

K. Siddappa & co workers [26] synthesized a new compound named 3-2-(1-(1-

Hydroxynaphthalene-2-yl) Methylene amino) Phenyl) -2-Methylquinazoline-4 (3H) from hot

ethanolic solution of 3-(2-aminophenyl)-2-methylquinazolin-4(3H)-one by adding in ethanolic

solution of 2-hydroxy-1-naphtholdehyde. A general method has been used for the preparation of

complexes using the reaction of metal salts and the corresponding Schiff-base. A methanolic

solution of ligand and Cu(II), Ni(II) Co(II), Mn(II) and Zn(II) chlorides was mixed gently and

refluxed for 3 h. The complex shows good antioxidant, antitubercular and antimicrobial activities

[Fig. 13].The antibacterial and antifungal activities of the ligand and its complexes were tested


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against two gram-positive bacteria such as Staphylococcus aureus Bascillus subtilis, one gram-

negative Escherichia coli and two fungi Aspergillus niger and Aspergillus flavus & results were

found to be positive.

N

N

O

CH3

NC

H

C

HN

N

NCH3

O

O

O

M

Fig. 13 [Shiff base metal complex of 3-2-(1-(1-Hydroxynaphthalene-2-yl)

Methylene amino) Phenyl) -2-Methylquinazoline-4 synthesised by K.

Siddappa& co workers in 2013.]


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Eddie L. Chang & co workers Synthesized Schiff base of Cobalt Complexes containing a new

hybrid amine-imine-oxime ligand derived from the condensation reaction of diacetylmonoxime

with benzidine [27], & found to be effective against Bacillius subtilis [Fig. 14]. However the

same complex showed no activity towards Staphylococcus aureus or the Gram-negative bacteria

Escherichia coli and Enterobacter fecalis.

NH2 N N O-

N N NH2OH

CH3 CH3

CH3 CH3

Co LL

Fig. 14 [Cobalt Complexes of Schiff base with amine-imine-oxime ligand prepaired by

Eddie L. Chang & co workers in2010]

Mahalakshmi & co workers [28] derived the binuclear Schiff base complexes are formed newly

using different transition metals at their stable oxidation state as Cu(II), Ni(II), and VO(II).

3,3′,4,4′-tetraminobiphenyl and 2-aminobenzaldehyde were condensed to form a new Schiff base

ligand having an two N4 group responsible for better chelating to the metal centers(Fig. 15). The

free ligand and their metal complexes were screened for their antimicrobial activities against the

following species: Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus. A

comparative study of minimum inhibitory concentration (MIC) values of the Schiff base and its

complexes indicate that the metal complexes exhibit higher antibacterial activity than the free

ligand. As the test solution concentration increases, the biological activity also increases. The

minimum inhibitory concentration (MIC) values of the investigated compounds are summarized.


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The observed MIC values indicate that the complexes have higher antimicrobial activity. The

metal complexes Cu(II), Ni(II) and VO(II) have higher antimicrobial activity than the ligand.

H2N N

M

NH2N N NH2

M

N NH2

4

2 SO42-

Fig. 15 [Cu(II), Ni(II), and VO(II) schiff base complexes were prepaired by condensing

3,3′,4,4′-tetraminobiphenyl and 2-aminobenzaldehyde by Mahalakshmi & co workers in

2014]

Shakir M. Alwan & co workers made an interesting approach of synthesizing a new series of

pyridopyrimidine derivatives containing Schiff bases of certain amino acids [29]. The new

derivatives were synthesized by reacting 3-formyl-2H-pyrido pyrimidine-2, 4 (3H)-dione with

glycine, alanine, glutamic acid, histidine, tryptophan or leucine in methanol under reflux using

glacial acetic acid as catalyst. The Schiff bases showed good to moderate antibacterial activity

against the test microbes. Compounds showed also antifungal activity [Fig 16]. Compounds

showed reasonable activity against p. aurogenosa and C. albican, while it showed a good

activity against E. coli and no activity against G(-) bacteria. Compound showed a moderate

activity against E. coli and a good activity against Candida albicans. However, the Schiff bases

of the aromatic amino acids, showed better antimicrobial activities compared with those of

aliphatic amino acids.


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S.M.S.Shariar co workers [30] synthesized Schiff base Benzophenone Thiosemicarbazone

derived from thiosemicarbazide and Benzophenone & the compound was used to study their

antibacterial activities against some pathogenic bacteria by disc diffusion method. Benzophenone

thiosemicarbazone showed significant antibacterial activity as compared with that of Kanamycin.

The compounds was found to possess cytotoxic effect. Minimum inhibitory concentration of this

compound was also determined [Fig. 17]. The antibacterial activities of this compound were

measured in terms of zone of inhibition. The test compounds showed a good sensitivity against a

number of pathogenic bacteria.

D. Nasrin & co workers [31] in view of the antimicrobial activity of a series of nickel, copper

and zinc complexes of tridentate Schiff base derived from the condensation reaction of S-

benzyldithiocarbazate with 2- hydroxyacetophenone have been synthesized and found to be

potential antimicrobial agents. An attempt is also made to correlate the biological activities with

geometry of the complexes. The synthesized compounds have been evaluated for their

antibacterial and antifungal studies [Fig. 18]. The in-vitro biological screening effects of the

investigated compounds were tested against the bacterial species Shigella dysenteriae,

Salmonella typhi and Bacillus cereus and fungal species Fusarium equiseti, Macrophomina

phaseolina, Botrydiplodia theobromae and Alternaria alternate.

Karim Akbari Dilmaghania & co worker condense 5-(4-aminophenyl)-4-phenyl-1,2,4-triazole-

3-thione with 4-methoxy benzaldehyde in methanol which results in production of new Schiff

base [32].The synthesized compound were tested for their antimicrobial activity against bacterial

(Gram negative and Gram positive) strains in-vitro. The synthetic compound showed different

inhibition zones against tested bacterial strains [Fig. 19].The compound showed significant

antiproliferative activity against Acinetobacter calcoaceticus. Gajendra Kumari & co workers

[33] synthesized and characterized M(III) complexes of Cr, Mn and Fe with a Schiff base

derived from 2-amino-4-ethyl-5-hydroxybenzaldehyde and thiocarbohydrazide by several

techniques. The Schiff base ligand and the complexes were also tested for their antimicrobial

activity (against the bacteria Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa

and Bacillus megaterium, and the fungi Kluyveromyces fragilis, Rhodotorula rubra, Candida


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albicans and Trichoderma reesei) to assess their inhibiting potential[Fig 20]. An attempt was

also made to correlate the antimicrobial activity with the geometry of the complexes. All

complexes were found to be less active against the pathogens E. coli, S. aureus and

P.aeruginosa. The Cr(III) complex showed the best antimicrobial activity, but the ligand alone

was found to be active against the fungus T. reesei.

Fig. 16 [Schiff base ligand prepared by reacting 3-formyl-2H-pyrido pyrimidine-2, 4 (3H)-

dione with certain amino acids, Synthesized by Shakir M. Alwan & co workers in 2014]

C N N

H

C

S

NH2

Fig. 17 [Schiff base Benzophenone Thiosemicarbazone synthesized by S.M.S.Shariar co

workers in 2014]

N N

N

C

OHO

H R

COOH


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OH

C N

N

H

C

S

SCH2C6H5

CH3

Fig. 18 [Schiff base ligand obtained from condensation reaction of S-benzyldithiocarbazate

with 2- hydroxyacetophenone by D. Nasrin & co workers in 2013]

N

N

N S

Ph

H

N

H

R

R= 4 MeOC6H4

Fig. 19 [Schiff base ligand prepaired from 5-(4-aminophenyl)-4-phenyl-1,2,4-triazole-3-

thione with 4-methoxy benzaldehyde by Karim Akbari Dilmaghania & co worker in 2009]


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HO

C2H5

C

NH2

N

H HN

C

NH

N

S

C

H

NH2

OH

C2H5

M

H

2+

Fig. 20 [Schiff base metal M(III) complexes of Cr, Mn and Fe derived from 2-amino-4-

ethyl-5-hydroxybenzaldehyde and thiocarbohydrazide by Gajendra Kumari & co workers

in]

Azza A.A. Abou-Hussein & co worker [34] synthesized mono- and bi-nuclear acyclic and

macrocyclic complexes with hard-soft Schiff base ligand derived from the reaction of 4,6-

diacetylresorcinol and thiocabohydrazide. The Schiff base ligand and its metal complexes were

evaluated for their antimicrobial activity against one strain Gram-positive bacteria S. aureus and

P. fluorescens as Gram-negative bacteria as well as one pathogenic fungus, as F. Oxysporum.

The data were compared with standard antibiotics, chloramphencol as Gram-negative and

Cephalothin as standard reference for Gram–positive bacteria (Fig. 21). Cycloheximide was used

as antifungal standard reference. The in vitro antibacterial and antifungal activities demonstrated

that the complexes have higher antimicrobial activity in comparison with that of the ligand.

Farukh Arjmand & co -workers [35] has been synthesized the ligand by the condensation

reaction of 2-mercaptobenzimidazole and diethyloxalate. The ligand was allowed to react with

bis(ethylenediamine)CuII/ NiII complexes to yield complexes [Fig. 22].The antibacterial and

antifungal studies of the synthesized compounds were carried out against S. aureus, E. coli and


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A. niger. All the compounds tested, was found to be the most active against bacterial and three

fungal pathogens.

HO OH

N N

HN NH

S S

HN NH

N N

OHHO

Ru

Ru

Cl Cl

ClCl

Cl

Cl

Fig. 21[Schiff base metal (Ru) complex synthesized from 4,6-diacetylresorcinol and

thiocabohydrazide by Azza A.A. Abou-Hussein & co worker]

NSH

C

C

N

N

N

N

M

NH

NH

SH

Cl2

Fig.22 [Schiff base derived from condensation of 2-mercaptobenzimidazole and

diethyloxalate by Farukh Arjmand & co –workers in 2013]


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Anju Das Manikpuri & co workers Synthesis Schiff bases of Salicaldehyde and sulfonamides by

adding ethanol solution containing few drops of glacial acetic acid in to Salicaldehyde in which

sulphonamide was added slowly with constant stirring [35].The Schiff bases were screened for

the biological significance. The antimicrobial screening of duly characterized Schiff bases was

performed using paper disc method against some pathogenic strains of Salmonella entritidis and

Staphylococcus aureus (Fig. 23). Schiff bases showed significant results against S.enteritidis.

While studying the effects of concentration on zone of inhibition of each compound, the novel

Schiff bases gave excellent response against S. aureus at all chosen concentration.

N

OH

S

NH

R

O O

Fig. 23 [Schiff bases derived from Salicaldehyde and sulfonamides by Anju Das Manikpuri

& co workers in 2010]

Elsayed & co worker synthesized, characterized and evaluated biological activity of Co(II)

complexe of Schiff base Ligand Derived From Sulphadiazine and its antimicrobial activity was

found to be higher against Escherichia coli, Bacillus subtilis (G+) & Aspergillus niger and

Trechodenma viride [36]. Since, Gram-negative bacteria are considered a quantitative

microbiological method testing beneficial drugs in both experimental and clinical tumour


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chemotherapy [Fig. 24]. Therefore it has been claimed that, the synthesis of these complexes

might be established a new line for search to new antitumour agents.

O

N

Co

S

NH

N N

O

O

O

O N

CH3

O

O

H2O

CH2

Fig.24 [Metal complexes Schiff bases derived from sulfagundine with Co (II) was

synthesized by Badr A. Elsayed & co worker in 2014]

Gomathi Vellaiswami & co workers [37] synthesized a novel Schiff base from 3 ethoxy salicy

aldehyde & sulpha pyridine. The orange coloured solid mass formed during refluxing was

cooled, filtered, washed and dried in a desiccator. The prepared Schiff base was characterized

and it was found that it exhibited promising antibacterial and antifungal activity against various

microorganisms [Fig. 25].

N

HN S N HC

OH

OCH2CH3

OO

Fig. 25 [Schiff base ligand , 4-(3-ethoxy-2-hydroxybenzylideneamino)-N-(pyridin-2-

yl)benzenesulfonamide prepaired from sulfapyridine and 3-ethoxysalicyl aldehyde

synthesized by Gomathi Vellaiswami & co workers in 2014]


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A.V.G.S. Prasad & co-workers synthesized Schiff base from 2-thiophene- carboxy- aldehyde and

2-nitro benzoic acid. Metal complexes of the Schiff base were also prepared from salts of Mn (II)

and Co (II) in an alcoholic medium. The chemical structures of the Schiff-base ligand and its

metal complexes were confirmed by various spectroscopic studies [Fig. 26]. The free Schiff base

and its complexes have been tested for their antibacterial as well as antifungal activity by using

disc diffusion method and the results discussed. The experimental results suggested that Schiff

base derivatives are more potent in antibacterial and antifungal activities [38].

COOH

N C

SH

Fig. 26 [Schiff base derived from 2-thiophene- carboxy- aldehyde and 2-nitro benzoic acid

by A.V.G.S. Prasad & co-workers in 2014]

Conclusion

Schiff bases and their derivatives are a class of compounds with vast evidence from literature

evidence about pharmacological potential. Schiff base compounds have been shown to be

promising leads for the design of more efficient antimicrobial agents. Concisely, Schiff bases are

among the molecules which have therapeutic potential for the treatment of various human

diseases. Hence there is strong need to explore the molecular aspects of mechanism of actions of

various pharmacological mediated affected by Schiff base complexes so that we can use a huge

range of antimicrobials.

Acknowledgments

The authors would like to acknowledge M.M University, Sadopur (Ambala) for providing the

requisite facilities to perform this study.


86 Scienceindoors

Conflict of interest statement

There are no potential conflicts of interest among the authors regarding the publication of this

manuscript.

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schiff bases as an antimicrobial agent: a reviewschiff bases derived from o phthalaldehyde (opa) and...

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