Plant Pigments

Chromatography

Gary Stacey Lab

Teacher workshop, March 8, 2014

University of Missouri

Division of Plant Sciences

Plant pigments

Pigments - chemical compounds which reflect only certain

wavelengths of visible light

-appear "colorful“ (flowers, corals, animal skin contain pigments which give

them their colors)

-their reflection of light is the ability of pigments to absorb certain

wavelengths

Chlorophylls, carotenoids, anthocyanins

Plant pigments related to the light spectrum

Chromatography (from Greek χρῶμα chroma "color" and γράφειν graphein "to write")

= color separation

Paper chromatography

-> Pigments from plant tissues are separated

based on those chemical properties

(i.e., molecular size/solubility/polarity)

pigments

Photosynthetic Pigments - Chlorophylls

In most plants, two types are present:

Chlorophyll A and Chlorophyll B

Both types act as electron-transporters

in photosynthesis and give plants

their green color

Both are polar

Carotenoids and associated

xanthophylls:

- act as accessory pigments and trap

sunlight energy for photosynthesis.

- act as photo-protective agents,

protecting the plants from the effects

of excess energy build up that causes

the formation of toxins in plants

- anti-oxidants, precursor for vitamin

A formation, good for vision

maintenance

Carotenoids

Carotenoids and xanthophylls

- tetra-terpenes

- are non-polar

- represent more 60 pigments

Carotenoids

Anthocyanin

Anthocyanins:

- generate colors in red to blue range for

plants

- protect plants against UV light and

damage caused by UV

- attract insects for pollination and provide

protection against predators

- positive effects against cancer, aging and

neurological diseases, inflammation,

diabetes, bacterial infection

- bacterial infections

Anthocyanins

- phenolic pigments

- are polar

- water soluble

Anthocyanins

Chromatography (from Greek χρῶμα chroma "color" and γράφειν graphein "to write")

= color separation

Paper chromatography

-> Pigments from plant tissues are separated

based on those chemical properties

(i.e., molecular size/solubility/polarity)

pigments

Retention factor (Rf) values

of pigments

Rf =𝑫𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒑𝒊𝒈𝒎𝒆𝒏𝒕 𝒕𝒓𝒂𝒗𝒆𝒍𝒆𝒅

𝑫𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒔𝒐𝒍𝒗𝒆𝒏𝒕 𝒕𝒓𝒂𝒗𝒆𝒍𝒆𝒅=

𝒂

𝒃

Chromatography Background

a

b

Rf values of pigments

Carotene - 0.98; orange

Pheophytin - 0.81; olive green

Chlorophyll a - 0.59; blue-green

Chlorophyll b - 0.42; yellow-green

Anthocyanins - between 0.32 and 0.62; red, pink, purple

and blue colors

Xanthophyll 1 - 0.28, yellow

Xanthophyll 2 - 0.15, yellow

www.bioquest.org/summer2008/projectfiles/leafchromat

ography.doc

Chromatography Background

Chromatography Background

It is possible to measure the solubility of a pigment in a

solvent by measuring how far the pigment travels vs. how far

the solvent travels

This is called retention factor, or Rf value

Rf values are characteristic of specific pigments and can be

used to identify them

The higher the Rf value, the less polar the compound.

Thus, a compound not migrating from the origin would have

an Rf of 0, a compound migrating with the solvent front would

have an Rf of 1.0, and a compound migrating half as far as the

solvent front would have an Rf of 0.5.

Other applications

e.g., beverages, paint, pen ink, etc.

References

http://warnell.forestry.uga.edu/service/library/index.php3?docID=144&docHistory[]=2&

docHistory[]=20

http://eng.ege.edu.tr/~otles/ColorScience/anthocyanins.htm

www.bioquest.org/summer2008/projectfiles/leafchromatography.doc

http://facstaff.bloomu.edu/mpugh/Experiment2.pdf

http://www.ucmp.berkeley.edu/glossary/gloss3/pigments.html

Reiss, Carol 1994. Experiments in Plant Physiology. Englewood Cliffs, NJ: Prentice

Hall.

http://nationalnursingreview.com/2010/08/beta-carotene-benefits-health/

http://www.biotechlearn.org.nz/focus_stories/breeding_red_fleshed_apples/images/fruits

_high_in_anthocyanins