Plant Pigments Chromatography

Transcription

1 Plant Pigments Chromatography Gary Stacey Lab Teacher workshop, March 8, 2014 University of Missouri Division of Plant Sciences

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3 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

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5 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

6 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

7 Carotenoids 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

8 Carotenoids Carotenoids and xanthophylls - tetra-terpenes - are non-polar - represent more 60 pigments

9 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

10 Anthocyanins - phenolic pigments - are polar - water soluble Anthocyanins

11 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

12 Chromatography Background Retention factor (R f ) values of pigments R f = Distance pigment traveled Distance solvent traveled = a b b a

13 Chromatography Background Rf values of pigments Carotene ; orange Pheophytin ; olive green Chlorophyll a ; blue-green Chlorophyll b ; yellow-green Anthocyanins - between 0.32 and 0.62; red, pink, purple and blue colors Xanthophyll , yellow Xanthophyll , yellow ography.doc

14 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 R f value R f 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.

15 Other applications e.g., beverages, paint, pen ink, etc.

16 References dochistory[]= Reiss, Carol Experiments in Plant Physiology. Englewood Cliffs, NJ: Prentice Hall. _high_in_anthocyanins