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