Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Proceedings
Publication Acceptance Date: 3/31/1998
Publication Date: N/A
Interpretive Summary: Flavonoids are compounds that give particular colors to seedcoats of common bean (Phaseolus vulgaris L.) and are important in that they also are potent antioxidants that protect the body from cancer causing agents. However, some flavonoids can also cause beans to darken in color on aging, become hard to cook and increasingly indigestible. An experiment was conducted to determine which compounds particular seedcoat color genes code for. By using a technique called chromatography which allows for the separation of compounds based on their solubility in different liquid media, we were able to determine the effect of the "G" gene for seedcoat color. When the "G" locus is in the recessive form i.e., "g", seed coats contain much less of a particular flavonoid than when in the dominant i.e. "G" form. Hence, "G" probably controls the amount of flavonoid present rather than the presence or absence of the flavonoid. We are now determining how potent are the antioxidant activities of the "G gene flavonoids. Knowing which genes give bean seedcoats their color is important to breeders because they now can more easily breed for particular colors that define the various market classes. The new data from our work is important to farmers because they may be able to market beans with particular antioxidants and ease of digestibility more easily than beans without these qualities. Pharmaceutical companies may also benefit from our work because of the potential to extract particular flavonoids from bean seedcoats and market them as nutritionally important food supplements.
Technical Abstract: Two dry bean (Phaseolus vulgaris L.) varieties of known genotype for seedcoat color were extracted and analyzed. The yellow brown seedcoat genotype (P , C, D, J, G, b, v) and green brown genotype (P, C, D, J, g, b, v) differ from each other by only a single recessive substitution at the G locus. Enough material was available from yellow brown to extract, isolate and identify kaempferol-3-O-beta-D-glucoside (astragalin). Small amounts of extract from the yellow, brown and green brown genotype were analyzed using thin layer chromatography (TLC), high pressure liquid chromatography (HPLC), and ultraviolet (UV) scans. Co-chromatography of astragalin, yellow brown and green brown methanol extracts indicated the presence of astragalin in the yellow brown genotype, but not in the green brown genotype. However, when green brown methanol extract was analyzed by HPLC there was a peak with the same retention time as astragalin, and when co-injected with astragalin the peak area increased. When pure astragalin was scanned under UV, there were two absorption peaks at 270 and 360 nm, and yellow brown extract also showed these two peaks, but green brown extract did not. The above results suggest that either a similar compound to astragalin is present in green brown extract, or astralagin is present at low concentrations. The likely role of G is either to permit the formation of flavonols or to promote the production of flavonols.