Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/1998
Publication Date: N/A
Interpretive Summary: Compounds that give particular colors to seedcoats of common bean (Phaseolus vulgaris L.) Are important in that they may cause beans to become hard to cook and increasingly indigestible with time. Manteca market class beans are grown in South America and have been renowned for their flavor and ease of digestibility. An experiment was conducted to determine which compounds were found in this Manteca class and what implications these might have on digestibility. Two compounds known as flavonoids were isolated and identified from these beans. Neither of these compounds by their nature could have much effect on the overall digestibility. Other types of flavonoids known as tannins, which are known to reduce bean digestibility, were not found. Ease of digestion in Manteca beans because of a lack of tannins and the presence of specific flavonoids can lead to improved health and well-being of consumers. Humans absorb more nutrients from beans that are easy to digest compared to less digestible ones. Growing Manteca beans provides farmers with a unique opportunity to produce a new type of bean that may command a premium price in the market place.
Technical Abstract: The two flavonoid constituents from the seedcoat of Manteca-type dry bean, 'Prim' (Phaseolus vulgaris L.), of know color genotype were isolated and identified as the flavonol glycosides: 1) kaempferol-3-0-beta-D-glucoside and 2) kaempferol-3-0-beta-D-glucopyranoside-(2-1)-0-beta-D-xylopyranoside. Concentrations of these compounds as determined by HPLC analysis were: 3.6+/-0.3 and 8.5+/-0.5 mg/g dry weight of seedcoat respectively for each of the above compounds. This is the first identification of the color compounds from a dry bean genotype in which the complete color genotype is known. This demonstrates that the dominant color genes P, C, D, G are necessary to produce the two flavonol glycosides which give the seedcoats its characteristic pale yellow color. While the function of the G locus is still not known, this study indicates that g cannot be responsible for producing a 3, 5 flavonol diglycoside, but may control the addition of a second sugar, xylose, to the glucose at 3-OH. No proanthocyanins (condense tannins), which are known to reduce bean digestibility, were found in 'Prim' and this may account for its reported ease of digestibility.