Distribution of Leaf Flavonoid Aglycones and Glucuronides in the Genus Phaseolus and Related Genera

Abstract

Ninety-six species and hybrids of the genus Phaseolus and related genera, Dysolobium, Macroptilium, Strophostyles, and Vigna are surveyed for their leaf flavonoid (flavone/flavonol) aglycone and glucuronide distribution patterns. The aim is to determine whether the distribution patterns of certain flavonoid aglycones and/or glucuronides are restricted in each genus and hence, could be used to delineate the genus. The results show that flavonol aglycones (kaempferol and quercetin) are more frequent in the entire group than the flavones (luteolin and apigenin). Kaempferol is more prevalent than quercetin in the genus Macroptilium, while Strophostyles accumulates mainly quercetin. There is generally no restricted pattern for a particular type of flavonoid aglycone in Phaseolus and Vigna genera. Results also show the presence of flavonoid glucuronides in six out of 18 species of Phaseolus surveyed, but are absent in all the species of Vigna, Macroptilium, and Strophostyles. The situation in Dysolobium is inconclusive. A flavonoid band moved toward the anode during electrophoresis (a positive test for the presence of glucuronide) but glucuronic acid was not detected during subsequent analysis. In the genus Phaseolus, all the species and cultivars that accumulate flavones such as P. coccineus, P. ricciardianus and P. parviflorus accumulate flavone glucuronides, while P. vulgaris, P. tuberosus and P. zebra accumulate flavonol glucuronides.