New isoflavone glucosides in yabumame (Amphicarpaea bracteata (L.) Fernald subsp. edgeworthii (Benth.) H.Ohashi var. japonica (Oliv.) H.Ohashi) and their effect on leukotriene B4 production in mast cells.

Yabumame (Amphicarpaea bracteata (L.) Fernald subsp. edgeworthii (Benth.) H.Ohashi var. japonica (Oliv.) H.Ohashi) is a legume plant that the Ainu people eat as a traditional food, although the bioactive ingredients other than vitamins have not been studied. In this study, the structures of yabumame isoflavone glucosides were determined and their effect on leukotriene (LT) B4, a chemical mediator of type I allergy, produced in mast cells, was investigated in vitro. Seven compounds were isolated from yabumame. Their structures were determined by spectroscopic and spectrometric analyses, which were genistein-7-O-β-d-glucoside (1), formononetin-7-O-(2″-O-β-d-glucosyl)-β-d-glucoside (2), formononetin-7-O-β-d-glucoside (3), biochanin A-7-O-(2″-O-β-d-glucosyl)-β-d-glucoside (4), formononetin-7-O-(6″-O-malonyl)-β-d-glucoside (5), biochanin A-7-O-(2″-O-β-d-glucosyl-6″-O-β-d-glucosyl)-β-d-glucoside (6), and biochanin A-7-O-(6″-O-malonyl)-β-d-glucoside (7). Compounds 2, 4, and 6 were determined as new compounds. Compound 3 showed statistically significant suppressive effect on LTB4 production in mast cells, although the activity was not strong. On the other hand, biochanin A, an aglycone common to compounds 4, 6, and 7, strongly inhibited the LTB4 production. The results suggest that some of yabumame isoflavone glucosides might contribute to mitigate type I allergy. Seven isoflavone glucosides including 3 new compounds were found in yabumame and their anti-allergic effect was evaluated.