New isoflavone glucosides in yabumame (Amphicarpaea bracteata (L.) Fernald subsp. edgeworthii (Benth.) H.Ohashi var. japonica (Oliv.) H.Ohashi) and their effect on leukotriene B ₄ 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.

Keywords: Allergy; Isoflavone glucoside; Leukotriene B4; The Ainu people; Yabumame.