Isoflavone profile and antioxidant activity of Brazilian soybean varieties. Food Science and Technology International

Thirteen varieties and one new strain of soybean, developed by the Genetic Improvement Program from Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), crop year of 2003, were analysed in rela-tion to their isoflavones profiles and contents. Total isoflavone content varied from 57 to 188mg per 100g of soybeans. Most (90–95%) of the isoflavones were present as glycosilated derivatives. The -gly-cosides represented the main forms of the isoflavones in the seed (50 to 59 % of the total) followed by malonylglycosides (28 to 39 % of the total). The ratio between malonyldaidzin and daidzin varied from 0.44 (Embrapa soyseeds BRS 155) to 0.74 (BRS 185) and between malonylgenistin and genistin from 0.56 (BRS 155) to 0.87 (BRS 185). The total percentage of each isoflavone, corresponding to the sum of the four chemical forms (malonylglycoside, acetylglycoside, -glycoside and aglycone) varied from 39 to 57 % for genistein, 34 to 47 % for daidzein, and 8 to 17 % of the total for glycitein. Antioxidant activity varied from 37.8 (BRS 214) to 48.9 % (BRS 233) of inhibition of the -carotene bleaching, and a low cor-relation was found for antioxidant activity and total phenolics content or level and kind of isoflavones. Key Words: soybean, isoflavones, antioxidant activity, -carotene-bleachin