Stabilities of Daidzin, Glycitin, Genistin, and Generation of Derivatives during Heating

Abstract

The soy isoflavones daidzin, glycitin, and genistin were purified from defatted soy flour using preparative-scale reverse-phase HPLC. The stabilities of the three isoflavones at different heating temperatures were investigated. Daidzin, glycitin, and genistin were lost at a rate of 26, 27, and 27% of their original concentration, respectively, after 3 min at 185 degrees C. At 215 degrees C, decreases of daidzin, glycitin, and genistin were 65, 98, and 74% after 3 min and 91, 99, and 94% after 15 min, respectively. The order of the thermal stabilities, from lowest to highest, was glycitin, genistin, and daidzin. Acetyl daidzin and acetyl genistin, daidzein, glycitein, and genistein were produced during heating at temperatures above 135 degrees C. The rate of binding of an acetyl group to form acetyl daidzin and acetyl genistin from daidzin and genistin was higher than the rate of loss of a glucoside group to form daidzein and genistein. However, acetyl daidzin and acetyl genistin decreased sharply at temperatures above 200 degrees C, while daidzein, glycitein, and genistein were relatively stable over 30 min. The stability of daidzein was higher than that of glycitein or genistein.

Additional Quantitative Trait Loci and Candidate Genes for Seed Isoflavone Content in Soybean

“…To the defatted flour samples 8 mL of methanol was added and the mixtures were then centrifuged at 1,000 g for 20 min and incubated overnight under a fume hood. The supernatant was then placed under nitrogen flow, when the solvent reached to a final volume of 2 mL, the evaporation method was stopped (Xu & Godber, 2002). For quantification of isoflavones using HPLC, 200 µl of the samples were diluted with 200 µL of mobile phase diluent which separated the liquid into two layers.…”

Isoflavone Content and Anti-acetylcholinesterase Activity in Commercial Douchi (a Traditional Chinese Salt-fermented Soybean Food)

“…Processing techniques, such as soaking, heat treatment and fermentation, not only influenced the content of isoflavones but also changed the forms of isoflavones 7,31,33 . During soaking, the concentration of daidzin-genistin decreases accordingly to the daidzein-genistein formation 24,32 .…”

Phytoestrogens in foods on the Nordic market

“…A strong temperature-dependent decrease in daidzin suggests possible thermal degradation of daidzein in addition to losses due to leaching (Grün et al, 2001). Xu et al (2002) reported the order of thermal stabilities of the purified isoflavone glucosides, from lowest to highest, as glycitin, genistin, and daidzin.…”