Soy isoflavone analysis: quality control and a new internal standard

Abstract

Development of a database of the soy isoflavone content of foods requires accurate and precise evaluation of different food matrixes. To evaluate accuracy, we estimated recoveries of both internal and external standards in 5 different soyfoods weekly. Standards were evaluated daily for system quality assurance. To evaluate sample precision, we analyzed soybeans and soymilk bimonthly for within-day precision and over 4 d for day-to-day precision. CVs should be < or = 8%. We validated our methods for single and multiple recovery concentrations by using our new internal standard, 2,4,4'-trihydroxydeoxybenzoin, and the external standards daidzein, genistein, and genistin. Concentrations of 12 isoflavone isomers, 3 aglycones (daidzein, genistein, and glycitein), and 9 glucosides (daidzin, genistin, glycitin, acetyldaidzin, acetylgenistin, acetylglycitin, malonyldaidzin, malonylgenistin, and malonylglycitin) were measured in a variety of soybeans and soyfoods. The extraction methods used depended on soyfood type. The HPLC conditions for soy isoflavone analysis were improved, leading to good separation with a short analysis time (60 min/sample). A data bank of concentration and distribution of isoflavones in different soybean products was assembled. A wide range of isoflavone concentrations, from < 50 microg/g to > 20,000 microg/g, was found in different soy products. The glucoside forms are almost twice the molecular weight of the aglycones; reported isoflavone concentrations should be normalized to the aglycone mass (or an isoflavonoid equivalent) rather than a simple sum of all isomers.

Isoflavonas em produtos comerciais de soja

“…Segundo SONG et al [20], o teor de isoflavonas na maioria dos alimentos à base de soja varia de 100 a 300mg/100g.…”

Greater Apparent Absorption of Flavonoids Is Associated with Lesser Human Fecal Flavonoid Disappearance Rates

“…Apigenin, naringenin, kaempferol, luteolin, quercetin, flavone, chrysin, 7,4 0 -dihydroxyflavone, 6,4 0 -dihydroxyflavone, 5,4 0 -dihydroxyflavone, and 5,3 0 -dihydroxyflavone were from Indofine Chemical Co., Inc. (Hillsborough, NJ). Daidzein and 2,4,4 0 -trihydroxydeoxybenzoin (THB) were synthesized using the method of Song et al (17). Genistein was synthesized according to a modification of the method of Chang et al (18).…”

Resíduos de glifosato e ácido aminometilfosfônico e teores de isoflavonas em soja BRS 244 RR e BRS 154

“…A separação das isoflavonas foi realizada em coluna C 18 Nova-pak® 4 µm (Waters, Milford, EUA) de acordo com o método proposto por Song et al (1998 Os resultados foram expressos como mg de isoflavona por 100 g de amostra (b.u. ), após normalização das diferenças de peso molecular das amostras glicosiladas, feita multiplicando-se a massa de cada derivado pela razão entre o peso molecular da respectiva aglicona e o peso molecular da forma glicosilada, conforme Song et al (1998).…”

“…), após normalização das diferenças de peso molecular das amostras glicosiladas, feita multiplicando-se a massa de cada derivado pela razão entre o peso molecular da respectiva aglicona e o peso molecular da forma glicosilada, conforme Song et al (1998).…”