Phenolic acids and flavonoids in soybean root and leaf extracts

Abstract

An HPLC technique and a GC-MS method were used to analyze extracts from soybean leaves and roots for phenolic acids and flavonoids. The reverse-phase HPLC technique involved comparing relative retention times and wavelength area ratios of standard compounds to unknown compounds in the soybean extracts. In addition, the standard compounds and extracts were derivatized with a silylation reagent, yielding trimethylsilyl (TMS) derivatives, and analyzed by GC-MS. The HPLC and GC-MS analyses of the hydrolyzed soybean root extract revealed the presence of 4-hydroxybenzoic, vanillic, ferulic, gentisic, syringic and protocatechuic acids, genistein, daidzein and coumestrol. Results from the HPLC analysis of the hydrolyzed leaf extract indicate the presence of salicylic, 4-hydroxybenzoic, vanillic, 4-hydroxycinnamic, ferulic, caffeic, gentisic, and syringic acids, naringenin, quercetin, genistein, and daidzein. GC-MS analysis of the leaf extract confirmed the presence of all of these compounds except salicylic acid. In addition, the GC-MS analysis of the leaf extract also indicated the presence of kaempferol.