Metabolite profiling of isoflavones and anthocyanins in black soybean [Glycine max (L.) Merr.] seeds by HPLC-MS and geographical differentiation analysis in Southwest China

Metabolite profiling of isoflavones and anthocyanins in black soybean seeds (BSSs) collected from different geographical locations in Southwest China was performed. A more rapid and convenient method was established to identify and quantify twelve isoflavones and eight anthocyanins in BSSs by HPLC-MS analyses. The results indicated that beta-glucoside (G-type) and malonylglucoside (M-type) derivatives, cyanidin-3-glucoside (CYL) and peonidin-3-glucoside (PEO) are the major compounds found predominantly in the isoflavones and anthocyanins of BSSs. Combined with geographical data and orthogonal partial least-squares discriminant analysis (OPLS-DA), it was demonstrated that higher isoflavone contents were found in the samples grown in the high-longitude areas of Guizhou and Chongqing, while higher anthocyanin contents were found in the samples grown in the high-latitude areas of Chongqing and Sichuan. Geographical location affected the accumulation of secondary metabolites involved in the phenylpropane pathway, especially in the trade-off/balance between isoflavone and anthocyanin biosynthesis in BSSs. Overall, a high-latitude environment has beneficial effects on the metabolism of the phenylpropane pathway, and a high-longitude environment can promote isoflavone biosynthesis, while a low-longitude environment is favorable for anthocyanin biosynthesis in BSSs.