Isoflavone Concentrations and Composition of Soybean Varieties Grown in Upland and Lowland Regions of Vietnam

Health beneficial properties of soybean [Glycine max (L.) Merr.] isoflavones are well known. The objectives of this study were to determine and compare the isoflavone composition and concentrations of soybean varieties grown in different cultivated regions of Vietnam (i.e., upland and lowland). Total and individual isoflavone composition and concentrations were determined by high-performance liquid chromatography (HPLC). Total isoflavone concentrations varied from 1153 to $6604{\mu}g\;g^{-1}$ and averaging $3354{\mu}g\;g^{-1}$ across environments and varieties. In the lowland region, the highest total isoflavones concentration was observed in M103 cultivar ($5653{\mu}g\;g^{-1}$) and the lowest in VX9-3 ($1153{\mu}g\;g^{-1}$), whereas in the upland region the highest and lowest concentrations were in M103 ($6604{\mu}g\;g^{-1}$) and DT93 ($1938{\mu}g\;g^{-1}$), respectively. Across varieties, average total isoflavones concentration was higher in the upland than lowland region (3728 vs. $2980{\mu}g\;g^{-1}$). The malonylglucosides and acetylglucosides concentrations in upland soybean varieties were higher than those from the lowland region. Despite the presence of Genotype (G) x Environment (E) interactions, varieties with consistently high (M103) and low (VX9-3, DT93) isoflavone concentrations across environments were identified. This is the first report of isoflavones in Vietnamese soybean varieties, revealing large variation in isoflavones concentration and profile among different varieties and cultivated regions. Results will be useful in selecting high-isoflavones soybean varieties for growth in tropical regions.