Analysis of Isoflavone, Phenolic, Soyasapogenol, and Tocopherol Compounds in Soybean [Glycine max (L.) Merrill] Germplasms of Different Seed Weights and Origins

This study investigated the functional compounds, including isoflavones, phenolics, soyasapogenols, and tocopherols, that were detected in 204 soybean [Glycine max (L.) Merrill] germplasms. The soybean samples were divided into three groups according to origin: America, China, and Korea. The soybean samples were also classified into three groups on the basis of 100-seed weight: small (<13 g), medium (13–24 g), and large (>24 g). Among the soybean germplasms, CSRV121 (Bosukkong) had the highest level of isoflavone content (4778.1 μg g–¹), whereas CS01316 had the lowest isoflavone content (682.4 μg g–¹). Of the soybeans from the three different countries of origin, those from Korea showed the highest average concentration of total isoflavones (2252.6 μg g–¹). The small seeds had the highest average total isoflavone concentration (2520.0 μg g–¹) of the three different seed sizes. Among the 204 soybean germplasms, CS01405 had the highest content of total phenolics (5219.6 μg g–¹), and CSRV017 (Hwangkeumkong) had the lowest phenolic content (654.6 μg g–¹). The mean concentrations of total phenolic compounds were 2729.1 μg g–¹ in American soybean seeds, 1680.4 μg g–¹ in Chinese soybean seeds, and 1977.6 μg g–¹ in Korean soybean seeds. Of the soybean seeds from the three different countries of origin, American soybean seeds had the highest average concentration of total phenolic compounds, and Korean varieties showed the second highest value. Small soybean seeds had the highest average content of total phenolic compounds (2241.7 μg g–¹), whereas medium-sized (1926.8 μg g–¹) and large (1949.9 μg g–¹) soybeans had lower concentrations of phenolic compounds. In whole soybean germplasms, the level of total soyasapogenols was higher in CS01173 (1802.3 μg g–¹) and CS01346 (1736.8 μg g–¹) than in the other types of soybeans. The mean concentrations of total soyasapogenol were 1234.0 μg g–¹ in American, 1294.5 μg g–¹ in Chinese, and 1241.5 μg g–¹ in Korean soybean varieties. Chinese soybean varieties showed the highest mean concentration of total soyasapogenol, and Korean soybean seeds showed the second highest level. The medium-seed group had the highest soyasapogenol content (1269.3 μg g–¹) of the seeds that were grouped by size. A larger amount of soyasapogenol B than soyasapogenol A was detected. In whole soybeans, CS01202 showed the highest level of total tocopherols (330.5 μg g–¹), whereas CSRV056 (Pungsannamulkong) had the lowest content (153.3 μg g–¹). Chinese soybeans had the highest average concentration of total tocopherols (255.1 μg g–¹). By comparison, the medium-sized Chinese soybean group had the highest (256.1 μg g–¹) average total tocopherol content.