Changes in nutritional components and antioxidant activities from soybean leaves containing high isoflavone contents according to different storage temperatures and periods

Abstract

This study investigated that change of the nutrients (including fatty acids, amino acids, and minerals) and total phenolic (TP), total flavonoid (TF), and isoflavone contents and antioxidant activities during the storage of soybean leaves containing high isoflavone contents at 5, 25, and 55oC for 180 days. The contents of free amino acids were increased from 1313.81 mg/100 g at 0 day to 1776.15, 1693.93 and 1551.18 mg/ 100 g at 5, 25, and 55oC storage for 180 days, respectively, but the values of fatty acids were little unchanged. The contents of minerals were detected from 51.65 mg/100 g (0 day) to 49.93 (5oC), 50.20 (25oC), and 61.21 (55oC) mg/100 g at 180 days, respectively. The levels of total isoflavones did not change during the storage periods. In case of storage at 55oC, the contents of glycosides (1347.78→2195.13 μg/g) and aglycones (342.79→ 480.61 μg/g) increased during storage, while the levels of malonylglycosides (2209.22→1289.48 μg/g) decreased. Also, the TP and TF contents were slightly increased from 9.31 and 8.61 mg/g at 0 day to 9.97 and 9.3 mg/g at 180 days, corresponding to the radical scavenging activities of 2,2-diphenyl-1-picrydrazyl, 2,4,6-azino-bis (3-ethylbenzthiazoline-6-sulphnoic acid), and hydroxyl increased from 30.91, 55.98 and 23.27% from 37.10, 62.54, and 30.95%, respectively. ? The Korean Society for Applied Biological Chemistry 2020.