Comparative analysis of isoflavone aglycones using microwave-assisted acid hydrolysis from soybean organs at different growth times and screening for their digestive enzyme inhibition and antioxidant properties

Abstract

The objectives of this research were to demonstrate the changes in isoflavone-aglycones, total phenolics, and biological properties (digestive enzyme inhibition; antioxidant) from six organs including leaves, leafstalks, roots, stems, seeds, and pods at different growth times of soybean plant. Three isoflavone-aglycones in microwave-assisted acid hydrolysis extracts were elucidated using UHPLC-ESI-Q-TOF-MS/MS and their contents exhibited remarkable differences in leaves (245.93-2239.33 mu g/g), roots (854.96-4425.34 mu g/g), and seeds (ND-2339.62 mu g/g). Specifically, the collected samples on 15-Oct (leaves: 2239.33; seeds: 2339.62 mu g/g) and 31-Aug (roots: 4425.34 mu g/g) showed the highest isoflavone-aglycones, and daidzein was observed the most abundant component, comprising approximately 70%. Moreover, the inhibitions against alpha-glucosidase and alpha-amylase displayed the predominant effects in roots (89;91%) and leaves (81;85%) of samples on 31-Aug and 15-Oct at 300 mu g/ml. The antioxidant activities on ABTS, DPPH, and hydroxyl radicals increased considerably with the increases of growth times in leaves and seeds, especially, ABTS showed the highest scavenging abilities: leaves (15-Oct;83%) > roots (31-Aug;75%) > seeds (15-Oct;68%). Therefore, our results suggest that soybean leaves, roots and seeds may be considered as excellent natural sources for nutraceuticals.