Comparative investigation on variations of nutritional components in whole seeds and seed coats of Korean black soybeans for different crop years and screening of their antioxidant and anti-aging properties

This research was conducted to demonstrate the comparisons of nutritional constituents (isoflavone; anthocyanin; protein; fatty acid; oil) and biological properties (antioxidant, anti-aging) in whole seeds and seed coats of black soybeans for crop years. Isoflavones and anthocyanins showed considerable differences in cultivars and growth years with the ranges of 794.9–4195.3 μg/g and 2.3–14.4 mg/g, while other components exhibited slight variations. In particular, malonylgenistin and cyanidin-3-O-glucoside were observed the most abundant phenolics, comprising approximately 35.5 (778.0 μg/g) and 76.7% (4.6 mg/g) of total average contents (isoflavone: 2197.8 μg/g; anthocyanin: 6.0 mg/g). Moreover, the whole seeds and seed coats displayed excellent activities in antioxidant (radical; DNA protectant), tyrosinase inhibition, and elastase inhibition. Their effects significantly occurred with dose-dependent patterns as follows: elastase (150 μg/mL) > tyrosinase (600 μg/mL) > ABTS (1500 μg/mL) > DPPH (1500 μg/mL) with higher abilities of seed coats than whole seeds. The DNA protection exhibited higher rates in seed coats with > 90% at 200 μg/mL. Natably, Socheong (isoflavone; 4182.4 μg/g) and Geomjeong 2 (anthocyanin: 10.3 mg/g) cultivars may be recommended as potential sources to the development of functional agents and new cultivars owing to their high average phenolic contents.