Changes occurring in compositional components of black soybeans maintained at room temperature for different storage periods

► Isoflavones and anthocyanins in black soybeans were elucidated by HPLC-DAD-ESI/MS. ► Isoflavones and anthocyanins in black soybeans decreased markedly during storage. ► Genistein and cyanidin-3-O-glucoside showed the greatest decrease during storage. ► Antioxidant activities of black soybeans decreased during storage. ► The contents of protein, oil, and fatty acid showed a slight decrease during storage.