Structural characterization and antioxidant and anti-inflammatory activities of new chemical constituent from the seeds of bambara groundnut (Vigna subterranea (L.) Verdc.)

A new compound (C20H18O9) was isolated from bambara groundnut seeds (Vigna subterranea (L.) Verdc.) and identified as a luteolin glycoside based on 1H, 13C and 2D nuclear magnetic resonance spectroscopy data and previously reported data. This compound exhibited similar scavenging activity for DPPH radical to Trolox and had a higher inhibitory effect on superoxide anion radicals than gallic acid and Trolox. C20H18O9 exhibited an inhibitory effect on DPPH and superoxide anion radicals, with IC50 values of 2.25 ± 0.14 µg/mL and 9.8 ± 0.3 µg/mL, respectively. However, C20H18O9 displayed low activities for FRAP and metal chelation. C20H18O9 had a higher inhibitory effect on lipoxygenase (IC50 = 2.16 ± 0.14 µg/mL) than nordihydroguaiaretic acid but had a lower inhibitory effect on xanthine oxidase than allopurinol. These results indicate that bambara groundnut seeds can be natural sources of antioxidants for humans and can serve as lipoxygenase inhibitor to reduce inflammation.