This study was designed to evaluate both the antioxidant and free-radical scavenging activities of extract and fractions from corn silk. N-butanol fraction (BF) demonstrated the highest total phenolic content (164.1 ± 9.7 μg GAE/g DCS) and total flavonoids content (69.4 ± 5.1 μg RE/g DCS), accompanied with the highest antioxidant activity compared to other fractions through all antioxidant assays. Two flavone glycosides showing potent antioxidant activity were isolated from BF and identified, by comparing spectral data (UV, FAB-MS and NMR) with literature values, to be isoorientin-2″-O-α-l-rhamnoside and 3′-methoxymaysin. The two isolated flavone glycosides, particularly isoorientin-2″-O-α-l-rhamnoside, demonstrated significant total antioxidant activity, DPPH radical scavenging activity, reducing power and iron-chelating capacity, with EC50 values of 14.24 ± 1.49, 22.69 ± 2.33, 6.58 ± 1.07 and 30.25 ± 3.05 μg/ml, respectively. Results obtained indicated that corn silk extracts can be used potentially as a ready accessible and valuable bioactive source of natural antioxidants.
Research highlights
► In this study, the antioxidant and free-radical scavenging activities of crude ethanol extract and fractions of corn silk were systematically evaluated for the first time. ► Two flavone glycosides were isolated and identified from n-butanol fraction from corn silk, which demonstrated highest antioxidant and free-radical scavenging activities. ► The antioxidant activities of the two isolated flavone glycosides were investigated for the first time and the result demonstrated that they were potent antioxidants. ► The results in this study may the possibility of using corn silk as source of low-cost natural antioxidant.