Mallotus repandus (MR) is used in Thai traditional medicine recipes for anti-inflammation and adaptive homeostasis. Bergenin is the bioactive constituent in MR stem. This study evaluated the in vitro antioxidant activity of bergenin and the methanol, ethanol, and water extracts of MR stem prepared by maceration and Soxhlet extraction by assaying 2,2-azino-bis-(3- ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS•+), hydroxyl (•OH), superoxide (•O2), and nitric oxide (NO•) radical scavenging activities and ferric reducing antioxidant power. Bergenin had the highest ferric reducing power and all the MR extracts showed concentration-dependent ferric reducing power. Methanol and water extracts showed superior radical scavenging activities compared to ethanol extract. The water and methanol Soxhlet extracts demonstrated the highest ABTS•+ and •OH radical scavenging activities, respectively, and the macerated water extract had the lowest •O2 and NO• IC50 values. Therefore, MR stem and bergenin are promising natural candidates for developing antioxidant supplements.
