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Antioxidant activities of Syzygium polyanthum Wight leaves extracts (methanol, ethyl acetate, dichloromethane, and hexane) were evaluated by using DPPH (2,2-diphenyl-2-picrylhydrazyl hydrate) and ABTS (2,2’-azinobis (3-ethylbenzothiazole-6-sulfonic acid) methods. The methanol extract showed the highest antioxidant activity of DPPH assay among extracts with IC50 value of 55.2 mg/ml. In addition, methanol extract also showed the highest antioxidant activity of ABTS assay among extracts with IC50 value of 17.41 mg/ml. It indicated that methanol extract of S. polyanthum Wight leaves potential for antioxidant.

Moringa oleifera have been evaluated for its antioxidant activity. M. oleifera leaves were extracted with methanol, ethyl acetate, dichloromethane and n-hexane. The antioxidant activity of extracts were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity assay and an improved 2,2’-azino-bis-[3-ethylbenzothiazoline sulphonate] (ABTS) radical cation decolorization assay in vitro. Trolox was used as standard with IC50 5.89 μg/mL in DPPH assay and 3.06 μg/mL in ABTS assay. The methanol extract showed the highest free radical scavenging activity with IC50 value of 49.30 μg/mL in DPPH assay and 11.73 μg/mL in ABTS assay. This study provided that M. oleifera leaves possess antioxidant.

New Prenylated stilbene derivatives, 3-hydroxy-4-prenyl-5-methoxy-stilbene acid (1) and 5,4'-dihydroxy-3-methoxy-2-prenyl-stilbene (2) had been isolated from methanol extract of Cajanus cajan (L.) Millsp. (Pigeon pea), a member of family fabaceae. The aim of this present work was to evaluate its in vitro antioxidant activity using 2,2-diphenyl-1-picryhydrazyl (DPPH) radical-scavenging. Isolation of compounds was achieved by extraction (maceration) and chromatographic technique. The structures of the compounds were determined based on UV, IR, 1H-NMR and 13C-NMR spectra and also by comparing with the previously reported data. Antioxidant activities (IC50) of 1 and 2 were 413.68 μg/mL and 271.53 μg/mL, respectively.