Rhus semialata Murr. var. roxburghiana DC. stem (RSRS) is a Taiwanese native folk medicine for anti-inflammation and the treatment of diarrhea and liver disease. Five extracts and a main constituent, gallic acid, elucidated inhibitory effects on ferrous ion-induced lipid peroxidation (LPO) in mice liver mitochondria (IC50: 10.8 ± 0.7-55.2 ± 0.6 and gallic acid: 36.1 ± 3.1 μg/mL). None of the samples tested induced LPO production. The IC50 values for antioxidant activities were 1) 1,1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging: 1.5 ± 0.08-56.2 ± 1.1 μg/mL; 2) superoxide anion radical scavenging: 53.5 ± 0.7-226.6 ± 2.1 μg/mL; 3) hydrogen peroxide scavenging: ethyl acetate (EA) and acetone extracts 264.2 ± 4.7 and 208.0 ± 1.9 μg/mL, respectively; and 4) ferric-reducing antioxidant power (FRAP): EA extract, equivalent Trolox 116.4 ± 0.3 μM. The total phenolic content of the extracts was 82.0 ± 2.1-455.2 ±9.3 μg gallic acid equivalents/mg. The highest flavonoid and flavanol contents of the extracts were acetone extract 30.9 ± 2.7 μg rutin equivalents/mg and water extract 10.9 ± 0.05 μg epicatechin equivalents/mg. Next, the gallic acid content of each extract was quantitatively analyzed using high-performance liquid chromatography (HPLC), which showed one main peak. Based on this evidence, RSRS and gallic acid may be used as a potential antioxidant and LPO inhibitor for developing a natural liver-protective phytochemical.
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