Antioxidant Activity, α-glucosidase Inhibitory Activity and Chemoprotective Properties of Rhododendron brachycarpum Leaves Extracts

Background: Rhododendron brachycarpum (RB) is a genus of flowering plants generally used for traditional medicine in Korea to treat hypertension, neuralgia, and sterility. Previous studies have shown that RB extract alleviate inflammation and antimicrobial activity. Objective: In this study, the effects of RB and its different fractions (n-hexane, ethyl-acetate and n-butanol) on antioxidant activity, DNA damage prevention and the activity of α-glucosidase were studied. Results: The antioxidant ability of RB was investigated in vitro, including that of DPPH-radical and reducing power. As expected, scavenging effect against DPPH-radical of ethyl acetate fraction (IC50 = 17.7 ± 0.5 μg/ml) of RB had the highest DPPH radical scavenging activity, and it was superior to the positive control, butylated hydroxytoluene (BHT) (IC50 = 80.8 ± 1.5 μg/ml). And the reducing power of RB was 3.18 at 1.0 mg/ml. Meanwhile, the α-glucosidase inhibitory activity and prevention of oxidation stress-induced DNA damage were also highest in the ethyl acetate fraction. Pretreatment of pancreatic β-cells from Syrian golden hamster (HIT-TI5) with the ethyl acetate fraction at concentrations of 300 μg/ml significantly protected the cells from high glucose-induced cell death. Conclusion: Our results indicate that ethyl acetate fraction of RB leaves extract has strong antioxidant, α-glucosidase, and prevention of DNA damage activities, and furthermore, ethyl acetate fraction significantly protected the cells from high glucose-induced cell death.