Abstract: Objective: To explore the antioxidant activities of different solvent extracts from Syringa pubescens Turcz bark. Methods: ABTS+ · and DPPH free radical scavenging and ferric reducing assay were used for antioxidant activity evaluation. The content of total phenols in 75% ethanol extract and its different solvent fractions (ethyl acetate, n- butanol and petroleum ether) were determined spectrometrically. Results: All the investigated samples had strong ability to scavenge DPPH free radicals and reduce ferric ions in a dose-dependent fashion. Among them, the strongest antioxidant activity was observed in n- butanol fraction. The maximum scavenging rate of n-butanol fraction against ABTS+ · was 96.28% at the concentration of 0.62 mg/mL. However, its maximum scavenging rate of against DPPH radicals was 96.16%, which was close to that of vitamin C. The IC50 of the fraction against ABTS+ · and DPPH radicals were 0.074 mg/mL and 0.012 mg/mL, respectively. In addition, it had the strongest antioxidant activity, which might be largely associated with its high level of total phenols, 120.1μg/20 mg. Conclusion: Syringa pubescens Turcz bark has good antioxidant capacity, in which components soluble in both 75% ethanol and n-butanol reveal the strongest antioxidant capacity.

Key words: Syringa pubescens Turcz, antioxidant, total phenols, correlation