Objective The leaves of Dalbergia sissoo (Roxb.) contain polyphenols and flavonoids. Polyphenols and flavonoids are scavengers of free radicals in organisms, preventing the toxic effects of free radicals on the body and inhibiting lipid peroxidation, i.e. antioxidant activity. Therefore, understanding of polyphenols extraction form leaves and its antioxidant activity in vitro could provide theoretical basis of utilization of leaves of D. sissoo.

Method Ethanol was used as the extract of polyphenols in leaves of D. sissoo, and then single factor experiment and orthogonal experiment were used to determine the extraction process of polyphenols. At the same time, the removal capacity of DPPH-free radical of ethanol-water extract of leaves of D. sissoo was identified.

Result Low-concentration of polyphenol solution of leaves of D. sissoo had strong antioxidant activity. The concentration of polyphenol solution for inhibitory half number of DPPH free radical (IC₅₀) was about 3.2 mg·L^-1, much higher than concentration 2.5 mg·L^-1 of Vc, but its reducing ability was slightly lower than the Vc.

Conclusion Leaves of D. sissoo are rich in polyphenols and have strong antioxidant activity, which can be used as natural antioxidant plant resources for development and utilization.