Objective Extraction of polyphenols from Sarcandra glabra leaves was optimized, and antioxidant activity and anti-aging efficacy on skin of the extract evaluated.

Methods Polyphenols were extracted from the leaves by an ultrasound-assisted enzymatic process and optimized applying single-factor experiments with the Plackett–Burman design, steepest ascent experiments, and Box–Behnken response surface methodology. In vitro antioxidative and skin anti-aging effects were assessed using the free radical-scavenging assay, the skin-aging-related enzyme inhibition test, and the tert-butyl hydroperoxide (t-BHP)-induced senescence model in HaCaT.

Results The optimal polyphenol extraction used a liquid-to-solid ratio of 20∶1 (mL·g⁻¹) on the leaves and a reaction base of ethanol in volume fraction of 50% for a 40 m enzymatic digestion at 50 °C and pH 5.0 with 30 m 300 W ultrasonic application. Cellulase and tanninase at 1∶1 ratio were the enzymes applied at 4% of mass of S. glabra leaves. A polyphenol yield of （58.22±0.1） mg·g⁻¹ was achieved under the processing conditions. The secured extract scavenged DPPH and ABTS free radicals with IC₅₀ of 0.142 mg·mL⁻¹ and 0.048 mg·mL⁻¹, respectively. It significantly inhibited the skin aging-related collagenase and elastase activities. In the t-BHP-induced senescent HaCaT cell experiments, the applied concentrations of the extract ranging from 31.25 μg·mL⁻¹ to 125 μg·mL⁻¹ significantly reduced malondialdehyde (MDA) and restored superoxide dismutase (SOD) activity.

Conclusion The optimized extraction process significantly improved the yield of polyphenol from S. glabra leaves. The extract showed a significant in vitro antioxidative activity and anti-aging potential on skin.