Optimization of Extraction Process and in Vitro Activity Study of Total Sterols from Wild Pyracantha fortuneana Leaves in Yunnan

The objective of this study was to optimize the extraction process of total sterols from wild Pyracantha fortuneana leaves (WPFL), and explore their antioxidant and whitening activities. The yield of total sterols (WPFLTPS) was used as indicator, and the single factor experiment was used to investigate the effects of extraction solvent, solid-liquid ratio, ultrasonic temperature and ultrasonic time on the yield of WPFLTPS. Based on this, the orthogonal experimental design was used to optimize the extraction conditions. The DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and nitrite methods were used to evaluate the antioxidant activity of WPFLTPS in vitro. The whitening activity was evaluated by the inhibitory effect on tyrosinase. The results showed that for optimal extraction process of WPFLTPS, the extraction solvent was absolute ethanol, ultrasonic temperature was 50 ℃, solid-liquid ratio was 1:16 g/mL, and ultrasonic time was 25 minutes. Under these conditions, the yield of WPFLTPS was (11.00±0.03) mg/g. In the range of 0.5~5 mg/mL, WPFLTPS had strong scavenging effects on DPPH radicals, ABTS⁺ radicals and nitrite ions, as well as a strong inhibitory effect on tyrosinase, demonstrating a good dose-response relationship. This extraction process was stable and reliable for extracting WPFLTPS. The WPFLTPS can be used as a new, natural antioxidant and tyrosinase inhibitor in functional foods.