Abstract: The ultrasonic extraction of polyphenols from Osmanthus fragrans fruits was optimized by one-factor-at-a-time combined with orthogonal array design method to maximize extraction efficiency. The optimal extraction conditions were found to be 70% aqueous ethanol as extraction solvent at a solid-to-liquid ratio of 1:8 (g/mL) for twice repeated extraction for 40 min each time. Under these conditions, the yield of polyphenols was 2.83 mg/g. The reducing power of the obtained extract was distinctly higher than that of vitamin C at the same concentrations. Its maximum scavenging rates against hydroxyl free radicals and nitrite ions were 96.3% and 65.4%, respectively. In addition, the extract revealed stronger antioxidant effect on lard. This study could provide references for the comprehensive exploitation of Osmanthus fragrans fruits.

Key words: Osmanthus fruit, polyphenols, ultrasonic extraction, antioxidant activity