In this work, optimization of ultrasound-assisted extraction (UAE) of Osmanthus fragrans (OF) fruit oils from four representative species of OF groups was firstly performed. A Box-Behnken design was applied to investigate and optimize the process variables. Among them, the specie of OF var. latifolius Makino (OFL) had the highest oil yield (18.53 %) by UAE under the optimal conditions with an ultrasound extraction time of 33 min, ultrasound temperature of 52 ℃ and liquid-to-solid ratio of 12 mL/g. Furthermore, the fatty acid composition, physicochemical characteristics, and antioxidant activity of OFL fruit oil extracts obtained through UAE and Soxhelet extraction (SE) were determined and compared. The results demonstrated that the oil yield and fatty acid composition between UAE and SE were similar, while the oil obtained by UAE displayed superior physicochemical properties and antioxidant activity . These findings suggest that UAE represents an effective method for OF fruit oil extraction.
Torreya grandis Fort. ex Lindl. is a plant belonging to the Taxaceae family and Torreya grandis cv. Merrillii is the only grafted and thoroughbred species belonging to this species. In this study, we extracted five different seed oils, including T. grandis seed oil (TGSO), T. grandis “Xiangyafei” seed oil (XYSO), T. grandis “Zhimafei” seed oil (ZMSO), T. grandis “Majus”seed oil (TGMSO), and T. grandis “cunguangfei” seed oil (CGSO) using physical pressure. The resulting extracts were analyzed to determine their fatty acid composition, antioxidant activity, and inhibitory activity towards tyrosinase. The results of the antioxidant activity assays revealed that XYSO and ZMSO exhibited much greater DPPH radical scavenging activity and ferric reducing power than TGSO. Notably, all five of the seed oils showed dose-dependent inhibitory activity towards tyrosinase. XYSO and TGSO gave the highest activities of all of the seed oils tested in the current study against monophenolase and diphenolase, with IC 50 values of 227.0 and 817.5 μ g/mL, respectively. The results of this study show that wild TGSOs exhibit strong antioxidant and tyrosinase inhibition activities. These results therefore suggest that wild TGSOs could be used as a potential source of natural antioxidant agents and tyrosinase inhibitors.