Purpose To optimize the extraction process conditions for total flavonoids from Toona sinensis, and to evaluate the effects of different varieties and harvesting periods on the total flavonoid content and antioxidant activity of T. sinensis.
Methods Using old leaves of Yunnan T. sinensis as material, total flavonoids were extracted using ultrasonic-assisted ethanol method, and the extraction conditions were optimized through single-factor experiments and response surface methodology. Using the optimized method, the total flavonoid content of Yunnan T. sinensis and Jiangcheng T. sinensis in Jan., Mar., May, Jul., and Sep. was extracted and determined. Their antioxidant activities were evaluated based on their abilities to scavenge DPPH free radicals and ABTS+ free radicals.
Results The optimal extraction conditions for total flavonoids in T. sinensis leaves were as follows: volume fraction of ethanol was 63%, solid-to-liquid ratio (g∶mL) was 1∶37, extraction temperature was 52 ℃, and extraction time was 62 min. For T. sinensis petioles, the best extraction conditions were as follows: volume fraction of ethanol was 58%, solid-to-liquid ratio (g∶mL) was 1∶24, extraction temperature was 40 ℃, and extraction time was 61 min. From Jan. to Sep., the total flavonoid content in Yunnan T. sinensis first increased and then decreased, while that in Jiangcheng T. sinensis showed fluctuating changes, and the total flavonoid content of both varieties reached its peak in May. The total flavonoid content of T. sinensis was significantly positively correlated with DPPH radical scavenging rate and ABTS+ radical scavenging rate (P<0.01).
Conclusion The optimized extraction conditions in this study have improved the yield of total flavonoids from T. sinensis. The total flavonoids content of T. sinensis harvested in spring is relatively high, and the substance exhibits strong antioxidant activity.
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