Optimization of extraction process by response surface methodology and antioxidant activity analysis of triterpenic acid from Lycopus lucidus Turcz

【Objective】To optimize extraction process of triterpenic acid from Lycopus lucidus Turcz and analyze its antioxidant activity，so as to provide reference for further study of bioactive components of L.lucidus Turcz and development of functional products.【Method】Triterpenic acid in L.lucidus Turcz was extracted through ethanol extraction method.Ethanol volume fraction，solid-liquid ratio，extraction temperature and extraction time were taken as the influencing factors，and the extraction amount of triterpenic acid was taken as the evaluation index.The extraction process of triterpenic acid was optimized by single factor test and response surface optimization test.The scavenging rates of 2,2-diphenyl-1-picrylhydrazyl radical（DPPH· ），2,2-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid radical（ABTS⁺）and hydroxyl radical（·OH）were determined，and ascorbic acid（Vc）was used as a positive control.【Result】 The effects of 4 factors on the extraction effect of triterpenic acid from L.lucidus Turcz were ranked as follows： ethanol volume fraction>solid-liquid ratio>extraction temperature>extraction time，among which ethanol volume fraction had extremely significant effect（P< 0.01），the solid-liquid ratio and extraction temperature had significant effects（P<0.05），the interaction between the two factors had no significant effect on the extraction of triterpenic acid from L.lucidus Turcz（P>0.05）.The optimal extraction conditions were as follows： extraction time of 2.0 h，ethanol volume fraction of 95%，solid-liquid ratio of 1∶40 and extraction temperature of 50℃.Under these conditions，the extraction amount of triterpenic acid from L.lucidus Turcz was 1.9431 mg/g，which was little different from the theoretical value（1.9440 mg/g）.The results of antioxidant activity showed that the maximum scavenging rates of DPPH·，ABTS⁺ and·OH were 87.46%，97.57% and 46.78%，respectively.Although the scavenging rates of triterpenic acid were lower than those of Vc，it still had antioxidant activity.【Conclusion】 The method of response surface optimization for extracting triterpenic acid from L.lucidus Turcz is reliable，and L.lucidus Turcz triterpenic acid has certain antioxidant activity，which can be developed into functional products.