Extraction process optimization of total flavonoids from Coreopsis tinctoria Nutt and evaluation of antioxidant activity of different solvent extracts

Objective The optimization of extraction conditions of total flavonoids from Coreopsis tinctoria (C. tinctoria) was studied, and the antioxidant activities of the extracts with different solvents were evaluated.

Methods Mixed solvents of ethanol and water was used to extract total flavonoids of C. tinctoria by optimization design of single factors and orthogonal test. Next, the mixture of the total flavonoids was fractionally extracted with different organic solvents. The extraction rate of flavonoids, antioxidant activity, and the content of characteristic components of marein and flavanomarein were measured and compared.

Results The optimal conditions for extraction of the total C, tinctoria flavonoids were 75% ethanol, 1∶10 (g/mL) solid-liquid ratio, reflux extraction at 80 ℃ for 120 min. The extraction rate of total flavonoids was 27.52%. Among the different organic solvent extracts, the n-butanol extract had the highest extraction yield (11.20%) and the highest quality of (458.2 ± 0.11) mg/g. The ethyl acetate extract yielded 10.17% of extraction yield and (276.4 ± 0.19) mg/g of total flavonoids. The four kinds of solvent extracts all had certain antioxidant activities, and the order of antioxidant capacity from high to low was n-butanol > ethyl acetate > dichloromethane > hexane. In the range of 0.03～1.00 mg/mL, the antioxidant activity increased with the increase of the mass concentration of the extract. When the mass concentration reached 1.00 mg/mL, the antioxidant activities of n-butanol extracts and ethyl acetate extracts were approximately the same. The concentrations of marein and flavonomarein in n-butanol extract were (382.02 ± 0.42) mg/g and (92.35 ± 0.53) mg/g, respectively, and those in ethyl acetate extract were (262.15 ± 0.07) mg/g and (23.81 ± 0.12) mg/g, respectively.

Conclusion In this study, the optimized extraction process of total flavonoids from Coreopsis tinctoria yielded a total flavonoid extraction rate of 27.52%, among which, n-butanol extract and ethyl acetate extract had better antioxidant activity in vitro, and both were rich in characteristic components of marein and flavonomarein. Therefore, these two kinds of solvent extracts can be used as key research resources for further purification of monomer flavonoid compounds of Coreopsis tinctoria.