Solvent extraction of caffeoylquinic acids from Artemisia selengensis Turcz leaves and their in vitro inhibitory activities on xanthine oxidase

In this study, the caffeoylquinic acid (CQA) extract solution of the Artemisia selengensis Turcz (AST) leaves prepared by 70% ethanol reflux method was separated with petroleum ether, ethyl acetate, and water-saturated n-butanol to obtain the proper solvent to purify CQAs. Results showed that the ethyl acetate fraction (EAF) exhibited the highest total chlorogenic acid content (TCC) (241.46 ± 0.00 mg/g dry fraction), followed by the water-saturated n-butanol fraction (nBuF) (TCC = 62.30 ± 0.82 mg/g dry fraction). Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry and high-performance liquid chromatography photodiode array were used to qualitatively and quantitatively determine the CQAs in these two fractions. In EAF, four CQAs, namely, 3-CQA, 3,5-diCQA, 3,4-diCQA, and 4,5-diCQA, were identified with the contents of 5.69 ± 0.03, 106.65 ± 0.83, 15.65 ± 0.24, and 28.08 ± 0.82 mg/g, respectively. Six CQAs, namely, 3-CQA, 4-CQA, 1,3-diCQA, 3,5-diCQA, 3,4-diCQA, and 4,5-diCQA, with contents of 16.57 ± 0.23, 3.22 ± 0.55, 4.49 ± 0.01, 16.86 ± 0.24, 7.35 ± 0.11, and 6.41 ± 0.13 mg/g, respectively, were identified in nBuF. Quantitative analysis of the six CQAs in AST leaves have not been reported, and 1,3-diCQA has been found in AST leaves for the first time. Moreover, either EAF or nBuF and the six CQA reference compounds showed certain inhibitory activity on xanthine oxidase (XOD) in vitro. EAF demonstrated a stronger XOD inhibitory effect (IC50 = 1.67 mg/mL) than nBuF. Among the six CQA compounds, 3,4-diCQA had the lowest IC50 of 12.80 μM, whereas 1,3-diCQA and 3-CQA had IC50 values of 23.69 and 28.29 μM, respectively. The inhibitory activity of 4-CQA was weak. These findings indicated that CQAs are the major components inhibiting the XOD activity in vitro in AST leaves.