Inhibition of xanthine oxidase by Rhodiola crenulata extracts and their phytochemicals.
Using a fractionation technique, four phytochemicals were isolated from Rhodiola crenulata extracts. These compounds were identified as 4'-hydroxyacetophenone (4-HAP), epicatechin-(4β,8)-epicatechin gallate (B2-3'-O-gallate), salidroside, and p-tyrosol using mass spectrometry and nuclear magnetic resonance spectroscopy. The inhibition of xanthine oxidase (XO) activity by these purified compounds was then evaluated and compared to that of a known XO inhibitor (allopurinol; IC50 = 12.21 ± 0.27 μM). Both 4-HAP and B2-3'-O-gallate showed an XO inhibitory effect, for which the half maximal inhibitory concentration (IC50) values were 15.62 ± 1.19 and 24.24 ± 1.80 μM, respectively. However, salidroside and p-tyrosol did not show significant inhibitory effects on XO at 30 μM. Furthermore, an inhibition kinetics study indicated that 4-HAP and B2-3'-O-gallate are mixed competitive inhibitors. The inhibition constants (Ki) of 4-HAP and B2-3'-O-gallate were 8.41 ± 1.03 and 6.16 ± 1.56 μM, respectively. These results suggest that 4-HAP and B2-3'-O-gallate are potent XO inhibitors.
Department of Food Science, Fu Jen Catholic University , 510 Zhongzheng Road, Xinzhuang, Taipei 24205, Taiwan.
Yung-Hung
YH
Chu
Chao-Jung
CJ
Chen
Shih-Hsiung
SH
Wu
Jung-Feng
JF
Hsieh
D004791:Enzyme Inhibitors / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D015394:Molecular Structure; D064209:Phytochemicals / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry*; D029771:Rhodiola / Q000737:chemistry*; D014969:Xanthine Oxidase / Q000037:antagonists & inhibitors* / Q000737:chemistry
D004791:Enzyme Inhibitors; D064209:Phytochemicals; D010936:Plant Extracts; D014969:Xanthine Oxidase