title: Evaluation and Comparison of the Inhibition Effect of Astragaloside IV and Aglycone Cycloastragenol on Various UDP-Glucuronosyltransferase (UGT) Isoforms.
abstract: As one of the main active ingredients from Radix Astragali (RA), orally dosed astragaloside IV (AST) is easily transformed to sapogenin-cycloastragenol (CAG) by deglycosylation in the gastrointestinal tract. Because the potential adverse effects of AST and CAG remain unclear, the present study in this article was carried out to investigate the inhibition effects of AST and CAG on UDP-glucuronosyltransferases (UGTs) to explore potential clinical toxicity. An in vitro UGTs incubation mixture was employed to study the inhibition of AST and CAG towards UGT isoforms. Concentrations of 100 μM for each compound were used to initially screen the inhibitory efficiency. Deglycosylation of AST to CAG could strongly increase the inhibitory effects towards almost all of the tested UGT isoforms, with an IC50of 0.84 μM and 11.28 μM for UGT1A8 and UGT2B7, respectively. Ulteriorly, the inhibition type and kinetics of CAG towards UGT1A8 and UGT2B7 were evaluated depending on the initial screening results. Data fitting using Dixon and Lineweaver-Burk plots demonstrated that CAG competitively inhibited UGT1A8 and noncompetitively inhibited UGT2B7. From the second plot drawn with the slopes from the Lineweaver-Burk plot versus the concentrations of CAG, the inhibition constant (Ki) was calculated to be 0.034 μM and 20.98 μM for the inhibition of UGT1A8 and UGT2B7, respectively. Based on the [I]/Kistandard ([I]/Ki< 0.1, low possibility; 1 > [I]/Ki> 0.1, medium possibility; [I]/Ki> 1, high possibility), it was successfully predicted here that an in vivo herb-drug interaction between AST/CAG and drugs mainly undergoing UGT1A8- or UGT2B7-catalyzed metabolism might occur when the plasma concentration of CAG is above 0.034 μM and 20.98 μM, respectively.
authors.affiliation: Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnosis, School of Pharmacy, Tianjin Medical University, Tianjin 300070, China.
authors.forename: Ruixue
authors.initials: R
authors.lastname: Ran
authors.affiliation: Department of Colorectal Surgery, Tianjin Union Medical Center, Tianjin 300121, China. zhangchunzetj@163.com.
authors.forename: Chunze
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnosis, School of Pharmacy, Tianjin Medical University, Tianjin 300070, China.
authors.forename: Rongshan
authors.initials: R
authors.lastname: Li
authors.affiliation: Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnosis, School of Pharmacy, Tianjin Medical University, Tianjin 300070, China.
authors.forename: Bowei
authors.initials: B
authors.lastname: Chen
authors.affiliation: Department of Colorectal Surgery, Tianjin Union Medical Center, Tianjin 300121, China. woshifangzhongze@163.com.
authors.forename: Weihua
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Pharmacy, Tianjin Union Medical Center, Tianjin 300121, China. clinpharmzhao@163.com.
authors.forename: Zhenying
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: Department of Toxicology, School of Public Health, Tianjin Medical University, Tianjin 300070, China. fffffzhiwei@163.com.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Fu
authors.affiliation: Department of Toxicology, School of Public Health, Tianjin Medical University, Tianjin 300070, China. zsjz2113@sina.com.
authors.forename: Zuo
authors.initials: Z
authors.lastname: Du
authors.affiliation: Key Laboratory of Cancer Prevention and Therapy, National Clinical Research Center for Cancer, Department of Pharmacy, Tianjin Medical University Cancer Institute and Hospital, Tianjin 300060, China. duxiaolang1988@126.com.
authors.forename: Xiaolang
authors.initials: X
authors.lastname: Du
authors.affiliation: Department of Rehab and Sports Medicine, Tianjin Medical University, Tianjin 300070, China. yxl0925@sina.com.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Toxicology, School of Public Health, Tianjin Medical University, Tianjin 300070, China. fangzhongze@tmu.edu.cn.
authors.forename: Zhongze
authors.initials: Z
authors.lastname: Fang
mesh_terms: D004365:Drugs, Chinese Herbal; D014453:Glucuronosyltransferase / Q000037:antagonists & inhibitors*; D041743:Herb-Drug Interactions; D020033:Protein Isoforms / Q000037:antagonists & inhibitors; D012502:Sapogenins / Q000493:pharmacokinetics* / Q000494:pharmacology*; D012503:Saponins / Q000493:pharmacokinetics* / Q000494:pharmacology*; D014315:Triterpenes / Q000493:pharmacokinetics* / Q000494:pharmacology*
chemical_list: D004365:Drugs, Chinese Herbal; D020033:Protein Isoforms; D012502:Sapogenins; D012503:Saponins; D014315:Triterpenes; C052064:astragaloside A; D014453:Glucuronosyltransferase; C454320:UDP-glucuronosyltransferase, UGT1A8; C061014:cycloastragenol
keywords: UDP-glucuronosyltransferases (UGTs); astragaloside IV; cycloastragenol; herb–drug interactions