目的 对紫草素的立体异构单体阿卡宁的氧葡萄糖醛酸代谢通路进行研究和表征。方法 采用液相色谱和质谱联用方法检测阿卡宁和其葡萄糖醛酸化代谢产物；将阿卡宁在人肝微粒体（HLM）、人肾微粒体（HKM）以及重组人类葡萄糖醛酸转移酶（UGT）中孵育，观察代谢轮廓、筛选参与催化的重组单酶、考察酶动力学；通过相关性分析以及化学抑制实验阐明UGT单酶对阿卡宁的选择性。结果 阿卡宁在含尿苷5'-二磷酸葡萄糖醛酸（UDPGA）的HLM孵育中，可以检测到1个UGT代谢产物。UGT单酶筛选发现UGT1A9高选择性催化阿卡宁。酶动力学研究显示在HLM、HKM和UGT1A9中阿卡宁的UGT代谢都呈底物抑制模式，并且表观亲和常数（K_m）在3.75~4.50 μmol/L。阿卡宁和已知UGT1A9探针底物异丙酚在12例个体人肝中的UGT代谢具有很好的相关性，R²为0.88。化学抑制实验显示在HLM中，厚朴酚和尼氟灭酸对阿卡宁的UGT代谢具有明显的抑制作用；睾酮、雷公藤红素和尼罗替尼对阿卡宁的UGT代谢均无明显抑制作用。结论 UGT代谢是阿卡宁（紫草素）在人体的重要代谢途径之一，阿卡宁是人类UGT1A9的一个高选择性探针底物。

Objective To investigate and characterize the O-glucuronidation pathways of the S-stereoisomer of shikonin (alkannin). Methods Liquid chromatography and mass spectrometry were employed for the detection of akannin and its glucuronide. The incubation of alkannin in human liver microsomes (HLM), human kidney microsomes (HKM) and recombinant human UDP-glucuronyltransferases (UGT) were employed for the study of metabolism profile, the involved UGT isoforms and kinetic analysis. Recombinant human UGT screening, correlation study and chemical inhibition experiments were used for elucidation the selectivity of UGT isoform towards alkannin. Results In the incubation of alkannin in HLM with the presence of UDPGA, a single UGT metabolite was detected. The screening of the recombinant human UGTs found that UGT1A9 high selectively catalyzed the glucuronidation of alkannin. Kinetic analysis revealed the kinetic of alkannin in HLM, HKM and recombinant UGT1A9 all followed substrate inhibition model and the K_m values were 3.75-4.50 μmol/L. The glucuronidation of alkannin and propofol, a probe substrate of UGT1A9, in 12 individual HLM showed really good correlation, the correlation coefficient R² was 0.88. Chemical inhibition experiments indicated that HLM magnolol and niflumic acid showed obvious inhibition to alkannin glucuronidation; Testerone, celastrol, and nilotinib did not inhibit alkannin glucuronidation. Conclusion This study finds that UGT metabolism is an important metabolism pathway of alkannin in human, and alkannin is a highly selective probe substrate of human UGT1A9.

国家自然科学基金资助项目（81273590，81473181）