Metabolic characteristics of Tanshinone I in human liver microsomes and S9 subcellular fractions

Abstract

Tanshinone I (TSI) is a lipophilic diterpene in Salvia miltiorrhiza with versatile pharmacological activities. However, metabolic pathway of TSI in human is unknown. In this study, we determined major metabolites of TSI using a preparation of human liver microsomes (HLMs) by HPLC-UV and Q-Trap mass spectrometer. A total of 6 metabolites were detected, which indicated the presence of hydroxylation, reduction as well as glucuronidation. Selective chemical inhibition and purified cytochrome P450 (CYP450) isoform screening experiments revealed that CYP2A6 was primarily responsible for TSI Phase I metabolism. Part of generated hydroxylated TSI was glucuronidated via several glucuronosyltransferase (UGT) isoforms including UGT1A1, UGT1A3, UGT1A7, UGT1A9, as well as extrahepatic expressed isoforms UGT1A8 and UGT1A10. TSI could be reduced to a relatively unstable hydroquinone intermediate by NAD(P)H: quinone oxidoreductase 1 (NQO1), and then immediately conjugated with glucuronic acid by a panel of UGTs, especially UGT1A9, UGT1A1 and UGT1A8. Additionally, NQO1 could also reduce hydroxylated TSI to a hydroquinone intermediate, which was immediately glucuronidated by UGT1A1. The study demonstrated that hydroxylation, reduction as well as glucuronidation were the major pathways for TSI biotransformation, and six metabolites generated by CYPs, NQO1 and UGTs were found in HLMs and S9 subcellular fractions.

High fat diet significantly changed the global gene expression profile involved in hepatic drug metabolism and pharmacokinetic system in mice

“…Ugt1a9 encodes an enzyme responsible for hydroxyl and phenol glucuronidation. Substrates of UGT1A9 involve lots of nature products such as flavonoids, tanshinone, and some alkaloids [16][17][18][19], as well as important synthetic drugs such as propofol [20], 4methylumbelliferone [21], mycophenolic acid [22], and morphine [23]. In addition, UGT1A9 also participated in metabolism processes of endogenous signaling molecules like estradiol [24].…”

An Overview of Biotransformation and Toxicity of Diterpenes

“…The biotransformation of tanshinone I with human liver microsomes and S9 subcellular fractions afforded similar metabolites than the ones described in the different biotransformation approaches, by hydroxylation, reduction, and glucuronidation enzymatic reactions ( Figure 7 ) [ 52 ]. The investigation of the enzymatic isoforms involved in the bioconversions showed that CYP2A6 was primarily responsible for phase I metabolites (compounds 4.1 and 4.2 , Figure 7 ), and UGT1A1, UGT1A3, UGT1A7, UGT1A9, UGT1A8, and UGT1A10 were involved in phase II metabolism (compounds 4.3 – 4.6 , Figure 7 ).…”

“… Proposed metabolic pathways and enzyme isoforms involved in the biotransformation of tanshinone I ( 4 ) by human liver microsomes and S9 subcellular fractions [ 52 ]. …”

Metalloporphyrins in Medicine: From History to Recent Trends

“…At the same time, other MeP with different metals and properties appeared. In 1960, cytochrome P450 was extracted from liver microsomes . The researchers identified the role of cytochrome P450 as an important enzyme, which catalyzes the hydroxylation of various substrates (fatty acids, steroids, etc .).…”