Hepatotoxicity induced by radix Sophorae tonkinensis in mice and increased serum cholinesterase as a potential supplemental biomarker for liver injury

Radix Sophorae tonkinensis (S. tonkinensis) is used in Chinese folk medicine to treat sore throats, viral hepatitis, and jaundice. However, little is known about the hepatotoxicity induced by it. This study is to investigate hepatotoxicity induced by radix S. tonkinensis and a potential supplemental biomarker for liver injury through acute toxicity, accumulative toxicity, tolerance test, and sub-chronic toxicity. The contents of cytisine (CYT), matrine (MT), and oxymatrine (OMT) in radix S. tonkinensis extracts were determined simultaneously by the method we developed. In the acute toxicity study, mice were scheduled for single oral gavage at doses of 0, 2.4, 3.2, 4.2, 5.6, 7.5 g/kg of radix S. tonkinensis extracts respectively. Another three groups of mice received radix S. tonkinensis extracts orally in single doses of 0, 4.3, 5.6 g/kg, while the two groups of the hepatic injury model were induced by intraperitoneal injection with 0.1% and 0.2% carbon tetrachloride (CCl₄). Mortality rate, analysis of serum biochemistry, and histopathological examination were used to assess the acute toxicity. In the accumulative toxicity study, mice were treated radix S. tonkinensis extracts orally by the method of dose escalation for 20 days respectively. Accumulative toxicity was assessed by mortality rate. In the tolerance test, half of the mice of test group in the accumulative toxicity were administered the dose of 4.3 g/kg radix S. tonkinensis extracts, and the rest of the mice in the test group were assigned to receive the dose of 5.6 g/kg radix S. tonkinensis extracts. In the sub-chronic toxicity study, mice were treated with daily doses of 0, 0.25, 1.0, 2.5 g/kg radix S. tonkinensis extracts for 90 days. Assessments of body weights, serum biochemical analysis, and histopathological examination were performed. An enzyme-inhibition assay for butyrylcholinesterase (BuChE) and acetylcholinesterase (AChE) of CYT, MT, and OMT was also carried out. The contents of CYT, MT, and OMT in radix S. tonkinensis extracts were 5.63 mg/g, 27.63 mg/g, and 16.20 mg/g respectively. In the acute toxicity study, LD50 of radix S. tonkinensis extracts was 4.3 g/kg. No mice were found dead in the accumulative toxicity study. In the acute toxicity and tolerance test, increased ALT, AST, and CHE levels were observed in a dose-response manner, while the severity of histological changes in liver was shown in a dose-dependent mode. In the sub-chronic toxicity, though there was a decline trend of ALT and AST levels found in 0.25 g/kg, 1.0 g/kg, and 2.5 g/kg radix S. tonkinensis extracts as compared to control, which might be related to weight loss, the severity of histopathological changes in the liver and the increased serum CHE level was shown in a dose-response manner. MT, OMT, and CYT showed inhibitory effects on BuChE and AChE in the enzyme-inhibition assay. The results of this study indicate that radix S. tonkinensis should have hepatotoxicity, and increased serum CHE is a potential supplemental biomarker for liver injury.