Objective: To preliminarily investigate whether the hepatotoxicity of Sophorae Tonkinensis Radix et Rhizoma is associated with cytisine (CYT) by researching the hepatotoxicity of CYT in vivo and in vitro. Method: AML12 liver cells were cultured and employed as an in vitro model for hepatotoxicity. Cell viability of CYT was detected with a cell counting Kit-8 (CCK-8) assay. After various final concentrations of CYT (6

10

14 mmol·L-1) were added and treated for 3

6

12 and 24 h

the levels of alanine aminotransferase (ALT)

aspartate aminotransferase (AST)

total bilirubin (TBIL) and lactic dehydrogenase (LDH) in culture medium were measured. In the acute toxicity study

mice were administered with CYT by gavage at doses of 0

24.8

33.1

44.2

58.9

78.5 mg·kg-1

respectively. In the sub-chronic toxicity study

male mice were divided into three groups and orally treated with ultrapure water (11.2 mg·kg-1 CYT and 14.0 mg·kg-1 CYT) for 90 days. At the end of administration

the mice were anaesthetized for collecting serum and testing biochemical indicators

including ALT

AST

TBIL

LDH. Result: The half maximal inhibitory concentration (IC50) value of CYT was the 15.17 mmol·L-1. Since the treatment with 14 mmol·L-1 for 6 h

LDH release robustly increased

peaked at 12 h (P<0.05

P<0.01)

and declined at 24 h (P<0.01). Furthermore

in cells treated with 14 mmol·L-1 CYT

the levels of LDH started to significantly increase at 6 h at the earliest (P<0.01)

peaked at 12 h (P<0.01)

and declined thereafter (P<0.01). However

6

10

14 mmol·L-1 CYT were found to have no effect on TBIL release. In the acute toxicity

median lethal dose (LD50) of CYT was 48.16 mg·kg-1 and belonged to grade 2 in the globally harmonized system of classification and labeling of chemicals (GSH). In the sub-chronic toxicity

compared with the blank control group

no significant change in ALT and LDH levels was observed in CYT treated mice. Although animals treated with 14.0 mg·kg-1 CYT showed lower AST (P<0.05) and higher TBIL (P<0.05)

these findings were unable to be correlated with the changes of enzyme activities induced by liver injury

since these parameters were within the background data range of our laboratory. There were no significant change in histopathological examination compared with control and CYT treated mice in the liver. This results may be related to the facts that half of the mice died in 14.0 mg·kg-1 CYT treated group

which led to a decrease in the samples of biochemistry and hepatic histopathological examination. Conclusion: CYT belongs to the grade 2 toxic substance of GSH in oral acute toxicity. It has hepatocyte toxicity in vitro

but the hepatotoxicity in vivo and whether belonging to the hepatotoxic ingredient of radix Sophorae tonkinensis still needs to be further studied.