45. Hepatoprotective action of an oleanolic acid-enriched extract
of Ligustrum lucidum fruits
is mediated through an enhancement on hepatic glutathione regeneration capacity
Yim TK, Wu WK, Pak WF, Ko KM.
Department of Biochemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
The fruits of Ligustrum lucidum Ait. (FLL) were fractionated into petroleum ether (FLL-Pe), chloroform (FLL-Ch), butanol (FLL-Bu) and aqueous (FLL-Aq) fractions, of which FLL-Ch and FLL-Bu were found to be enriched with oleanolic acid (OLA). The in vivo antioxidant activities of various FLL fractions and OLA were assessed by examining the effect on carbon tetrachloride (CCl(4))-induced hepatotoxicity in mice. Pretreatment of animals with various FLL fractions could protect against CCl(4)-induced hepatotoxicity to a varying degree, with OLA-enriched FLL-Bu and FLL-Ch being more potent. However, a mortality rate of 60% was observed in the FLL-Ch pretreated and CCl(4)-intoxicated mice. OLA pretreatment also produced a dose-dependent protection against CCl(4) hepatotoxicity. The hepatoprotection afforded by FLL-Bu or OLA pretreatment was associated with an enhancement of hepatic-glutathione regeneration capacity (GRC). In contrast, the inability of FLL-Aq pretreatment to enhance hepatic GRC resulted in a failure to prevent CCl(4)-induced hepatic injury. The results suggest that the hepatoprotective action afforded by OLA-enriched FLL-Bu or OLA pretreatment may be mainly mediated by the enhancement of hepatic GRC, particularly under conditions of CCl(4)-induced oxidative stress. Copyright 2001 John Wiley & Sons, Ltd.