The aim of this study was to evaluate the effect of the chloroform extract of Terminalia catappa L. leaves (TCCE) on carbon tetrachloride (CCl4)-induced acute liver damage and D-galactosamine (D-GalN)-induced hepatocyte injury. Moreover, the effects of ursolic acid and asiatic acid, two isolated components of TCCE, on mitochondria and free radicals were investigated to determine the mechanism underlying the action of TCCE on hepatotoxicity. In the acute hepatic damage test, remarkable rises in the activity of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) (5.7-and 2.0-fold) induced by CCl4 were reversed and significant morphological changes were lessened with pre-treatment with 50 and 100mgkg 1 TCCE. In the hepatocyte injury experiment, the increases in ALT and AST levels (1.9-and 2.1-fold) in the medium of primary cultured hepatocytes induced by D-GalN were blocked by pre-treatment with 0.05, 0.1, 0.5gL 1 TCCE. In addition, Ca2+-induced mitochondrial swelling was dose-dependently inhibited by 50-500M ursolic acid and asiatic acid. Both ursolic acid and asiatic acid, at concentrations ranging from 50 to 500M, showed dose-dependent superoxide anion and hydroxyl radical scavenging activity. It can be concluded that TCCE has hepatoprotective activity and the mechanism is related to protection of liver mitochondria and the scavenging action on free radicals.

The protective effects of oleanolic acid (OA) on carbon tetrachloride (CCl4)-induced liver mitochondrial damage and the possible mechanisms were investigated. Pretreatment with OA prior to the administration of CCl4 significantly suppressed the increases of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) (4.2-and 19.9-fold, respectively) in a dose-dependent manner in mice. The dissipation of mitochondrial membrane potential (14.8%) and intra-mitochondrial Ca2+ overload (2.1-fold) in livers of CCl4-insulted mice were also dose-dependently prevented by pretreatment with 20, 50 or 100mg/kg OA. In addition, the effects of OA on liver mitochondria permeability transition (MPT) induced by Ca2+ were assessed by measuring the change in mitochondrial membrane potential, release of matrix Ca2+ and mitochondrial swelling in vitro. The results showed that preincubation with 50 or 100μg/ml OA obviously inhibited the Ca2+-induced mitochondrial swelling, mitochondrial membrane depolarization and intra-mitochondrial Ca2+ release. It could be concluded that OA has protective effects on liver mitochondria and the mechanisms underlying its protection may be related to its inhibitory action on MPT.

Terminalia catappa L. leaves have been shown to protect against acute liver injury produced by some hepatotoxicants, but the active components and mechanisms are not clear. This study was designed to characterize the protective effects of the chloroform fraction of the ethanol extract of T. catappa leaves (TCCE) against carbon tetrachloride (CCl4)-induced hepatotoxicity in mice, and analyze the changes in expression level of Interleukin-6 (IL-6) in the process. It was found that TCCE pretreatment (10 or 30mg/kg, ig) protected mice from CCl4 toxicity, as evidenced by the reversed alterations in serum alanine aminotransferase (sALT) and serum aspartate aminotransferase (sAST) activities. Additionally liver tissues were subjected to RT-PCR, Western blot and immunohistochemistry to analyze changes in IL-6 expression. It was found that TCCE markedly suppressed the CCl4-induced over-transcription of IL-6 gene. Consistent with the result, the expression of IL-6 protein was also blocked by TCCE in CCl4-stimulated mice, especially in the area around central vein on liver tissue section. In conclusion, TCCE is effective in protecting mice from the hepatotoxicity produced by CCl4, and the mechanisms underlying its protective effects may be related to the inhibition on the overexpression of IL-6 mainly around terminal hepatic vein.

The hepatoprotective effects of the extract of Terminalia catappa L. leaves (TCE) against D-Galactosamine (D-GalN)-induced liver injury and the mechanisms underlying its protection were studied. In acute hepatic injury test, it was found that serum ALT activity was remarkably increased (3.35-fold) after injection of D-GalN in mice. But with oral pretreatment of TCE (20, 50 and 100mg/kg/d) for 7 days, change in serum ALT was notably reversed. In primary cultured hepatocytes from fetal mice, it was found that cell viability was decreased by 45.0% after addition of D-GalN, while incubation with TCE (0.1, 0.5 and 1.0mg/ml) for 36 hours could prevent the decrease in a dose-dependent manner. Meanwhile, D-GalN-induced both the increase of AST level (1.9-fold) and the decrease of SOD activity (48.0%) in supernatant of primary cultured hepatocytes could also be inhibited by pretreatment with TCE. In order to study the possible mechanisms underlying its hepatoprotective effects, one effective component separated from TCE, 2a, 3b, 23-trihydroxyursane-12-en-28-oic acid (DHUA), was used to determine anti-mitochondrial swelling activity and superoxide radicals scavenging activity in vitro. It was found that at the concentration range of 50-500 mmol/L DHUA, Ca2+-induced mitochondrial swelling was dose-dependently inhibited, and superoxide radicals scavenging activity was also shown in a dose-dependent manner. It was concluded that TCE has hepatoprotective activity and the mechanisms underlying its protective effects may be related to the direct mitochondrion protection and strong scavenging activity on reactive oxygen species (ROS).

The possible inhibition of ursolic acid (UA) on mitochondrial permeability transition (MPT) in mouse liver was investigated to identify the mechanisms underlying the hepatoprotective effect of UA. The effect of UA on liver MPT induced by Ca2+ was assessed by measuring changes in mitochondrial volume, mitochondrial membrane potential (MMP), release of matrix Ca2+, and transfer of cytochrome c (Cyt c) and apoptosis-inducing factor (AIF) from the intermembrane space to the cytoplasm. The results showed that obvious mitochondrial swelling, loss of MMP, and release of matrix Ca2+ occurred after the addition of 50 lM Ca2+. However, preincubation with 20, 50 or 100 lg ml 1 UA significantly blocked the above changes. Addition of 100lg ml1 UA inhibited on mitochondrial swelling by 73.2% after 5min, while the MMP dissipating and Ca2+ releasing were, respectively, suppressed by 59.3% and 54.1% after 3min. In addition, Western blot analysis showed Cyt c and AIF transferred from mitochondrial pellet to the supernatant after the addition of 50lM Ca2+, but the process was significantly inhibited by various concentrations of UA. The results suggest that the mechanisms underlying the hepatoprotection of UA may be related to its direct inhibitory action on MPT.