Hepatoprotective Effect of Syringic Acid and Vanillic Acid on CCl4-Induced Liver Injury

The mycelia of the edible mushroom Lentinula edodes can be cultured in solid medium containing lignin, and the hot-water extracts (L.E.M.) is commercially available as a nutritional supplement. During the cultivation, phenolic compounds, such as syringic acid and vanillic acid, were produced by lignin-degrading peroxidase secreted from L. edodes mycelia. Since these compounds have radical scavenging activity, we examined their protective effect on oxidative stress in mice with CCl4-induced liver injury. We examined the hepatoprotective effect of syringic acid and vanillic acid on CCl4-induced chronic liver injury in mice. The injection of CCl4 into the peritoneal cavity caused an increase in the serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. The intravenous administration of syringic acid and vanillic acid significantly decreased the levels of the transaminases. Four weeks of CCl4 treatment caused a sufficiently excessive deposition of collagen fibrils. An examination of Azan-stained liver sections revealed that syringic acid and vanillic acid obviously suppressed collagen accumulation and significantly decreased the hepatic hydroxyproline content, which is the quantitative marker of fibrosis. Both of these compounds inhibited the activation of cultured hepatic stellate cells, which play a central role in liver fibrogenesis, and maintained hepatocyte viability. These data suggest that the administration of syringic acid and vanillic acid could suppress hepatic fibrosis in chronic liver injury.