Spicatic acid: A 4-carboxygentisic acid from Gentiana spicata extract with potential hepatoprotective activity

Due to our interest in bioactive plant derived materials, the hepatoprotective activity of the aqueous alcoholic extract of Gentiana spicata AEGS (Gentianaceae) on carbon tetrachloride treated rats was investigated. CCl4 used at a concentration of 1 mL/kg.b.wt. significantly increased the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). However, pre-treatment with AEGS and its individual components significantly prevented the increase in these enzymes, which are the major indicators of liver injury. Biochemical assays of liver homogenate showed that AEGS and its components restored reduced glutathione (GSH) depletion reduced the level of thiobarbituric acid reactive substances (TBARS). Furthermore, liver histological observation also showed an obvious amelioration in liver cell necrosis, liver lesions, and fatty changes in pre-treated groups. Phytochemical investigation of the extract showed high phenolic content and led to the isolation and identification of the new carboxygentisic acid, 1,4-dicarboxy 2,5-dihydroxybenzene, for which we suggest the name spicatic acid, together with the known flavonoids, quercetin 3-O-[(2,3,4-triacetyl-α-rhamnopyranosyl)1'''→6''] 3-acetyl-β-galactopyranoside and quercetin 3-O-[(2,3,4-triacetyl-α-rhamnopyranosyl)1'''→6'']-4-acetyl-β-galactopyranoside, epicatechin, catechin and their gallolyated derivatives. All structures were elucidated on the basis of conventional analytical methods and confirmed by high resolution ESIMS, 1D- and 2D-NMR data. The new phenolic 4-carboxygentisic acid, spicatic acid is of special interest as it represents the first phenolic acid in nature which bears two carboxyl functions in one aromatic ring.