Hepatoprotective effects of extracts, fractions and compounds from the stem bark of Pentaclethra macrophylla Benth: Evidence from in vitro and in vivo studies

Aim: To identify the bioactive hepatoprotective components of the ethanol extract of Pentaclethra macrophylla stem bark using in vitro and in vivo approaches. Methods: The bioguided-fractionation of the ethanol extract was based on the substances' capacity to prevent in vitro, the lipid peroxidation of hepatocytes' membranes induced by hydrogen peroxide. For the in vivo hepatoprotective test, mice were treated orally with the ethyl acetate (EtOAc) fraction of the ethanol extract at doses of 50 and 75 mg/kg/day for one week and subjected to D-galactosamine/lipopolysaccharide (GaIN/LPS)-induced hepatotoxicity. Blood samples were collected for alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), TNF-alpha and IL-l beta assays. The liver was harvested for histological and biochemical (proteins, glutathione (GSH), catalase and superoxide dismutase (SOD)) analysis. Results: The ethanol extract and fractions induced concentration-dependent inhibition of lipid peroxidation (IC50: 3.21-48.90 mu g/mL) greater than that of silymarin (IC50: 117.4 mu g/mL). The purification of the sub-fractions of EtOAc fraction yielded: (7R)-7-hydroxyhexacosanoic acid (1), (7R)-1-(7-hydroxyhexacosanoyl) glycerol (2), bergenin (3), 11-O-galloylbergenin (4), 2-hydroxymethyl-5-(2-hydroxypropan-2-yl)phenol (5), beta-sitosteml 3-O-beta-D-glucopyranosyl (6) and beta-sitosterol (7)), among which 11-O-galloylbergenin (IC50:1.8 mu g/mL) was the most effective. The EtOAc fraction significantly reduced the serum level of ALAT, ASAT and TNF-alpha in vivo. This EtOAc fraction increased the liver protein content and protected the liver against structural damages, but did not boost the endogenous antioxidant parameters. Conclusion: The stem bark of Pentaclethra macrophylla possesses hepatoprotective effects that may result from its capacity to inhibit lipid peroxidation and could be attributed to its active components 3, 4 and 2.