Characterization and hepatoprotective evaluation of sesquiterpenes and diterpenes from the aerial parts of Juniperus sabina L.

Previously, we reported on the hepatoprotective activity of the total extract of Juniperus sabina L. against CCl₄ induced liver toxicity in experimental animals. Biologically directed phytochemical study was conducted to identify the active compounds. Male Wistar rats and the standard drug silymarin were used in the study. Hepatoprotective activity was evaluated via serum biochemical parameters such as aspartate amino transferase (AST), alanine aminotransferase (ALT), gamma glutamyl transpeptidase (GGT), alkaline phosphatase (ALP) and total bilirubin. Tissue parameters including non-protein sulfhydryl groups (NP-SH), malonaldehyde (MDA) and total protein (TP) were also determined. Histopathological study was conducted utilizing Mayer's hematoxylin stain, Periodic Acid Schiff – Hematoxylin (PAS-H) and Masson trichrome technique on light microscope. Electron microscope images were also generated for the study. The activity of the total extract was trapped to the petroleum ether fraction after liquid-liquid fractionation where 51% reduction in the levels of AST, bilirubin and 44% in the levels of ALT were observed. Chromatographic purification of the petroleum ether fraction resulted in the isolation of nine compounds namely: trans-calamenene (1), cadalene (cadalin) (2), epi-cubenol (3), manool (4), calamenene-10β-ol (5), calamenene-10α-ol (6), 4-epi-abietic acid (7), sandaracopimaric acid (8) and isopimaric acid (9). Compounds 1–3, 5 and 6 are belonging to cadinane sesquiterepenes, while compounds 4, 7–9 were of diterpene skeleton. The major compounds were tested for their hepatoprotective effect. Compounds 3 showed marked improvement in the levels of AST and ALT, compound 4 was effective in improving the levels of AST, ALT, GGT, ALP and bilirubin, while compound 7 showed significant improvement in GGT, ALP and bilirubin levels.