Hepatoprotective naphthalene diglucoside from Neanotis wightiana aerial parts.

BACKGROUND: Neanotis wightiana (Wall. ex Wight & Arn) W.H. Lewis has been used in traditional medicine in India for the treatment of liver disorders. In fact, this plant is frequently used by the local people of Tripura for the treatment of liver disorder problems. In previous study on this plant we have isolated a hepatoprotective saponin, neanoside A.

PURPOSE: Evaluation of in vivo hepatoprotective effects of isolated compounds from N. wightiana aerial parts on serum hepatic-biomarkers in CCl4 - induced hepatotoxicity in rats to validate the traditional use of the plant.

STUDY DESIGN: This study was designed to isolate more hepatoprotective compounds from N. wightiana aerial parts and evaluate their in vivo hepatoprotective activity in animal model.

METHODS: The phytochemicals from the polar n-butanol fraction of methanolic extract of N. wightiana aerial parts were isolated by repeated column chromatography over Diaion HP-20 and silica gel. Among the isolated three compounds, two were known triterpenoids, ursolic acid and oleanolic acid. The new compound was named neanoside B and its structure was established as naphthalene diglucoside 1 on the basis of extensive spectroscopic (including 2D NMR) analysis. Furthermore, the hepatoprotective activity of 1 was evaluated on CCl4 -induced hepatic injured rats by oral administration at three doses (5, 10 mg and 20 mg/kg) for 7 d and the assay of serum hepatic injury marker enzymes, SGPT, SGOT, ALP and bilirubin contents and histopathological changes of injured liver tissue after 7 d The herbal hepatoprotective drug, silymarin (100 mg/kg) was as positive control.

RESULTS: The structure of the new compound, neanoside B (1) was elucidated as 1,4-dihydroxy-2-(methoxymethyl)naphthalen-3-yl-methyl-3-β-d-glucopyranosyl-(1→6)-β-d-glucopyranoside on the basis of extensive spectroscopic (including 2D-NMR) and chemical studies. The compound 1 exhibited significant in vivo hepatoprotective effect at the tested doses of 5, 10 and 20 mg/kg bw in CCl4 -induced hepatotoxicity in rats. In a dose-dependent manner, 1 normalized the elevated levels of hepatic injury marker enzymes, serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), alkaline phosphatase (ALP) and total bilirubin and ameliorated the damage of liver tissue by reducing the necrosis and vacuoles. Possibly compound 1 ameliorated the hepatic damage in hepatotoxic rats by improving the antioxidant status. The higher dose (20 mg/kg) showed more hepatoprotective effect by reducing the elevated levels of SGPT, SGOT, ALP and bilirubin content to 388.5 ± 2.156, 160.7 ± 3.00, 198.6 ± 4.562 and 0.652 ± 0.036 IU/ml, respectively, compared to the levels in the control group (583.2 ± 6.922, 324.6 ± 4.711, 263.9 ± 4.939 and 1.533 ± 0.042 IU/ml, respectively) and the effect was comparable to that of the positive control silymarin (100 mg/kg bw) (389.4 ± 6.348, 167.9 ± 4.289, 203.3 ± 4.448 and 0.816 ± 0.030 IU/ml, respectively).

CONCLUSIONS: This study indicated that isolated neanoside B (1) from Neanotis wightiana could be a potential drug in liver disorders. Further study in pharmacokinetics and long-term toxicity of compound 1 is requested for its clinical setting as effective drug in liver disorders.