Isolation, identification, and in vivoevaluation of flavonoid fractions of chloroform/methanol extracts of Rheum emodi roots for their hepatoprotective activity in Wistar rats

Objective: Even though the rhizome of Rheum emodi (Chinese rhubarb) has been used since centuries as a traditional medicinal plant in treating a number of disease conditions, the bioactive components responsible for its hepatoprotective activity have not been identified. Therefore, we isolated, identified, and evaluated in vivo the compounds in chloroform/methanol extracts of Rheum emodi roots for their hepatoprotective activities in rats. Materials and Methods: Nine different fractions were collected by column chromatography and were further isolated and identified through thin layer chromatography (TLC) analysis for the presence of flavonoids. The isolated flavonoids containing fractions were then evaluated for their hepatoprotective activity in paracetamol-induced toxicity in male Wistar rats. Silymarin [50 mg/kg body weight (BW)] was used as a control hepatoprotective drug. To assess liver functions, serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), albumin, and bilirubin (total and direct) were determined. Results: Only five collected fractions (F₁to F₅) showed the presence of different flavonoids and the fraction F₂showed the presence of five different types of flavonoids. The isolated flavonoid containing fractions of Rheum emodi were significantly effective in decreasing the elevated the levels of ALT, AST, ALP, and bilirubin (total and direct) due to paracetamol-induced hepatotoxicity in Wistar rats. The fractions at dose level of 0.125 mL/kg BW showed significant hepatoprotective effects in rats. The fraction F₂at a dose level of 0.5 mL/kg BW showed the maximum therapeutic efficacy followed by the same fraction at 0.25 mL/kg BW and 0.125 mL/kg BW, fractions F₁, silymarin, F₃, F₄and F₅. Conclusion: The results suggest that isolated fractions of Rheum emodi roots contained flavonoids, which showed significant hepatoprotective activity in Wistar rats. Further investigations are however, required for the identification of individual flavonoids as well as other bioactive components in Rheum emodi roots, and to establish their structure and mechanism of action for their hepatoprotective activity.