Biological Activities and Isolation of Bioactive Compounds from Zanthoxylum thouvenotii H. Perr. (Rutaceae) Bark

Abstract

Background: Zanthoxylum thouvenotii H. Perr. (Rutaceae) is used in Malagasy traditional medicine for toothache, malaria and metabolic disorders, but information on the biological activities and chemical constituents of its bark remains limited. Aim: This study evaluated the anti-hyperglycaemic, antimicrobial, antioxidant and anti-inflammatory activities of bark extracts and isolated bioactive constituents. Methods: Air-dried bark was extracted with ethanol/water and cyclohexane to obtain EE1, CE and EE2. Phytochemical screening was performed on EE1. Acute oral toxicity, antimicrobial activity by disc diffusion, hypoglycaemic activity in glucose-induced transient and high-fat diet-induced chronic hyperglycaemia, antioxidant activity by DPPH bioautography and anti-inflammatory activity using carrageenan-induced paw oedema were assessed. The active cyclohexane extract was fractionated by silica gel column chromatography, and isolated compounds were identified using NMR data. Results: EE1 contained steroids, alkaloids and triterpenoids, showed no mortality or clinical signs of acute toxicity up to 5 g/kg, and produced inhibition zones below 7 mm against the tested microorganisms. In the transient hyperglycaemia model, EE1 reduced blood glucose to 7.0 ± 0.8 mmol/L at 200 mg/kg after glucose administration, but did not restore glycaemia in obese mice. CE and EE2 were positive in the DPPH assay and inhibited carrageenan-induced oedema by 66.63% and 45.12%, respectively, at 250 mg/kg after 2 h. Fractionation of CE yielded lupeol and a mixture of β-sitosterol and stigmasterol. Lupeol inhibited paw oedema by 83.76% at 25 mg/kg. Conclusion: The findings indicate that Z. thouvenotii bark contains compounds associated with antioxidant and anti-inflammatory activity, with lupeol contributing to the observed anti-inflammatory effect.