Chemical constituents and anti-ulcer activity of propolis from the North-West region of Cameroon

Abstract

Three extracts of propolis harvested from Nkambe, North-West region of Cameroon were characterized by GC-MS analysis and their gastric cytoprotective, antisecretory and antioxidant properties evaluated using experimentally-induced gastric ulcers in rats. The propolis extracts were rich in phytoconstituents occurring as sugars, triterpenes and a mixture (fatty acids+triterpenes+alkenyl resorcinols) in the methanol, hexane and acetone extracts, respectively with Mangifera indica as major plant source. Three triterpenes, lupeol, lupenone, 27-hydroxymangiferonic acid and an ester of fatty acid heptadecyl butanoate were isolated and characterized. The methanol, acetone and hexane extracts (200-600 mg kg-1) dose-dependently prevented the formation of ethanol-induced gastric lesions (percentage of inhibition, 61, 54 and 55%, respectively, at the dose of 600 mg kg-1). Increasing doses of the extracts inhibited pylorus ligation-induced lesions by 64.5, 73.1 and 16.2%, respectively for the highest dose but none of them showed antisecretory activity compared with controls. The most further significantly (p < 0.01) reduced HCl/ethanol-induced ulcer indices from 4.33+0.32 in cytoprotective (acetone) extract (56.6-73.1% inhibition under highly acidic gastric environments), the controls to 1.25+0.53 and 0.6+0.04 at the dose of 400 and 600 mg kg-1, respectively (percentage of inhibition: 71-86%). Furthermore, upon pretreatment of the rats with indomethacin prior to HCl/ethanol, the acetone extract significantly (p < 0.001) decreased ulcer index from 5.55+0.73 in the controls to 1.89+0.15 at the dose of 600 mg kg-1. Although pretreatment with indomethacin reduced the protective effect of the acetone extract by 23-27% and cytoprotection remained high (62-66% inhibition). The cytoprotective action of the most active (acetone) extract may involve the mediation of endogenous prostaglandins.