Antimicrobial and cyclooxygenase enzyme inhibitory activities of Sclerocarya birrea and Harpephyllum caffrum (Anacardiaceae) plant extracts

Abstract

The growing demand of medicinal plants is posing a major threat to biodiversity conservation. Sclerocarya birrea and Harpephyllum caffrum (Anacardiaceae) are traditionally used to treat numerous ailments increasing their susceptibility to overexploitation. The aim of the study was to evaluate the medicinal efficacy of renewable aerial parts of the plants using in vitro assays, thus providing a conservation measure by plant part substitution. Plant samples were sequentially extracted with petroleum ether, dichloromethane and 80% ethanol, sonicated on ice and concentrated under vacuum. Antimicrobial activities were determined by the minimum inhibition concentration (MIC) using the micro-dilution assay. The ability of extracts to inhibit COX-1 and COX-2 enzymes was used to evaluate anti-inflammatory activity. Ethanolic extracts of S. birrea and H. caffrum exhibited high antibacterial activity (MIC < 1.0 mg/ml). S. birrea twig extract was the most active with a total activity of 1609.1 ml/g against Bacillus subtilis and an MIC of 0.098 mg/ml. Petroleum ether and dichloromethane extracts exhibited high COX-1 (90.7–99.8%) and COX-2 (69–92.6%) enzyme inhibition at a concentration of 250 μg/ml. The extracts of S. birrea and H. caffrum exhibited high antimicrobial and anti-inflammatory properties. Based on these results, plant part substitution can be a practical conservation strategy for the two species.