Antibacterial Activity of Triterpenes from the Stem Bark and Heartwood of Erythrophleum suaveolens (Guill. & Perr.) Brenan

Abstract

The antibacterial activity of compounds isolated from the stem bark and sawdust of Erythrophleum suaveolens were evaluated. Extraction of the pulverized plants materials was carried out using hexane, ethyl acetate and methanol. Extracts were fractionated using column chromatography and fractions were examined using Nuclear Magnetic Resonance spectroscopy. Antibacterial activities against Acidobacterium capsulatum, Actinobacterium sp., Agrobacterium tumefaciens, Bacillus subtili, Ralstonia solanacearum, Enterococcus faecium, Escherichia coli, Pseudomonas syringae, Pseudomonas aeruginosa and Proteus mirabilis were also carried out. A novel triterpene, 21-acetoxylupenone and betulin were identified in the fractions from the stem bark of E. suaveolens while cycloeucalenol and stigmasterol were obtained from the sawdust extract fractions. Pseudomonas aeruginosa was resistant to all control antibiotics but was inhibited by 21- acetoxylupenone and cycloeucalenol with 23 mm and 24 mm diameter of Zones of Inhibition. Acidobacterium capsulatum, Actinobacterium sp., Agrobacterium tumefaciens, Ralstonia solanacearum, and Proteus mirabilis were completely inhibited at Minimum Bactericidal Concentration (MBC) of 50 µg/mL, while Bacillus subtilis, Enterococcus faecium, Escherichia coli, Pseudomonas syringae, and Pseudomonas aeruginosa were completely inhibited at MBC values of 100 µg/mL. Thus E. suaveolens stem bark and saw dust isolates can be used in the control of plants diseases where these pathogens are the causative agents.

Keywords: Antibacterial, Triterpenes, 21-acetoxylupenone, Cycloeucalenol, Betulin, Nigeria