Antioxidant, antimicrobial and antiverotoxic potentials of extracts of Curtisia dentate

Abstract

The potentials of Curtisia dentata as antimicrobial, antioxidant and antiverotoxin against environmental isolates of E. coli and Acinetobacter spp, the presence of phytochemicals and some organic compounds was investigated. The highest concentration of phytochemicals and organic compounds such as anthraquinones, alkaloids, essential oils, glycosides, phenols, steroids, saponins and tannins and the organic compounds quinones, anthocyanins, amines and carboxylic acids were found in the stem bark ethanol extracts compared to other parts of the plant or solvent extracts. Antimicrobial activity as relative inhibition zone diameters (%) ranged between 8-28% (MIC values, 100- 2500 mg/ml) against E. coli serotypes, and 10-28% (MIC, 100-850mg/ml) and 6-28% (MIC, 150-2500 mg/ml) against A. lwoffii and A. haemolyticus respectively. The extracts demonstrated inhibitory action against the expression of both Vtx1 and Vtx2 genes in both E. coli and A. haemolyticus strains with the ethanol extracts demonstrating the highest antiverotoxic activity compared to other solvents. The ethanol root bark extracts consistently showed the highest DPPH radical scavenging activity (62.43%), total phenol content (TPH) (57.62 26 mg GAE/g) and reducing power (RP) (41.32%), followed by those of the stem bark and leaf extracts with the respective values of 54.68%, 37.77 mg GAE/g and 21.83%. Ethanol extracts demonstrated the highest values for both DPPH, TPH and RP followed by dichloromethane, hexane, acetone and distilled water in this order. C. dentata can be used to source novel antimicrobial agents for the treatment of verotoxic bacterial infections.