Evaluation of Phytochemicals and Antimicrobial Potentials of Chromolaena odorata (L.) on Selected Human Pathogens

Aims: This research was designed to evaluate the phytochemicals present in the leaf extracts of Chromolaena odorata L. and their antimicrobial activities.

Methodology: Dried leaves of C. odorata were pulverized and subjected to ethanolic and aqueous extraction. The extracts were qualitatively and quantitatively screened for phytochemicals using standard methods. The inhibitory activity of the leaf extracts were evaluated against clinical pathogens; Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Klebsiella pneumoniae, Proteus mirabilis and Candida albicans using agar well diffusion technique at 100 mg/mL and 200 mg/mL concentrations.

Results: The ethanolic extract of C. odorata had a better percentage yield of 5.49 g, followed by aqueous extract (3.5 g). The phytochemical screening conducted on the extracts revealed the presence of flavonoid, alkaloid, saponin, cardiac glycoside, steroids, tannins and terpenoids. The ethanolic extract exhibited better antimicrobial activity on S. typhi, S. aureus, E. coli, Ps. aeruginosa and C. albicans compared to the aqueous extract. This could be as a result of the higher extraction capability of the ethanol to penetrate easily into the cellular membrane and dissolve the intracellular inclusions from the plant materials than the aqueous solvent. The zones of inhibition of ethanolic extract at 100 mg/mL ranges from 2.33±0.33 mm to 9.50±0.36 mm with the lowest efficacy observed on P. mirabilis and highest on S. aureus. S. typhi was susceptible to the aqueous extract of the plant at this concentration with inhibitory zone of 4.00±0.00 mm. The ethanolic extract of the plant was also effective against C. albicans with inhibitory zone of 4.17±0.17 mm at 100 mg/mL. Chloramphenicol inhibited all the test bacteria with the highest efficacy on E. coli (16.33±0.03 mm) and ketoconazole at 25 mg/mL had a better antifungal activity on C. albicans compared to the observed antifungal activities of the aqueous and ethanolic extracts of C. odorata at 100 mg/mL. Furthermore, the test organisms were more susceptible to the aqueous and ethanolic extracts of C. odorata at 200 mg/mL with zones of inhibition ranging from 3.23±0.15 mm to 12.33±0.33 mm. The lowest being observed on E.coli and highest on S. typhi (ethanolic extract). K. Pneumoniae and P. mirabilis were resistant to the aqueous extract of C. odorata. All the test bacteria were susceptible to the aqueous and ethanolic extracts of C. odorata at 200 mg/mL extracts concentration. Moreover, C. albicans was susceptible to the inhibitory effect of C. odorata at this concentration with inhibitory zones of 3.00±0.00 mm and 5.33±0.33 mm on aqueous and ethanolic extracts respectively.

Conclusion: The findings from this study revealed the antimicrobial activities of C. odorata on the test pathogens which are in close proximity in comparison with the synthetic antimicrobial agents and thus upon purification, can be harnessed as a lead for the development of natural products derived antimicrobials in drug discovery against infections caused by these human pathogens evaluated in this study.