In vitro antibacterial activity of Morinda citrifolia extracts against eight pathogenic bacteria species

Medical professionals continue to face a severe issue with the evolution of resistance to conventional antibiotics. The search for new novel compounds from plants has been proven to be the alternative solution. Morinda citrifolia is used traditionally for the treatment of infectious diseases. The present study investigates the antibacterial properties of M. citrifolia root, leaf, and fruit (fresh, dried, and fermented) extracts on three-gram-positive and five-gram-negative bacteria. The plant parts were processed and extracted in distilled water and ethanol (60%, 80%, and absolute (100%)). The antibacterial activities of the extracts were assessed in vitro using the agar well diffusion method, with Ciprofloxacin serving as the positive control. All the tests were conducted three times to obtain the average value of inhibition zones. Overall, root extracts showed the most significant antibacterial activity, followed by dried fruit, fermented fruit extract, fresh fruit, and the least leaf extract. Using one-way ANOVA and Tukey's post-hoc tests, the statistical analysis revealed significant differences in antibacterial activity among the extracts and solvent concentrations. The 100% ethanol extracts had significantly higher zones of inhibition compared to the other solvents. The most inhibitory activity was against Campylobacter spp. (21.33±1.80) for the 80% ethanol root extract. All the extracts of M. citrifolia were found to exhibit moderate antibacterial activity against all the bacteria pathogens. However, Enterococcus faecium, Campylobacter spp., and Bacillus cereus were most sensitive to all the plant extracts while Shigella spp. and Klebsiella spp. showed resistance to most extracts. This observed difference is significant for each strain extract depending on the bacteria strain and the type of solvent extract (p < 0.001). The findings indicate a promising antimicrobial potential of M. citrifolia extracts.