Antibacterial and Synergistic Effects of Extracts of Allium cepa, Allium sativum, Zingiber officinale and Garcinia kola on Selected Bacterial Strains doi.org/10.26538/tjnpr/v5i4.28

Abstract

The rising cases of antibiotic resistance and the failure of many drugs has led to growing calls for a return to nature and the fighting powers of many natural products against infections as solutions. Therefore, this study was aimed at investigating the phytochemical, antibacterial and synergistic potency of the extracts of some of these natural plants viz.: Allium cepa, Allium sativum, Zingiber officinale and Garcinia kola against some selected bacterial strains which are sometimes used in antimicrobial resistance studies: Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae. Qualitative phytochemical analysis of the extracts showed that they contain varying amounts of alkaloids, flavonoids, glycosides, tannins, saponins and steroids. Aqueous, ethanol and hexane extracts of the plants were used in the investigations against the test microorganisms. Results obtained showed that the microorganisms were highly susceptible to the aqueous and ethanol extracts, but showed comparatively less susceptibility to hexane extracts which were mainly oily components. Compared to the other test strains, K. pneumoniae showed the most resistance to the extracts. Combinations of the extracts showed positive synergism as they produced higher antimicrobial effects on many of the organisms. The minimum inhibitory concentration (MIC) ranged from 25mg/mL to 200mg/mL. Aqueous extracts of the plants produced the lowest MIC value of 25mg/mL against most of the bacteria. Considering the increasing failure of conventional antibiotic therapies, the results of this study could be positive indications that natural plants, spices and foods could serve as possible alternatives or options in the management of many infections.