Abstract
The antimicrobial activities of the aqueous, ethanol and n-hexane fruit pulp extracts of Dialium guineense were evaluated against clinical isolates of Klebsiella pneumonia, Staphylococus aureus, Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis and Candida albicans using the agar well diffusion technique. The results reveal that the crude aqueous and ethanol extracts possess antimicrobial activities on the tested organisms with the exception of n-hexane extract which showed no zone of inhibition. The highest zone of inhibition diameter at 24.67 mm of the ethanol extract and 19.33 mm of the aqueous extract was recorded against C. albicans while S. aureus showed the lowest inhibition zone to the aqueous extract with 7.33 mm in diameter. However, statistical analysis indicates no significance as P>0.05. The minimum inhibitory concentration (MIC) of the aqueous and ethanol extracts to the isolates was between 100 - 200 mg/ml with only C. albicans at 50 mg/ml of the ethanol extract. Also, the minimum lethal concentration (MLC) of the aqueous and ethanol extracts on majority of the organisms was above 200 mg/ml but P. aeruginosa and P. mirabilis showed MLC at 200 mg/ml and, C. albicans at 100 mg/ml of the ethanol extract. Meanwhile, only C. albicans showed MLC to the aqueous extract at 100 mg/ml. In addition, the phytochemical screening revealed the presence of flavonoids, alkaloids, tannin, saponins, oxalates and glycosides. The results of this work suggest further exploitation of the fruit pulp of D. guineense to possibly unveil its potential use for the treatment of diseases. Key words: Dialium guineense, antimicrobial activity, phytochemical screening, microbial isolates, fruit pulp.
Highlights
Medicinal plants have been used for centuries as remedies for human diseases and offer a new source of biologically active chemical compounds as antimicrobial agent
After and before the antimicrobial sensitivity assay, these isolates were sub-cultured into Nutrient broth at 37°C (C. albicans in Potato Dextrose Agar (PDA) broth) overnight to ensure that the organisms were at their exponential phase of growth before carrying out the sensitivity analysis (Abah and Egwari, 2011)
The extracts of D. guineense fruit pulp showed antimicrobial activity against S. aureus, E. coli, K. pneumonia, P. mirabilis, P. aeruginosa and C. albicans with the exception of n-hexane extract showing no zone of inhibition to any of the isolates after the antimicrobial sensitivity assay was repeated twice
Summary
Medicinal plants have been used for centuries as remedies for human diseases and offer a new source of biologically active chemical compounds as antimicrobial agent. Plants have limitless ability to synthesize aromatic secondary metabolites, most of which are phenols or their oxygen-substituted derivatives (Geissman, 1963) Important subclasses in this group of compounds include phenols, phenolic acids, quinones, flavones, flavonoids, flavonols, tannins and coumarins. Scientists from divergent fields are investigating plants with a new age for their antimicrobial usefulness and as an alternative source to existing drugs. Plants with their wide variety of chemical constituents offer a promising source of new antimicrobial agent with general as well as specific activity (Nair and Chanda, 2007). The substances that can either inhibit the growth of pathogens or kill them and have no or least toxicity to host cells are considered candidates for developing new antimicrobial drugs (Iqbal and Arina, 2001)
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