Aims: To determine chemical constituents of the Leaf extracts of Centella asiatica using the LC-MS and GC-MS and their antimicrobial activities. Study Design: Structural determination of compounds from the leaf extracts was done using GC-MS and LC-MS analysis. The antimicrobial properties of the extracts were done using disc diffusion method. Place and Duration of Study: Pure and Applied Chemistry Department, Masinde Muliro University of Science and Technology, Kenya: Between 2016-2019. Methodology: Plant materials of C. asiatica were sequentially extracted separately based on the polarity viz., hexane, ethyl acetate and methanol. Determination of chemical constituents was done using LC-MS and GC-MS analysis and phytochemical screening. The extracts were assayed against Staphylococcus aureus, Klebsiella pneumonia, Escherichia coli and Candida albicans. Standard antimicrobials viz. ampicillin and Nystatin were used as the control. Disc diffusion method was used and zones of inhibition, after respective incubation periods, were used to quantify antibacterial and antifungal activity. Results: Phytochemical screening of the hexane, ethyl acetate and methanolic extracts showed that terpenoids, flavonoids, saponins, alkaloids, steroids, amino acids and proteins, reducing sugars and carbohydrates were present. LC-MS and GC-MS analyses of the methanolic extracts identified 22 and 33 compounds, respectively, by use of the national institute of standards and technology (NIST) library. The extracts showed appreciable activity against common microbes tested. Conclusion: This study forms the basis for the biological characterization and significance of the compounds identified in the leaf and stem extracts of C. asiatica. These compounds are known to possess antibacterial and antifungal activities that could be established as potential candidates for future drug development. However, these extracts, need to be subjected to further chromatographic procedures to isolate the identified compounds and their bioactivities determined.
Aims: To determine the chemical composition and antibacterial activity of Kenyan Ganoderma lucidum. Study Design: Structural determination of the isolated compound was done using spectral evidences and in comparison with literature. The antibacterial properties of the compound was done using disc diffusion method. Place and Duration of Study: Department of Pure and Applied Chemistry, Masinde Muliro University of Science and Technology, between January and November, 2019. Methodology: Sequential extraction of dried samples of Kenyan G. lucidum were done using solvents hexane, ethyl acetate and methanol. Chromatographic separation of hexane extract of Ganoderma lucidum was done using spectroscopic data. The compound was assayed against Escherichia coli, Klebsiella pneumoniae, Methicillin–Resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Streptococcus pyogenes. Standard antibiotic namely; ampicillin was used as the control. Disc diffusion method was used and zones of inhibition, after respective incubation periods, were used to quantify antibacterial activity. Results: From hexane extract of Ganoderma lucidum, Ergosta-5, 7, 22-triene-3β, 14α – diol (22Z) was isolated. Ethylacetate and methanol extracts produced a mixture of complex compounds. Ergosta-5,7,22-triene-3β,14α-diol (22Z) exhibited significant activity against Methicillin-Resistance Staphylococcus aureus (MRSA) (p=0.022) and Streptococcus pyogenes (p = 0.05). The most sensitive microbe was Streptococcus pyogenes. Conclusion: One major compound, Ergosta-5, 7, 22-triene-3β, 14α – diol (22Z) was isolated, characterized and antibacterial activity determined.
One of the serious problems the world is facing today is the antimicrobial resistance on available antibiotics by most bacterial pathogens and the rising cost of finding effective antimicrobial agents. In recent years, efforts to find new drugs especially from natural sources have been boosted by the demand for an effective cure for infectious diseases. Only the antibacterial activity of apis mellifera honey and not stingless bee honey from western Kenya has been reported.
S TUDIES have demonstrated high levels of ampicillin resistance among Escherichia coli occurring in wastewater and environmental systems in western Kenya. The current study investigated antimicrobial resistance profiles and biofilm formation abilities in presence and absence of sub-lethal ampicillin concentrations, of E. coli recovered from final sedimentation ponds of two wastewater treatment plants in Kakamega municipality. 34 non-duplicate E. coli isolates were recovered by direct plating of wastewater sample aliquots on MacConkey agar and their biofilm formation capabilities measured by crystal violet assay while disc diffusion and Polymerase Chain Reaction (PCR) techniques were used to determine their antibiotic resistance levels and ampicillin resistance genes respectively. The Spearman's Chi-square test at P≤ 0.05 was used to check for interdependence between antimicrobial resistance and biofilm formation capabilities. 58.8% of the isolates were multi-drug resistant (MDR) and 85.3% showed resistance to ampicillin, which was found to be encoded by bla TEM in 65% and bla SHV in 8.8%. The biofilm phenotype was exhibited by 61.8% of all the isolates, amongst which 23.6% showed a strong, 14.7% a moderate and 23.6% a weak propensity to form biofilms. This study revealed lack of association between antibiotic resistance and biofilm formation, but interestingly, ampicillin concentration of 8.0µg/ml triggered the highest biofilm biomass among the isolates. The findings drive at the conclusion that biofilm production among E. coli in wastewater treatment plants(WWTPs) does not correlate with antibiotic resistance, but may be an important protection mechanism against sub-lethal antimicrobial levels present in environmental milieu.
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