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Methanolic and aqueous leaf extracts of Chrysophyllum albidum (African star apple) and Garcinia kola (bitter kola) were studied for in-vitro microbial activity using the disc diffusion technique. The aqueous and methanolic leaf extracts of Chrysophyllum albidum showed antimicrobial activity against Escherichia coli, Staphylococcus aureus and Candida albicans but showed no antibacterial activity against Klebsiella pneumonia. The methanolic leaf extract of Garcinia kola inhibited the growth of Escherichia coli, Staphylococcus aureus and Klebsiella pneumonia while the aqueous extract of the leaf inhibited the growth of Staphylococcus aureus and Escherichia coli. Both methanolic and aqueous leaf extracts of the plant showed no antifungal activity against Candida albicans. The minimum inhibitory concentrations of the leaf extracts of Chrysophyllum albidum ranged from 12.5 mgL-1 to 25 mgL-1 while those of Garcinia kola ranged from 25 mgL-1 to 50 mgL-1. The results obtained suggest that the leaves of these plants can be used in treating diseases caused by the test organisms. The further investigation on the crude extracts would characterize bioactive components of the leaves of Chrysophyllum albidum and Garcinia kola.

This study investigated the impacts of spent engine oil on the physicochemical properties of soil, soil's microbial population and growth of Capsicum annuum. It covered assessment of different levels of contamination (0, 20, 40, 60 and 80%) in soil; which represents the degree of oil spillage concentration on the growth performance of C. annuum investigated. Percentage germination, seedling height, number of leaves and number of branches decreased as the concentrations of the spent engine oil in soil samples increased and affected soil physicochemical properties. The screening experiment conducted showed that poultry manure improved the physicochemical properties of sandy loam soils contaminated engine oil. The effects of poultry manure as an organic amendment was assessed using pepper (C. annuum) as test crop. All amendment made significant increase in soil organic carbon and calcium content over the polluted soils. Soil acidity increased, soil exchangeable ions decreased. N, P and K were altered in the polluted soils as compared to the controls. There were increased bacterial counts (2.21 – 2.85) and a decrease in fungi population (0.48 - 0.59) in the spent engine oil-contaminated soils compared with the control. The oil reduced germination percentage, depressed growth, reduction in leaf number and plant height of the C. annuum. Therefore the spent engine oil clearly had detrimental effects on soil's physicochemical and biological properties. The oil contributed largely to the extreme acidic nature of the polluted soils. However, maximum increase in plant height, germination percentage, number of leaves and branches were recorded with amendment of the polluted soils with poultry manure. Results show the considerable potential of remediation protocols with poultry manure as a remediating agent for oil spill remediation in the soil samples.

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