Browsing by Author "Osogo, Aggrey"

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Antimicrobial Coumarins from the Oyster Culinary-Medicinal Mushroom, Pleurotus ostreatus (Agaricomycetes), from Kenya
(International Journal of Medicinal Mushrooms, 2016-01-01) Baraza, Lilechi D.; Wekesa, Wekesa; Korir, Cheruiyot Jackson; Juma, Fredrick B.; Ochieno, Dennis; Wairimu, Kamau R.; Osogo, Aggrey; Heydenreich, Matthias
Pleurotus ostreatus has been widely used as food because of its nutritional and medicinal properties. These have been attributed to the presence of macronutrients, minerals, vitamins, and amino acids, among other secondary metabolites. There are, however, few reports on the antimicrobial activities of different classes of purified compounds from P. ostreatus. This led to the current study, the objective of which was to chemically characterize the antibiotic activities of P. ostreatus against selected human pathogenic bacteria and endophytic fungi. Chemical structures were determined using spectroscopic methods and by comparison with values of related structures reported in the literature. Pure compounds from P. ostreatus were tested in vitro against pathogenic bacteria (Staphylococcus aureus and Escherichia coli) and endophytic fungi (Pencillium digitatum and Fusarium proliferatum). A new compound, (E)-5,7-dimethoxy-6-(3-methylbuta-1,3-dienyl)-2H-chromen-2-one (5-methoxy-(E)-suberodiene) (compound 2), along with ergosterol (compound 1) and 5,7-dimethoxy-6-(3-methylbut-2-enyl)-2H-chromen-2-one (toddaculin; compound 3), were isolated from the fruiting bodies of P. ostreatus. The growth of S. aureus, F. proliferatum, and P. digitatum colonies was inhibited in media containing compound 2, with minimum inhibitory concentrations closely comparable to those of conventional antibiotics.
Biodegradation of carbofuran in soils within Nzoia River Basin, Kenya
(Journal of Environmental Science and Health, 2015-04-06) Onunga, Daniel O.; Owino, Isaac; Ngigi, Anastacia; Osogo, Aggrey; Orata, Francis; Getenga, Zachary; were, Hassan
Carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) has been used within the Nzoia River Basin (NRB), especially in Bunyala Rice Irrigation Schemes, in Kenya for the control of pests. In this study, the capacity of native bacteria to degrade carbofuran in soils from NRB was investigated. A gram positive, rod-shaped bacteria capable of degrading carbofuran was isolated through liquid cultures with carbofuran as the only carbon and nitrogen source. The isolate degraded 98% of 100-μg mL−1 carbofuran within 10 days with the formation of carbofuran phenol as the only detectable metabolite. The degradation of carbofuran was followed by measuring its residues in liquid cultures using high performance liquid chromatography (HPLC). Physical and morphological characteristics as well as molecular characterization confirmed the bacterial isolate to be a member of Bacillus species. The results indicate that this strain of Bacillus sp. could be considered as Bacillus cereus or Bacillus thuringiensis with a bootstrap value of 100% similar to the 16S rRNA gene sequences. The biodegradation capability of the native strains in this study indicates that they have great potential for application in bioremediation of carbofuran-contaminated soil sites.
Distribution and Occurrence Viruses infecting Common Bean (Phaseolus vulgaris L) in Western Kenya
(KIBU, 2019-06-13) Osogo, Aggrey; Were, Mariam; Muyekho, Francis; Were, Hassan
Common bean (Phaseolus vulgaris L) is the most widely grown pulse and a major food security crop in East Africa, including Kenya. It is the main source of protein and starch for over 300 million people in East Africa and Latin America. Despite the enormous importance of beans to East Africans, bean production in Kenya remains relatively low with an average yield of 585 Kg/ha compared to Ethiopia and Rwanda with yield of 1888 kg/ha and 913 kg/ha respectively. In Kenya including Western Kenya, bean productivity is declining due to several biotic and abiotic constraintsincluding several viral diseases.Management of these viral diseases requires information on types, distribution, incidence, occurrence and severity, which is currently limited.It has been reported that the most important viruses of common bean in Kenya are Bean common mosaic virus (BCMV) and Bean common mosaic necrosis virus (BCMNV) though other viruses have been documented and known to exist. There is inadequate information about the occurrence and distribution of these viruses in Western Kenya which makes management of these diseases difficult. This study was therefore commissioned to document the different types of viruses infecting beans crop and determine their incidence and severity through a comprehensive disease diagnostic survey. Results showed that the average viral disease incidence per county was Nandi (42.8%), Kakamega (29.3%), Vihiga (12%) and Bungoma (9%). Additionally, viral disease severity Nandi (42.8%), Kakamega (29.3%), Vihiga (12%) and Bungoma (9%). The most dominant virus which occurred in all the counties surveyed was Bean Golden Mosaic Virus (BGMV) with disease incidence of 100%. Bean Yellow Mosaic Virus (BYMV) was detected in leaf samples from Vihiga County. These results seem to indicate that BGMV could be upstaging BCMV and BCMNV in the region. The increased knowledge of common bean virus diseases in Western Kenya is expected to result into informeddevelopment of strategies for management of the diseases and thus increased production, which in turnhas implications on nutrition and income.