Browsing by Author "Ochieno, Dennis"

Now showing 1 - 2 of 2

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.
Spatial modeling of sorghum (sorghum bicolor) growing areasin Kenyan arid and semi-arid lands
(Elixirpublishers : Agriculture, 2014-01-10) Kigen, Charles; Ochieno, Dennis; Muoma, John; Shivoga, William; Konje, Martha; Onyando, Zedekiah; Soi, Benard; Makindi, Stanley; Kisoyan, Philip; Mironga, John
Sorghum (Sorghum bicolor) is an important African cereal crop and is listed among Africa’s lost crops but is now gaining popularity as other cereals are declining in production due to climatic change. To promote food security, many researchers and policy makers are shifting the focus on production of sorghum. In Kenya, sorghum is primarily grown in ASALs whose suitability is climatic factors but the extent is not known. This paper modeled the potential sorghum suitable areas of current and the years 2050 and 2080 climatic periods. The sorghum location data were downloaded from GENESYS and Kenya Agricultural Research Institute while climate data was from world climate database website. Analysis was done using Maxent and DIVA-GIS softwares. The model generated an excellent AUC of 0.97 and the suitable areas in the future are shown to expand in both 2050 and 2080 climatic periods though not in same magnitude. The main variables contributing more than 10 % of change in suitability areas in decreasing order are precipitation of wettest period, temperature seasonality (STD * 100), precipitation of warmest quarter, and precipitation of driest month. The generated information will guide the policy makers and stakeholders in making informed decisions with regard to the efforts of re-introduction and promotion of sorghum production in ASALs.