Browsing by Author "Kipngeno, Chirchir Denis"

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Isolation and purification of mosquito larvicidal compounds from extracts of a basidiomycete jo5289
(Egerton University, 2010-02) Kipngeno, Chirchir Denis
Mosquitoes present a worldwide, public health and nuisance challenge since they transmit human diseases including west Nile virus, malaria, dengue, Japanese encephalitis, filiarisis and other viral diseases throughout the globe. An obvious method for preventing the spread of these diseases is to control mosquito vector population by insecticides and synthetic agents, which have been developed and employed in the field with considerable success. As a result of insects’ resistance and adverse non-target effects, the current trend is to reduce or eliminate many of these older insecticides and develop safer, biodegradable, low costs larvicides for vector control. The secondary metabolites from higher fungi were thus investigated for possible mosquito larvicidal activity to control mosquitoes. A basidiomycete serialized JO5289 was collected from undisturbed habitat in Londiani forest in Rift Valley province. The strain was preserved as agar slant and the corresponding herbarium material kept in a fungal culture collection in the Integrated Biotechnology Research Laboratory (IBRL) at Egerton University. On initial screening it was found to produce active compounds in liquid culture against Aedes aegypti larvae. It was cultured in sterile submerged nutrient liquid malt media and growth conditions were manipulated to trigger the generation of secondary metabolites. From the culture two sets of crude extracts were prepared with intracellular secondary metabolites prepared from mycelium (Mex) while extracellular secondary metabolites prepared from the cultured filtrate (Kex). The crude extracts were tested for larvicidal activities against late third instar larvae and early fourth instar larvae of Ae. Aegypti before activity guided purification of the active compounds was carried out. These afforded eleven purified compounds which were subjected to NMR experiments (both 1D and 2D), that were used to determine the chemical structures of the compounds. Two mosquito larvicidal compounds were purified; 4-(2-hydroxyethyl)phenol and 3-methoxy-5-methyl-1,2-benzenediol with LC50 values of 231 and 237ppm, respectively against Ae. aegypti larvae after 24 hours. The third compound that was purified 2-hydroxy-4-(4-hydroxychroman-7-yl)but-3-enal whose larvicidal activity was not determined due to low yield. These compounds (4-(2-hydroxyethyl)phenol and 3-methoxy-5- methyl-1,2-benzenediol) have been produced from cultures of a basidiomycete and reported to have mosquito larvicidal activity for the first time. Despite the limitations of necessary research equipment, the study has demonstrated the potential of a basidiomycete JO5289 as a source of mosquito larvicidal compounds. It is the recommendation of this work that these compounds can be evaluated further for product development.
Screening and characterization of some anticancer compounds from Salicaceae, Myrtaceae, Euphorbiaceae and Solanaceae families
(Egerton University, 2019-10) Kipngeno, Chirchir Denis
The chemistry of natural products is very important since it has been used in the search for bioactive compounds for management of various human diseases including cancer. The increase in the incidence of cancer coupled with the undesirable side effects observed with chemotherapic agents urges the discovery of new agents from natural sources. In this study the four ethnomedicinal plants; Dovyalis abyssinica (Salicaceae), Solanum mauense (Solanaceae), Syzigium guinense (Myrtaceae) and Croton dichogamous (Euphorbiaceae) were investigated for their unvalidated anticancer activities. Crude extracts for stem bark of S. guinense, fruits of S. mauense, and roots of both D. abbysinica and roots of C. dichogamous were prepared via cold extraction method. The crude extracts were purified by repeated column chromatography and Thin Layer Chromatography. This resulted in various pure compounds which were analysed by use of 1D NMR, 2D NMR spectroscopic techniques and MS spectrometry. The NMR spectral data obtained together with MS data were interpreted, the structures of the compounds elucidated and their chemical structures proposed. A total of twelve compounds were isolated, purified, their chemical structures proposed and four of these compounds were evaluated for their anticancer activity. Two previously reported compounds; β-sitosterol (47) and betulinic acid (21), were obtained from stem bark extracts of S. guinense as well as from the fruits extracts of S. mauense. Two previously reported compounds; Tremulacin (29) and Benzoic acid (48) were isolated from the roots extract of D. abyssinica. Eight compounds were isolated from roots extract of C. dichogamous; Acetyl aleuritolic acid (49), 3β,4β:15,16-diepoxy-13(16),14-ent-clerodadiene (50), 3β, 4β:15, 16-diepoxy-13(16), 14-ent-clerodadien-17,12S-olide (51), 15,16-epoxy-5, 13(16), 14-ent-halimatriene-3-ol (52), crotodichogamoin A (53), crotohaumanoxide (54), crotodichogamoin B (55) and Cadin-1(6),2,4,7,9-penta-ene (56). Selected compounds were evaluated for their anticancer activity by use of cancer cell lines. Betulinic acid (21) was screened against 57 cell lines and only 25 gave positive results. Acetyl aleuritolic acid (49), 15,16-epoxy-5,13(16),14-ent-halimatriene- 3-ol (52) and crotodichogamoin A (53) were also evaluated for their anticancer activity and and their one dose mean value percentage growth at 15 μg/ml were 97.86, 99.39 and 100.6, respectively. The mean values of growth inhibition of the three compounds tested against one dose NCI cell line panel did not meet the standards for further testing against the five-dose NCI cell line panel. The study recommends toxicological studies be done on the medicinal plants extracts to enhance their full exploitation.