Repellency and Toxicity of Commiphora Africana Resin Extract and It’s Constituents against Cimex Lectularius and Characterization of its Active Constituents

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dc.contributor.advisorMargaret Mwihaki Ng’ang’aen_US
dc.contributor.advisorAhmed Hassanalien_US
dc.contributor.authorWairagu, Norman Wachira
dc.date.accessioned2022-08-31T09:14:52Z
dc.date.available2022-08-31T09:14:52Z
dc.date.issued2022
dc.descriptionA Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science (Analytical Chemistry) in the School of Pure and Applied Sciences of Kenyatta University, December, 2021en_US
dc.description.abstractBedbugs (Cimex lectularius Linnaeus) pose a great menace in many homes, hotels, public transport and institutions where they obtain blood meal from humans, chicken and domesticated animals. They cause physical and mental problems to the affected humans, on heavy and frequent feeding on the host leading to anemia. Bedbug control has not been successful due to their resistance to conventional insecticides, environmental pollution of the insecticides and the high costs involved. There is need to explore natural herbal-based insect control phytochemicals in control methods due to their environmental friendliness as compared to synthetic pesticides. Commiphora africana (A. Rich.) Engl. resin has been used traditionally to control blood-feeding insects and other arthropods such as lice, bedbugs, fleas, honey beetles and ticks. This research sought to extract bioactive compound(s) from C. africana resin, evaluate the repellency and toxicity of the extracts/compounds/selected blends against bedbugs. The isolated compounds were characterized using conventional spectroscopic techniques. The resin was tapped from the stem of mature C. africana trees in their natural habitat. The plant resin was extracted with H2O and in a separate set up sequentially extracted with CH3(CH2)4CH3, CH2Cl2, EtOAc and MeOH. The extracts were evaluated for insecticidal activity against C. lectularius. The CH2Cl2 crude extract proved to be the most effective against bedbugs with mean repellency of 98.5% and LC50 of 4.96 mg/L after 24- and 72- hrs exposure respectively. The extract was subjected to chromatographic separation and purification where the eluents (fractions) were evaluated at different doses for repellency and toxicity against bedbugs. The most active chromatographic fraction against bedbugs was analyzed by Gas Chromatography Mass Spectrometry (GC-MS) and identified 20 compounds in the class of esters, carboxylic acids, alkanes, alkenes, heterocyclics, aromatics, alcohols, amine and alkyne. Among the identified compounds, cedrol and citronellyl formate had significantly (p < 0.05) higher mean repellency (80.5% and 77.0% respectively after six hours of exposure) and toxicity (27.43 and 37.01 mg/L respectively after 24 hours exposure) against bedbugs than the rest. Selected blends of these compounds showed synergistic repellency and toxicity effects as compared to individual compounds. A six-constituent blend comprising of 9-octadecenoic acid, ethyl ester + octadecadien-1-ol + citronellyl formate + cedrol + hexadecanoic acid + 1,2-dihydro-6-methoxy-Naphthalene had the highest mean repellency (93.4 ± 6.61 % after 12 hours exposure) and toxicity (8.83 mg/L after 72 hours exposure) against bedbugs. The isolation of compounds from the CH2Cl2 resin crude extract gave five triterpenoid compounds (taraxasterol, pseudo-taraxasterol, beta-sitosterol, fungisterol and guggulsterol) which were characterized by conventional spectroscopic techniques and evaluated for repellency and toxicity against bedbugs. Fungisterol showed highest mean repellency (100%) and toxicity (14.40 mg/L) after 12 and 72 hours of exposure respectively. This study proves that the resin of C. africana contains compounds that can be used as an insecticide in bedbug control.en_US
dc.description.sponsorshipKenyatta Universityen_US
dc.identifier.urihttp://ir-library.ku.ac.ke/handle/123456789/24109
dc.language.isoenen_US
dc.publisherKenyatta Universityen_US
dc.subjectRepellency and Toxicityen_US
dc.subjectCommiphora Africana Resinen_US
dc.subjectExtracten_US
dc.subjectConstituentsen_US
dc.subjectCimex Lectulariusen_US
dc.subjectCharacterizationen_US
dc.subjectActive Constituentsen_US
dc.titleRepellency and Toxicity of Commiphora Africana Resin Extract and It’s Constituents against Cimex Lectularius and Characterization of its Active Constituentsen_US
dc.typeThesisen_US
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