The anti-termite properties and basic phytochemicals of eight local plants and the chemical characterisation of thevetia peruviana (pers) k. schum in Ghana

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There is an increasing interest in the use natural products for termite control because of their environmental safety. Some local plant materials have been mentioned as potential alternatives to synthetic termiticides. The objective of this work was to determine the antitermitic efficacy of locally available plants such as; Thevetia peruviana (pers) K Shum Carapa procera DC, Jatropha curcus L ,Cassia nigricans Vahl, Cymbopogon ginganteus (Hachst) Chiov), Hyptis spicigera Lam., Vetiver zizaniodes Nash (vetiver grass) and Chromolaena odorata (L). Following the identification and collection of the experimental plants and termite samples, a series of field and laboratory experiments were conducted using parts of the plants to determine their antitermite efficacy. Antitermite efficacy was measured as their tolerance to termite damage, repellency and toxicity to termites. This was followed by extraction into petroleum ether, ethanol and water and the analysis of the most efficacious extract by chromatography (thin layer, column and high pressure) and spectrometry (mass spectrometry, nuclear magnetic resonance and infra red) methods to identify the active ingredients in the extract of the most efficacious plant. Resistance to termite destruction was measured by the loss in weight of stakes buried in treated and untreated soil and by visual assessment of extent of destruction. Repellency or attrantancy was determined by counting the number of termites that moved towards or away from filter paper pads treated with extracts of the test material. The results showed that soil treated with pulverised materials from T. peruviana offered the best protection to buried stakes against damage by subterranean termites. Field tests conducted with petroleum ether, ethanol and water extracts of T. peruviana suggested that the ethanol extract of T. peruviana resisted the destructive effects of termites most. In the repellency/attrantancy test, the ethanol extract was found to be an attractant. When the fractionated components of the ethanol extract were tested on brine shrimps, fraction 1 was found to be highly toxic suggesting obvious cytotoxicity. Analysis of fraction 1 by chromatography and spectrometry methods indicated the presence of two components digitoxin and digitoxigenin which were found to be toxic to brine shrimp. Sucrose was also isolated from the crude ethanolic extract of T. peruviana. Thus this work has shown that the potential for the use of anti-termite agents from T. peruviana is promising.
A thesis submitted to the Department of Chemistry, Kwame Nkrumah University of Science and Technology, Kumasi, in fulfilment of the requirements for the award of the Doctor Philosophy