Faculty of Agriculture, Engineering and Natural Sciences
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Browsing Faculty of Agriculture, Engineering and Natural Sciences by Subject "Acetylcholinesterase inhibition"
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Item Investigation of neurotoxic principles of the Tumbleweed, Trachyandra Laxa, responsible for livestock losses in Southern Africa(University of Namibia, 2020) Van Wyk, Hedwig MaureenLivestock losses due to poisonous plants remain a major concern for livestock agriculture in southern Africa. However, for a number of such toxic plants, including Trachyandra laxa (family Xanthorrhoeaceae, sub-family Asphodeloideae), the toxic components are still unknown. Trachyandra laxa primarily affects the central nervous system when ingested by livestock, causing paralysis. Traditional bioactivity-guided fractionation approaches used for the isolation and identification of toxins are time consuming and laborious. Therefore, in this study, a chemical screening approach involving gas chromatography - mass spectrometry (GCMS) was used. The chemical constituents were extracted from the leaves, inflorescence, flowers, roots and rhizomes of T. laxa, using a sequential extraction approach with solvents of different polarity, starting with hexane and ending with methanol. Extracts were screened for cytotoxicity using the MTT-assay, for neurotoxicity using acetylcholinesterase (AChE) inhibition. Results showed no cytotoxicity and the acetylcholinesterase inhibition assay displayed positive results for the dichloromethane (DCM) extract, indicating neurotoxic activity. The chemical screening approach was subsequently pursued on the DCM extracts only. In this approach, the DCM extracts were analysed by GC - MS and their major volatile constituents were tentatively identified from their mass spectra and retention indices. A literature search was conducted to determine which of the tentatively identified compounds are toxic. This led to the discovery that two of the constituents, the α,β-unsaturated lactones, dihydroactinidiolide (DHA) and its hydroxylated analogue, are known to have potent AChE inhibition properties. It is envisaged that this study will pave the way to further research on specific treatment of animals affected by T. laxa poisoning or the development of a preventative agent that can be used to avoid T. laxa poisoning.Item Phytochemical analysis and acetylcholinesterase inhibition activity of medicinal plants used in the traditional treatment of mental disorders in Kavango east region of Namibia(University of Namibia, 2022) Nghilalulwa, Theodor Nande N.In Namibia, various plants are used in the treatment of various illnesses in traditional healing systems, however the majority of these plants have not been characterised in terms of chemical constituents, and therefore, their safety and efficacy are unknown. The present study focused on the phytochemical analysis and evaluation of the acetylcholinesterase (AChE) inhibition activity of the extracts of five medicinal plants (Laggera decurrens, Ficus glumosa, Psendolachnostylis maprounifolia, Ochna pulchra and Ozoroa longipes) used in the traditional treatment of mental disorders in Kavango east region. Extracts were prepared from the powdered roots and leaves of the plants using dichloromethane/methanol (50/50, %v/v) and ethanol. Extracts were screened for the presence of alkaloids, saponins, diterpenes and flavonoids using standard methods. Saponins, diterpenes and flavonoids were found to be present in all the extracts, except for the leaves of O. longipes, while no alkaloids were detected in any of the plant extracts. Diterpenes appeared to be the most abundant phytochemicals for most of the samples. Leaf extracts exhibited varying levels of AChE inhibition activity. The L. decurrens proved to be the most potent plant species with percentage inhibition ranging from 74–101% for the dichloromethane/methanol (DCM/MeOH) extract and 93–106% for the ethanol extract. The highest inhibition percentages were observed at concentrations of 200 and 100 µg/mL for the DCM/MeOH and ethanol extracts respectively. Compounds were be tentatively assigned to chemical classes based on their ultraviolet absorption spectra. Future studies should employ spectroscopic techniques such as mass spectroscopy (MS) and nuclear magnetic resonance (NMR) spectroscopy to identify the chemical compounds present in these extracts