Abstract:
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
