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Parkinson's disease (PD) is one of the most common neurodegenerative diseases (NDD) and mainly affects the ageing population. A significant feature of PD pathogenesis is the progressive loss of dopaminergic neurons in the substantia nigra pars compacta part of the midbrain in affected persons. This neuronal loss occurs partly due to the increased generation of reactive oxygen species (ROS) in the mitochondrial and the depletion of adenosine triphosphate (ATP) in affected neurons. In this study, the methanolic extracts of Clivia miniata (CME) and Nerine humilis (NHE) belonging to the plant family Amaryllidaceae, were investigated for their neuroprotective potential in MPP+-induced neurotoxicity in SH-SY5Y neuroblastoma cells. Cell viability was determined using the 3-(4,5-dimethyithiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays and cell morphology was analysed using light microscopy. Furthermore, the effects of the extracts on apoptosis and ATP production were investigated using caspase 3/7 apoptosis kit and the Promega Mitochondrial ToxGlo ATP assay kit respectively. Additionally, the antioxidant contents of extracts were evaluated using routine laboratory procedures. The results show that pre-treatment of cells with the extracts at 2 and 4 μg/mL concentrations improved cell viability as well as cell morphology by inhibiting the toxicity induced by MPP+. The extracts also improved ATP levels in cells and attenuated the apoptosis induced by MPP+. Furthermore, antioxidant assays showed that both extracts had low antioxidant activity. Findings from this study indicate that CME and NHE may be promising as neuroprotective agents for PD and warrant further investigation to determine the bioactive components of the plants that may be responsible for the observed effects.

Malignant primary brain tumours are reported to be the leading cause of death from solid tumours in children and the third leading cause of death from cancer in adolescents and adults. Current treatment options include surgery, radiation and chemotherapy. Despite these treatment options, patient survival still remains poor. The Amaryllidaceae family contains alkaloids which have shown several biological activities including the treatment of Alzheimer's disease. This study investigates the cytotoxic activity of the methanolic extracts of fourteen plants belonging to the Amaryllidaceae family in brain tumour cell lines. The MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) cell viability assay was used to determine the effects of plant extracts on cell viability while routine antioxidant assays were conducted to determine the antioxidant activities of the extracts. Results showed that of the fourteen extracts, five (Cyrtanthus breviflorus, Amaryllis belladonna, Crinum variabile, Haemanthus pubescens, Nerine filifolia) showed cytotoxicity in all the cell lines tested with IC50 values under 100 µg/mL. Six extracts (Crinum moorei, Clivia miniata, Haemanthus amarylloides, Crossyne guttata, Nerine humilis, and Ammocharis longifolia) showed varying levels of cytotoxicity in the cell lines tested and were unable to induce 50% reduction in cell viability across the cell lines tested at the highest concentration of 100 µg/mL. Furthermore, three plant extracts (Brunsvigia bosmaniae, Boophone disticha, Strumaria truncata) had minimal or no cytotoxic effects on all cell lines tested when compared to control. The extracts also showed varying degrees of antioxidant activity but were not as potent as the positive control. Findings from this study suggest that species of the Amaryllidaceae family may be useful sources of phytochemicals for the treatment of central nervous system cancers and should be further explored in animal models of central nervous system (CNS) and other cancer types.