Abstract:
Background and Objectives: Angiogenesis is the process of forming new capillary vessels from existing ones. This process is implicated in tumour growth, metastasis and wound healing. During tumour metastasis, angiogenesis is amplified as new capillaries are needed for cancer to spread. However, when this process is inhibited, wound healing is impaired. Cyclooxygenase-2 (COX-2), nitric oxide synthase (NOS) and lipoxygenase (LOX) are some of the enzymes that are highly expressed during angiogenesis and therefore provide a useful way to detect angiogenesis. Some medicinal plants have shown to possess angiogenetic-modulating properties, which has led to the development of anti-angiogenic drugs for the treatment of cancer. Spirostachys africana sond has been used historically to treat open wounds, ulcers and cancer. Nevertheless, its mechanism of action is still unclear. The aim of this study was to determine mechanisms of anticancer and wound healing activities of S. africana by evaluating its effects on the proliferation of MCF-7 cells and on the activities of COX-2, LOX and NOS. Materials and Methods: The dried plant materials were extracted with water and sequentially with organic solvents in their order of increasing polarity. Extracts were screened for cell growth inhibitory activity against breast cancer MCF-7 cells and for selectivity against normal breast MCF-10A cells. Extracts that showed growth inhibitory activity with IC50 values <10 μg mL–1 were further evaluated for effects on COX-2, LOX and NOS enzymatic activity. Results: The non-polar extracts of all plant parts had anti-proliferation activity with IC50 of 10 μg mL–1 or lower. All the leaf extracts showed selectivity for MCF-7 breast cancer. The selected extracts also induced NOS activity and inhibited LOX and COX-2 activity in a concentration dependent manner. Conclusion: It was concluded that the selected extracts may suppress angiogenesis by inhibiting COX-2 and LOX and induce apoptosis by increasing NOS activity. Spirostachys africana was found to contain tannins, glycosides, saponins and alkaloids which could be responsible for the biological activity observed.
