Investigation of the bioactivity of an extract from Ricinus communis

Abstract

Cancer is a leading cause of death in the western world, ranking second only to cardiovascular disease. A number of drugs used in chemotherapy are derived from natural products, thus highlighting the importance of such compounds. An extract from the leaves of the castor oil plant, Ricinus communis, was obtained by steam distillation. The in vitro cytotoxicity of this extract was studied, on human tumour cell lines and peripheral blood mononuclear cells. The MTT cytotoxicity assay, which measures mitochondrial activity, was used to detect cell viability. A combination of techniques was used to monitor the biochemical and morphological changes characteristic of apoptosis, to investigate the mechanism by which Ricinus communis extract influences SK-MEL-28 melanoma cell growth. Staining with quinacrine dihydrochloride displayed changes in nuclear size and shape, chromatin condensation and fragmentation, and the formation of apoptotic bodies. Sub-diploid nuclei were revealed by flow cytometry. The expression of phosphatidyl sirene on the outer surface of the cell membrane, following double staining with propidium iodide and the annex in V -FITC antibody conjugate, was observed by fluorescence microscopy. Loss of mitochondrial memhrane potential, associated with the early stages of apoptosis, was demonstrated by flow cytometry. GC-MS chromatograms for the extract revealed that the principal constituents of the extract were compounds classified as terpenoids.

In conclusion, Ricinus communis extract is composed of a number of terpenoids, which are cytotoxic to a variety of human tumour cell types. They are capable of inducing apoptosis in SK-MEL-28 melanoma cells at low concentrations, while features of necrosis were observed at higher concentrations, as demonstrated by a number of experiments. The lack of a suitable therapeutic window, manifested by the cytotoxicity produced by the extract on PBMC, minimises the use of the whole extract in the clinical setting, nonetheless it might be a useful tool in further anti-cancer studies.