The human population can be considered as a subject of combined exposure to chemicals against which the gastrointestinal tract represents the first barrier. The most relevant are those compounds that occur in plants which are used as foods, medicines and beverages. Of special interest are the mycotoxins deoxynivalenol (DON) and fumonisin B1 (FB1), two of the most commonly encountered food-borne mycotoxins and curcumin, a popular spice and pigment reported to have antineoplastic properties. In this study, the HT-29 cell line was used to assess the toxicity of the mycotoxins DON and FB1 (5uM and 50uM) as well as the possible cytoprotective effects of curcumin (50uM) on colonic cells. Mixtures of both mycotoxins were also assessed to determine any possible interaction. Cytotoxicity, DNA fragmentation, cellular morphology and cell surface alterations were evaluated using the methylthiazol tetrazolium (MTT) bioassay, the single cell gel electrophoresis (SCGE) assay, fluorescence microscopy and scanning electron microscopy respectively. Deoxynivalenol displayed cytotoxic and genotoxic effects as well as induced morphological features of apoptosis and cell surface alterations that worsened with increasing concentration. Fumonisin B1 exhibited a proliferative effect at the high concentration however DNA damage and cell surface alterations worsened with decreasing concentration. Mixtures of DON and FB1 displayed similar effects to those exhibited by DON in terms of cytotoxicity, DNA fragmentation, morphology and cell surface alterations indicating that DON is able to antagonise the effects of FB1 at the concentrations tested. Curcumin appeared to exhibit a protective effect that was prominent when co-administered with the 50uM toxin concentration. Low concentrations of DON and FB1 (5uM) were sufficient to induce apoptosis in this cell line and suggest a danger from natural contamination by these toxins. Curcumin, however, warrants further investigation with regards to its cytoprotective activities in the presence of these mycotoxins as it could present a promising candidate for a natural chemoprotective agent in the armamentarium against mycotoxin induced cancers. / Thesis (M.Med.Sc.)-University of KwaZulu-Natal, 2005.