Abstract

An extract of Fusarium verticillioides (Sacc.) Nirenberg culture isolated from rice in Niger State, Nigeria, previously found to be acutely toxic to mice and chicks was established to contain 8.233 ppm of total fumonisins (FBs). The present work was undertaken to evaluate the in vitro cytotoxic effect to human lymphocytes of the same 4-year old extract via flow cytometry over a 3 h period in comparison with those of aflatoxin B₁ (AFB₁), ochratoxin A (OTA) and fumonisin B₁ (FB₁) and to further elucidate the mycotoxins in extract using thin layer (TLC), column (CC) and high performance liquid chromatographic (HPLC) techniques. The efficiencies of different solvents for extraction of FBs were also determined. A dose-dependent response was obtained for all toxins tested via cytotoxicity assay. At concentrations of 25, 50 and 100 µg/ml, OTA was more toxic than AFB₁ followed by the extract which was comparatively as toxic as FB_1. Cytotoxicity data also revealed that, apoptosis is the major form of cell death induced by the tested mycotoxins and extract. Fumonisins B₁ (FB₁), B₂ (FB₂) and B₃ (FB₃) were found in the fungal extract at concentrations of 16.302, 6.423 and 2.456 ppm, respectively. The results also demonstrated that FBs are not extractible in hexane, benzene, diethyl ether and ethyl acetate, very low amount of the toxins can be recovered using dichloromethane (5 to 7%) and acetone (<10%), while methanol, acetonitrile and their aqueous solutions (32 to 87%) were found to be the best FBs extraction solvents.

Key words: Cytotoxicity, human lymphocytes, fumonisins, rice, Nigeria.