Rapid Bioassay-Guided Screening of Natural Products Derived from Cytotoxic Oils

It has been consistently reported that canola oil has life shortening effects in Stroke-Prone Spontaneously Hypertensive Rats (SHRSP) and this effect is not due to the fatty acid composition of the oil; it is possible that the phytosterol content and the types of phytosterols might play some role in the life shortening effect though this is still not completely resolved. The conventional approach to screen toxic substances in oil using rat models takes more than six months and involves a large number of animals. In this report we explain a rapid bioassay-guided elucidatation of bioactive substances in oils and/or natural product extracts using human cell lines in place of animal models. Non-polar and polar fractions of canola, olive and soybean oil were obtained by column chromatography. Human kidney cell lines; NRK 52E and HEK 293T were treated with un-fractionated oil, non-polar or polar fractions at the concentration of 150–1800µg/ml. Cytotoxicity of the oils and oil fractions were determined by measuring cell viability. Treatment of kidney cells with polar fraction of canola oil that represented 3.7% of total canola oil showed decreased cell viability (lc₅₀=650µg/ml) compared that of with polar fraction of soy (lc₅₀=1420µg/ml) and olive (lc₅₀=1330µg/ml) oil. The un-fractionated and non-polar fraction of canola oil that represented 93.6% of oil showed higher cell viability than polar fraction of canola oil with the comparable cell viability of the respective fractions of soy and olive oil. The cytotoxicity bioassay employed in the current project needs only two weeks to test multiple fractions compared to six months per fraction in animal experiments. Fractionation of mixtures before bio-assay enhances the effectiveness of the detection of active compounds as fractionation increases the relative concentrations of minor components. The non-polar fraction, which represents the majority of the lipids in canola oil, appears to be safe compared with polar fraction containing mostly phyto-compounds in canola oil. Acknowledgements: We thank the Deakin University, Victoria, Australia for the award of Alfred Deakin Fellowship and financial support.