Cytotoxic effect of P. noctiluca crude venom and fractions (F1 –F4) on U87 cells. Cells were treated with venom and its fractions at the indicated concentrations for 24 h. Cell viability was determined using the MTT assay and expressed as percentages of control which was exposed to vehicle only. Control value was taken as 100%. Data are expressed as the mean ± S.E. *p < 0.05 compared with control (untreated cells).