Cytotoxicity tests were done with the fibroblast cell line NCTC-929 cultured in minimal essential medium (MEM; Sigma). The culture medium was supplemented with 10% heat-inactivated FBS,100 U/mL penicillin G and 100 lg/mL streptomycin. The cultures were maintained at 37 C in a humid atmosphere with 5% CO2. Cell viability was assessed by the resazurin reduction assay (Rolónet al., 2006) with cells grown in 96-well microplates at a final concentration of 3 104 cells/well. After the culture medium was removed, 20 lL of 2 mM resazurin was added to each well with a final volume of 200 lL. The plates were incubated for 3 h andresazurin reduction was determined by absorbance readings at 490 and 595 nm. The blank control was subtracted and each concentration determined in triplicate.