Protective effect of broccoli, onion, carrot, and licorice extracts against cytotoxicity of N-nitrosamines evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay

The protective effect of nine fruit and vegetable aqueous (H2O) and ethanolic (EtOH) extracts against the cytotoxicity of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosodibutylamine (NDBA), and N-nitrosopiperidine (NPIP) was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The fruit extracts under investigation did not show a protective effect against any N-nitrosamines tested. Four vegetable extracts exhibited a protective effect (to 100% of survival) and a stimulation of cellular proliferation (> 100% of survival) in decreasing order against NDMA and NPYR: broccoli(EtOH) > onion(H2O) > carrot(EtOH) > onion(EtOH) > licorice(H2O). Decreasing orders against NDBA and NPIP were, respectively, broccoli(EtoH) > licorice(H2O) > carrot(EtoH) > onion(EtOH) and broccoli(EtOH) > carrot(EtOH) > licorice(H2O) > onion(EtOH). Thus, broccoli(EtOH) extract (19-20 mg/mL) showed greater protective effect and stimulation of cellular proliferation (160% of survival) against all N-nitrosamines studied than the other vegetable extracts tested.