Protective effect of broccoli, onion, carrot and licorice extracts against cytotoxicity of N-nitrosamines evaluated by 5 bromo-2′-deoxy-uridine (BrdU) assay and determination of total cellular DNA content.

The protective effect of nine fruit and vegetable aqueous (H 2 O) and ethanolic (EtOH) extracts against cytotoxicity of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosodibuthylamine (NDBA) and N-nitrosopiperidine (NPIP) was evaluated by 5-bromo-2'-deoxy-uridine (BrdU) assay and determination of total cellular DNA content. When BrdU assay has been used, two vegetable extracts exhibited a protective effect (to 100% of DNA synthesis) and a stimulation of cellular proliferation (> 100% of DNA synthesis) in decreasing order against NDMA and NPYR: onion H2O > carrot EtOH . Licorice H2O extract showed only a protective effect against NDBA and NPIP and broccoliEtOH extract exhibited a protective effect against all N-nitrdsamines tested at concentrations of 0.1 mg/ml. When determination of total cellular DNA content has been used, a significant protective effect and stimulation of cellular proliferation was found for three vegetable extracts against NDMA and four against NPYR. Decreasing order against NDMA and NPYR were, respectively, onion EtOH > broccoli EtOH > onion H2O > licorice H2O and onion EtOH > broccoli EtOH > onion H2O > carrot EtOH > licorice H2O With the concentrations used, a protective effect and stimulation of cellular proliferation was also found for broccoli EtOH and carrot EtOH extracts against NDBA and for carrot EtOH extract against NPIP.