INHIBITION OF N-NITROSATION OF SECONDARY-AMINES IN-VITRO BY TEA EXTRACTS AND CATECHINS

Inhibition of nitrite-mediated N-nitrosation of dimethylamine, morphol ine and N-methylaniline by tea extracts and by 6 individual catechins in the extracts was studied. The inhibitions were detected by quantify ing the nitrosamines formed. Eight different kinds of teas (5 green te as, a roasted green tea, an oolong tea, and a black tea) were examined for their inhibitory abilities and for their catechin contents, with an attempt to correlate the inhibitory activities to the catechin cont ents. The results showed that (1) the green tea extracts inhibit stron gly the N-nitrosation of the three secondary amines tested, (2) the 6 catechins, notably epigallocatechin, are capable of blocking the N-nit rosations very efficiently, even more efficiently than ascorbic acid, and (3) the inhibition activities of green tea extracts are mostly asc ribable to the catechins present in the extracts. These inhibitions oc cur by rapid reactions between nitrite and the catechins. It was obser ved that no mutagenicity results from the reaction between the tea ext racts and nitrite. (C) 1998 Elsevier Science B.V.