Effect of Ascorbic Acid on the Formation of N-Nitrosodimethylamine in vitro

Abstract

Studies were undertaken to elucidate the effect of added L-ascorbic acid (AH₂) on the formation of N-nitrosodimethylamine (NDMA) in vitro. Results obtained may be summarized as follows:
1. When AH₂ was added to the reaction mixture (NaNO₂, 30mM+DMA, 10mM) at pH 6.0, the formation of NDMA was markedly blocked by more than 15 mM of AH₂. It is to be noted that the presence of 1 to 3 mM of AH₂ apparently enhanced the formation of NDMA regardless of reaction temperatures ranging from 0° to 80°C.
2. AH₂ blockage of NDMA formation occurred more conspicuously under acidic conditions (pH 1.1 to 6.0), and the maximum inhibition rate was recorded at pH 3.6 where the highest NDMA formation was observable in the reaction mixture without AH₂. The higher the AH₂ concentration, the greater was the blockage observed in reaction mixtures at varying pH values.
3. One possible mechanism has been discussed with regard to decreases in NO₂-, and ionization rates of HNO₂ and DMA to explain the inhibition or enhancement of NDMA formation occurring at pH 6.0 in the presence of varying amounts of AH₂.