N-nitrosamine inhibition by strawberry, garlic, kale, and the effects of nitrite-scavenging and N-nitrosamine formation by functional compounds in strawberry and garlic

High nitrate and amine-rich food intake may result in an increased risk of endogenous formation of carcinogenic N-nitroso compounds (NOCs). We studied the effects of whole strawberries, garlic and kale on the formation of N-nitrosodimethylamine (NDMA) in a traditional Korean diet (amine and nitrate-rich) in simulated saliva and gastric conditions. The addition of whole strawberries, kale and garlic juices in the diet reduced NDMA formation by amine and nitrate. Strawberries and garlic juice were more effective than kale. To identify active compound, isolated fractions were prepared from strawberries or garlic juice samples by preparative liquid chromatography. Inhibition of NDMA formation and nitrite-scavenging ability of each fraction (strawberries: S1-S4; garlic juice: Al-A5) was tested. Fraction A4 inhibited NDMA formation by 50.5 +/- 5.4% and increased the effect of nitrite-scavenging by 72.3 +/- 8.7%. Fractions A3 and A4 were identified as 1,2-benzendicarboxy acid (A3) and S-oxodially disulfide (A4) compounds by mass spectrophotometry and C-13 nuclear magnetic resonance. (c) 2006 Elsevier Ltd. All rights reserved.