Influence of fruit and vegetable juices on the endogenous formation of N-nitrosoproline and N-nitrosothiazolidine-4-carboxylic acid in humans on controlled diets

Abstract

Water, green pepper, pineapple, tomato, strawberry, carrot, and celery juices were made 46 mg/100 ml in ascorbic acid by the addition of distilled water or ascorbate. The ability of each juice to inhibit endogenous formation of N-nitrosoamino acids (NAA) in humans was determined in controlled experiments. Sixteen men consumed a standard diet low in nitrate and ascorbic acid for 18 consecutive days. Nitrate (5.24 mmol) and L-proline (4.35 mmol) were given orally on days 3, 5, 7, 9, 11, 13, 15, 17 and 18. On days 3 and 18, L-proline was immediately followed by 100 ml distilled water (positive control). On days 5, 7, 9, 11, 13, 15 and 17, L-proline was immediately followed by 100 ml juice or 46 mg ascorbate in 100 ml distilled water (treatment). Only diet was given in between dosing days to ensure baseline levels of NAA excretion. Urine was collected for 24 h following treatments and analyzed for NAA. Green pepper, pineapple, tomato, strawberry and carrot treatments significantly inhibited N-nitrosoproline (NPRO) formation relative to the positive control. Also, green pepper, pineapple and tomato juices significantly inhibited NPRO formation relative to ascorbic acid alone. Green pepper significantly inhibited N-nitrosothiazolidine-carboxylic acid formation relative to ascorbic acid alone. These data demonstrate that green pepper, tomato, pineapple, strawberry and carrot juice have greater ability to inhibit endogenous nitrosation than would be expected based solely on their ascorbate content.

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

“…mechanisms responsible for their anticancer properties are not fully understood. Tomatoes, green peppers, pineapples, strawberries, and carrot juice all had a greater ability to inhibit endogenous nitrosation in vivo than an equal amount of ascorbic acid taken with water alone (Helser et al, 1992). Therefore, it seems possible that also phenolic compounds in strawberries might inhibit nitrosation.…”

“…Chemical catalysts, such as thiocyanate, and inhibitors, such as ascorbic acid, -tocopherol, allyl sulfur compounds and phenolic compounds, inXuence the endogenous formation of NOCs (Bartsch, Ohshima, & Pignatelli, 1988;Chung, Lee, & Sung, 2002;Helser, Hotchkiss, & Roe, 1992;Kurechi, Kikugawa, & Fukuda, 1980;Mirvish, 1986;Shenoy & Choughuley, 1992;Wu, Wang, Li, & Han, 1993;Xu, Song, & Reed, 1993).…”

Criteria and Recommendations for Vitamin C Intake

“…64 Nitrosamines are formed in the gastrointestinal tract under certain conditions and can be harmful. Nitrosamine formation may be decreased by vitamin C doses of 200 mg/d, 67 but whether this has clinical benefit remains to be determined.…”

“…Vitamin C transport will achieve V max in tissues, 61 LDL oxidation might be decreased compared with lower doses, 6,7 ascorbate recycling as a protective mechanism in neutrophils might be optimized, 64 and decreased nitrosation in the gastrointestinal tract might result from this dose. 67 Also, intake of 5 servings of fruits and vegetables is associated with decreased cancer risk. 14,69 Finally, 200 mg of vitamin C will prevent deficiency for more than 1 month if ingestion suddenly ceased.…”

Polyphenol Composition and Antioxidant Activity of Different Potentially Functional Kale-Based Snacks

“…Vegetable products are a good source of many biologically active antioxidant compounds [18]. Phenolic compounds, present in high concentration in human foods and beverages from plant and fruits, are potent blocking agents of N-nitrosamine compound formation [19]. Phytophenolics can exhibit a positive effect in disease prevention, playing a crucial role in many mechanisms related to cell differentiation, inhibition of N-nitrosamine formation [20], deactivation of pro-carcinogens [21], and maintenance of DNA repair [22].…”