P20: Evaluation of generation of nitric oxide by reducing nitrite with antioxidants in drinks

Background Nitrate, contained in vegetables and also secreted as saliva, is known to be reduced to nitrite in the oral cavity. When nitrite is swallowed with antioxidants, nitrite is reduced to nitric oxide (NO) in gastric acidic conditions. In this study, NO generation in acidic conditions by reducing nitrite with antioxidants contained in drinks were evaluated. Methods Sample drinks were added to 50 mL of a citrate buffer solution (pH 2) containing sodium nitrite. Vegetable juice, tomato juice, green tea, coffee and red wine were used due to its healthy and antioxidative effects. Generated NO concentration was measured using an NO sensor (amiNO-700; Innovative Instruments). Nitrate and nitrite concentrations in various drinks were measured by a NOx analyzer (ENO-20; EICOM). Results Addition of each of the drinks to a nitrite-containing buffer solution induced generation of NO. Generated NO concentration varied depending on the kind and volume of drink added and concentration of nitrite added. Generated NO concentration was higher with green tea, coffee and red wine than vegetable juice and tomato juice. Green tea, coffee and red wine are rich in polyphenols of catechin, chlorogenic acid and tannin, respectively. These polyphenols are known for their strong reductive effects and thus may be also effective reducing substances for NO generation. Vegetable juice and tomato juice contains various vitamins, and tomato juice contains much lycopene as antioxidants; however, the reducing effect of these drinks is known to be smaller than that of drinks containing much polyphenols. It should be noted that green tea and red wine contain vitamin C and sulfite, respectively, as additional antioxidants. An additional experiment using vitamin C and sulfite as reducing substances instead of drinks shows that NO generated with green tea and red wine was mostly derived from the natural compounds in drinks. Conclusion Generation of NO by reducing nitrite with drinks containing antioxidants was evaluated in acidic conditions. Green tea, coffee and red wine generate higher levels of NO than vegetable juice and tomato juice. Polyphenols are thus demonstrated to be highly potential reducing substances for generating NO from nitrite in acidic conditions. Disclosure Nothing to disclose.