Syringic acid ameliorates (L)-NAME-induced hypertension by reducing oxidative stress.

The objective of the present study was to investigate the effects of syringic acid (SA), a phenolic acid, on N(ω)-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats. Hypertension was induced in adult male albino rats by oral administration of L-NAME (40 mg/kg/day) dissolved in drinking water daily for 4 weeks. Rats were treated with different doses of SA (25, 50, and 100 mg/kg body weight (b.w.)). Systolic blood pressure of control and experimental rats was recorded. Plasma nitric oxide metabolites (NOx), lipid peroxidative products such as thiobarbituric acid reactive substances, lipid hydroperoxides, conjugated dienes, and antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, vitamin C, vitamin E, and reduced glutathione were estimated in erythrocytes, plasma, and tissues of experimental rats. Hepatic marker enzymes such as aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase and renal functional markers such as urea, uric acid, and creatinine were also estimated in serum. The increased levels of blood pressure, lipid peroxidation products, hepatic and renal function markers, and the decreased level of NOx and antioxidants in L-NAME-induced hypertensive rats were reversed upon SA treatment. The protective effect at the dose of the three tested doses (25, 50, and 100 mg/kg) of SA at a dose of 50 mg/kg b.w. exerts optimum protection. Biochemical findings are substantiated by the histological observation. The protective effects of SA are mediated by reducing oxidative stress and retaining the bioavailability of NO in the cardiovascular system.