Antioxidant effect of Piper nigrum on hepatocyte membrane and LDL oxidation and non-enzymatic glycosylation of hemoglobin

Free radicals especially reactive oxygen species can produce some disorders by damaging biomolecules like Deoxyribonucleic Acid (DNA), proteins, and membrane lipids. Lipid peroxidation in Low-Density Lipoprotein (LDL) particles and membranes of hepatocytes are involved in atherosclerosis and liver disease respectively. Non-enzymatic glycosylation of proteins is involved in complications of diabetes. Antioxidant-oxidant system imbalance can result in emergence of free radicals’ destructive effects in long term. We studied the antioxidant effects of a food spice, namely Piper nigrum, on the above-mentioned reactions. Total extracts of the black pepper were obtained and identified. Hepatocytes of rat were exposed to tert-butyl hydroeroxide (TBH) (1.5 m µ) and amount of malondialdehyde (MDA) resulting from lipid peroxidation was measured in presence and absence of the plant extract. Alanine Aspartate Aminotransferase (AST) released from membrane lipid peroxidation was also measured. Glycosylation changes of hemoglobin and LDL oxidation were measured in the presence and absence of the extract and percent of oxidation inhibition was compared with that in control subjects. The results showed that Piper nigrum decreased MDA formation by 17.78% and AST release from hepatocytes by 33.3% at a concentration of 10 µg/ml, and decreased hemoglobin glycosylation by 17.35% and at a concentration of 0.25 µg/ml. The antioxidant effect was very remarkable at the concentration of 1 µg/ml. This study showed that Piper nigrum has a very strong antioxidant effect at applied doses and it can be probably used as an antioxidant and food supplement in diabetic and liver disease patients, and in persons susceptible to atherosclerosis.