Comparison of Antioxidant Effects of the Proton Pump-Inhibiting Drugs Omeprazole, Esomeprazole, Lansoprazole, Pantoprazole, and Rabeprazole

INTRODUCTION: Peptic lesions usually develop when there is an imbalance between aggressive drivers and gastro-protective mediators that guard the lining of the gastrointestinal tract. The most crucial of these mediators are antioxidants, whose loss may predispose to oxidative stress, which is believed to be the main aggravator of several diseases including peptic ulcer. Proton pump inhibitors (PPIs) are drugs that are highly effective and widely used for therapeutic management of peptic disorders through inhibition of gastric acid secretion. In spite of this, oxidative damage may continue to be a major issue that can predispose to future lesions. OBJECTIVE: The present study is designed to explore the possible antioxidant capability of different PPIs, including omeprazole, esomeprazole, lansoprazole, pantoprazole, and rabeprazole, in an aim to suggest an agent that, in addition to its acid-suppression properties, can provide antioxidant profit. METHODS: The antioxidant activity of different PPIs was evaluated calorimetrically to test the ability of each drug to quench oxygen free radical, using the well-known stable free radical α,α-diphenyl-β-picrylhydrazyl (DPPH), and compared to ascorbic acid (AA; vitamin C). The measurements were performed using a spectrophotometer at 517 nm. RESULTS: All the studied drugs reduced DPPH, but to different extents. However, omeprazole and esomeprazole showed the highest ability to scavenge free radicals (50% inhibitory concentrations [IC50s] of the percentage for free radical scavenging activity are 18.7 ± 5.7 and 18.7 ± 5.7, respectively, and the AA equivalents are 83,772 ± 11,887 and 81,732 ± 8,523 mg AA/100 g, respectively). Conversely, lansoprazole, pantoprazole, and rabeprazole might be having no role in this story (IC50s of the percentage for free radical scavenging activity are 49.3 ± 3.1, 49 ± 9.4, and 40.7 ± 7.2, respectively, and the AA equivalents are 30,458 ± 3,884, 32,222 ± 10,377, and 37,876 ± 8,816 mg AA/100 g, respectively). CONCLUSION: Thus, omeprazole and esomeprazole may confer a significant dual action in gastrointestinal protection by providing potent antioxidant properties in addition to their major role as acid-suppression agents. However, further studies are essential to elucidate the mechanism behind the difference between the drugs of the same class.