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Part-1Review on Antiulcer LiteratureOCOOHHOHOPGE 2 13HCOOHHOHOOHPGI 2 14COOHOHHOMisoprostol 15Figure 7: Structures of the other classes of drugs used in treatment of peptic ulcers.1.2.6. Proton Pump Inhibitors (PPIs)Proton pump is the ultimate mediator of gastric acid secretion by parietal cells. With theidentification of H + /K + -ATPase as the primary gastric proton pump, it was proposed thatactivation of H + secretion occurred by incorporation of H + /K + -ATPase rich tubulovesiclesinto the apical plasma membrane and that the pumps were re-sequestered back into thecytoplasmic compartment on return to the resting state. 41 Inhibition of the protonspumping H + /K + -ATPase as a means of controlling gastric pH has attracted considerableattention in recent years with the discovery of benzimidazole sulfoxide class of antisecretoryagents. In 1973, Ruwart et al., 42 identified timoprazole 16 as one of the firstwell-defined inhibitor of gastric proton pump. Timoprazole was followed by more potentpicoprazole 17 (1976) and omeprazole 43 18 (1979). Chemically, the basic structureconsists of substituted benzimidazole ring & a substituted pyridine ring connected to eachother by a methylsulfinyl chain. Clinically used PPIs include Omeprazole 18,Lansoprazole 19, Rabeprzole 20, Pantoprazole 21 and Esomeprazole 22.13