The therapeutic lead potential of metabolites obtained from natural sources for the treatment of peptic ulcer Luiz Carlos Klein-Ju ´ nior • Jose ´ Roberto Santin • Rivaldo Niero • Se ´rgio Faloni de Andrade • Valdir Cechinel-Filho Received: 27 July 2012 / Accepted: 4 November 2012 / Published online: 22 November 2012 Ó Springer Science+Business Media Dordrecht 2012 Abstract For over a century, ulcer has been a major cause of morbidity and mortality. Its treatment has progressed from vagotomy to proton pump inhibitors. However, the drugs used produce many adverse effects and are less effective than they ought to be. Therefore, there is a growing interest in alternative therapies and the use of natural products. This review emphasizes recent studies involving naturally occur- ring antiulcer metabolites, categorized according to their chemical structure. Both terrestrial and marine sources are included. More than a hundred and fifty different compounds are presented, and where possi- ble, their main mechanisms of action are summarized. Considering that Helicobacter pylori is an important causal factor in the pathogenesis of ulcer disease, an overview of some natural compounds with anti-H. pylori activity is presented. Keywords Ulcer Á Secondary metabolites Á Gastroprotection Introduction The main function of gastrointestinal tract is digestion and absorption of nutrients in order to maintain the functioning of the organism. For this purpose, this system must have the right conformation, with a large surface area that permits high absorption, and glands that produce digestive juices. One of the segments of the gastrointestinal tract is the stomach. This organ is comprised of several layers of smooth muscle, lined by a mucous membrane. It is anatomically divided into four regions: the cardia, the fundus, the body and the antrum (Merchant 2007; Schubert and Peura 2008). Like the other organs of the body, the stomach can be stricken by pathologies. One of the most frequent illnesses affecting the stomach is peptic ulcer, defined as chronic lesions, usually solitary, that penetrate the muscularis mucosae layer, forming a cavity. Peptic ulcers can occur in any part of the gastrointestinal tract that is exposed to the aggressive action of gastric acid. The appearance of this type of lesion is more common in the stomach or duodenum. While gastric ulcers are located in the stomach, often along the lesser curvature in the transition zone from the corpus to the antrum mucosae, duodenal ulcers are located in the duodenal bulb (Najm 2011). The main clinical manifestations of peptic ulcer include a history of nighttime awakening and localized epigastric pain, which are relieved by food intake, antacids or antisecretory agents. Other typical symp- toms, present in 80–90 % of patients, include an L. C. Klein-Ju ´nior (&) Á J. R. Santin Á R. Niero Á S. F. de Andrade Á V. Cechinel-Filho Programa de Po ´s-Graduac ¸a ˜o em Cie ˆncias Farmace ˆuticas, Nu ´cleo de Investigac ¸o ˜es Quı ´mico-Farmace ˆuticas, Universidade do Vale do Itajaı ´, UNIVALI, Rua Uruguai, 458, Itajaı ´, Santa Catarina 88302-202, Brazil e-mail: lcarlosk@gmail.com 123 Phytochem Rev (2012) 11:567–616 DOI 10.1007/s11101-012-9262-4