Peptic ulcers are a common disorder of the entire gastrointestinal tract that occurs mainly in the stomach and the proximal duodenum. This disease is multifactorial and its treatment faces great difficulties due to the limited effectiveness and severe side effects of the currently available drugs. The use of natural products for the prevention and treatment of different pathologies is continuously expanding throughout the world. This is particularly true with regards to flavonoids, which represent a highly diverse class of secondary metabolites with potentially beneficial human health effects that is widely distributed in the plant kingdom and currently consumed in large amounts in the diet. They display several pharmacological properties in the gastroprotective area, acting as anti-secretory, cytoprotective and antioxidant agents. Besides their action as gastroprotectives, flavonoids also act in healing of gastric ulcers and additionally these polyphenolic compounds can be new alternatives for suppression or modulation of peptic ulcers associated with H. pylori. In this review, we have summarized the literature on ninety-five flavonoids with varying degrees of antiulcerogenic activity, confirming that flavonoids have a therapeutic potential for the more effective treatment of peptic ulcers.

Essential oil from Citrus aurantium and the monoterpene limonene are widely used flavoring agents that are found in some common food items. This specie is also used medicinally throughout the world to treat gastritis and gastric disorders. Therefore, biological assays were performed in vivo on essential oil of C. aurantium (OEC) and its majority compound limonene (LIM) to evaluate their effect on gastric mucosa. The OEC (250 mg/kg, p.o.) and LIM (245 mg/kg, p.o.) provided effective (99%) gastroprotection against lesions induced by absolute ethanol and NSAID (non-steroidal anti-inflammatory drug) in rats. OEC and LIM do not interfere with gastric H(+) secretion, serum gastrin or glutathione (GSH) level in gastric mucosa. But the gastroprotective action of OEC and LIM occurs due to an increase in the gastric mucus production induced by conserving the basal PGE(2) levels after challenge by agents harmful to the gastric mucosa. Given that LIM and OEC are excellent flavoring agents and also present gastroprotective actions, they can be regarded as a promising target for the development of a new drug for the prevention of gastric damage.

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Citrus lemon (CL) belongs to Rutaceae family and is popularly known in Brazil as limão siciliano. The phytochemical analysis of CL fruit bark essential oil showed two majority components, limonene (LIM) and β-pinene (PIN). This study aimed to evaluate the gastroprotective mechanism of action from CL, LIM and PIN in ethanol- and indomethacin-induced gastric ulcers and its in vitro anti-Helicobacter pylori activity. After ethanol-induced gastric ulcer, the ulcer area was measured and the stomachs were destined to histology (HE and PAS), immunohistochemistry for HSP-70 and VIP and glutathione (GSH) measurement. The involvement of nitric oxide (NO) and sulfhydryl (SH) compounds was determined. The ulcer area for indomethacin-induced gastric ulcers was measured. PGE₂ concentration was biochemically measured. The minimum inhibitory concentration (MIC) against H. pylori was determined in vitro. In ethanol model, CL and LIM demonstrated 100% of gastroprotection, while PIN did not exert effective gastroprotection (53.26%). In the indomethacin model, CL and LIM offered effective gastroprotection but PIN did not show gastroprotective effect. The gastric ulcer area of rats pretreated with NO-synthase inhibitor or SH-blocker was decreased in comparison to the control group. The MIC obtained for CL was 125 μg/mL, for LIM was 75 μg/mL and for PIN was 500 μg/mL. The gastroprotective effect of CL and LIM was involved with increasing in mucus secretion, HSP-70 and VIP, but not with GSH, NO or SH compounds. CL gastroprotective mechanism is involved with PGE₂. PIN did not present gastroprotective activity.

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