Atividade antiulcerogênica e anti-inflamatória da casca de croton urucurana (euphorbiaceae) e seus diterpenos clerodanos

Abstract

Croton urucurana is a species known as “sangra d’água”, used in folk treatment of gastric ulcers, common pains, inflammatory processes and even cancers. Previous studies have shown its antiulcerogenic activity, using the methanolic extract of its bark (MECu) in several types of gastric lesions in rats. In the light of promising results, the present study aimed to evaluate the antiulcerogenic and anti-inflammatory activity of the extract from the bark of C. urucurana its retrieved compounds. The protection of the gastric system provide by the MECu and the hydroacetone extract of C. urucurana bark (AECu) was evaluated by the HCl/ethanol induction model in mice, as well as their hexanic (HEX), ethyl acetate (ACT) and hydrometanolic (HMT) fractions of MECu and hexanic (HEXa), ethyl acetate (ACTa) and aqueous (AQUa) fractions of AECu. The content of condensed tannin, hydrolysable and total phenols was quantified, and the tannin rich fraction (ACTa) was less gastroprotective than ACT, which maintained its properties after tannin removal by chromatography with silica gel column (70 to 230 mesh). The phytochemical profile performed by HPLC-DAD-ESI-Q-TOF-MS/MS evidenced the presence of dissaccharides, tannins, flavonoids, alkaloids and diterpenes. Considering the promising activity of ACT and its tannin-free fraction it was subjected to column chromatographic procedures, which allowed the production of four clerodan diterpenes: hardwickiic acid, methyl-12-epi-barbascoate, methyl-3-oxo-12-epi-barbascoate and first report methyl-3-hydroxy-barbascoate. Both ACT and diterpenes were evaluated in vitro in light of the main etiologic factor of gastric ulcer, Helicobacter pylori. All samples were active. In parallel, the anti-inflammatory activity of MECu was evaluated in observation of the paw edema model, leukocyte migration in the peritoneal cavity, as well as antinociceptive by writhing in acetic acid test and formalin test. MECu presented anti-inflammatory and antinociceptive property (involving both the central and peripheral pathways). Based on the results, the diterpenes of greater incidence (hardwickiic acid and methyl-12-epi-barbascoate) were evaluated for both gastroprotective and anti-inflammatory property. In the model of paw edema induced by carrageenan, methyl-12-epi-barbascoate had its peaked of effect in 60 minutes of its administration, inhibiting 58.6% of the edema. The hardwickiic acid had its peaked at 120 minutes of its administration, presenting 57,1% inhibition. Both diterpenes also inhibited the migration of inflammatory cells into the abdominal cavity, with the best rate of inhibition of hardwickiic acid by the dose of 50 mg/kg (61.5%) and methyl-12-epi-barbascoate by a dose of 25 mg/kg (59.9%), whereas indomethacin (15 mg / kg) inhibited 69.5%. In the model of gastric injury induced by HCl/ethanol, hardwickiic acid and methyl 12-epi-barbascoate in the lowest dose had lesion inhibition rates of 82.3% and 90.3%, respectively. Biochemical measurements with gastric tissue showed that these diterpenes decreased inflammatory cell infiltration to the lesion area by reducing myeloperoxidase levels (MPO), and hardwickiic acid was able to reduce lipid peroxidation evidenced by malondialdehyde levels. None of the diterpenes improved levels of reduced glutathione, superoxide dismutase and catalase. These data suggest that diterpenes provide anti-ulcer activity by stimulating cytoprotective factors, inhibiting the migration of inflammatory cells and, the hardwickiic acid capacity, reducing lipid peroxidation. These results reinforce the therapeutic potential of the species, corroborating with its popular use, and indicating that diterpenes contribute significantly to these biological actions.