The structural requirements for the gastric cytoprotective activity of several sesquiterpene lactones are reported. A theoretical-experimental study on the potentially active centers is carried out. The biological evaluation of reduced analogues and the simulation of the molecular interactions between these compounds and an endogenous cysteine residue suggest that the presence of a non sterically hindered Michael acceptor seems to be an essential structural requirement for the cytoprotective activity in this family of compounds. This observation suggests that cytoprotection is mediated through a Michael reaction between the sulfhydryl-containing peptides of the mucosa and Michael acceptors present in the molecules under study. This mechanism of action is in addition to and distinct from the one proposed in our previous paper, namely, that these sesquiterpenes stimulate endogenous synthesis of prostaglandins.

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A pharmacological evaluation of the diuretic activity of Fabiana patagonica Speg. (Solanaceae) was carried out in isotonic saline loaded rats. The data reported in the present work indicate that the acetone extract and infusion of the aerial part of Fabiana patagonica showed a moderate diuretic activity. This activity could be due, in part, to the presence of oleanolic acid isolated as the major metabolite of F. patagonica.

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