Anti-inflammatory activity of two cucurbitacins isolated from Cayaponia tayuya roots

Fractionation of an anti-inflammatory extract from Cayaponia tayuya roots yielded two active compounds, identified as 23,24-dihydrocucurbitacin B (1) and cucurbitacin R (2). Both were evaluated for their anti-inflammatory activity on several experimental models of pain and inflammation. In addition, their cytotoxicity and effects on leukotriene B-4 (LTB4) formation were evaluated in rat polymorphonuclear leukocytes. Both compounds showed activity in the following models: carrageenan-induced mouse paw oedema (1, 4 mg/kg p. o., 46% inhibition at 3 h), phospholipase A(2)-induced mouse paw oedema (2, 3 mg/kg i.p., 61% inhibition at 60 min), serotonin-induced mouse paw oedema (1 and 2, 0.5 mg/kg s.c., 73% and 79% inhibition, respectively), 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced acute ear oedema (2, 36% inhibition at 4 mg/kg p.o., and 87% inhibition at 0.1 mg/ear topically). The Compounds Were also active against the inflammation induced by repeated application of TPA on Mouse ears, affecting both the oedema itself (1 and 2 at 0.1 mg/ ear, 44% and 56% inhibition, respectively) as well as cell infiltration (68% and 69%, respectively). The activity of both compounds against oedema induced by serotonin was not modified by the glucocorticoid receptor antagonist mifepristone; however, the protein synthesis inhibitor cycloheximide abolished the anti-inflammatory response in both cases. Neither compound modified the production of LTB4 in rat polymorphonuclear leukocytes, nor did they exhibit analgesic properties at the dose assayed.