Oleanonic acid, a 3-oxotriterpene from Pistacia, inhibits leukotriene synthesis and has anti-inflammatory activity

One of the best known bioactive triterpenoids is oleanolic acid, a widespre ad 3-hydroxy-17-carboxy oleanane-type compound. In order to determine wheth er further oxidation of carbon 3 affects anti-inflammatory activity in mice , different tests were carried out on oleanolic acid and its 3-oxo-analogue oleanonic acid, which was obtained from Pistacia terebinthus galls. The la st one showed activity on the ear oedema induced by 12-deoxyphorbol-13-phen ylacetate (DPP), the dermatitis induced by multiple applications of 12-O-te tradecanoyl-13-acetate (TPA) and the paw oedemas induced by bradykinin and phospholipase A(2). The production of leukotriene B-4 from rat peritoneal l eukocytes was reduced by oleanonic acid with an IC50 of 17 muM. Negligible differences were observed in the response of both triterpenes to DPP, brady kinin. and phospholipase A(2), while oleanonic acid was more active on the dermatitis by TPA and on the in vitro leukotriene formation. In conclusion, the presence of a ketone at C-3 implies an increase in the inhibitory effe cts on models related to 5-lipoxygenase activity and on associated in vivo inflammatory processes. (C) 2001 Elsevier Science B.V. All rights reserved.