Antihypertensive, antiatherosclerotic and antioxidant activity of triterpenoids isolated from Olea europaea, subspecies africana leaves

For the first time a biossay-directed study of triterpenoids isolated from the leaves of Olea europaea from Greece, from wild African olive and from a cultivar of O. europaea grown in Cape Town was reported. The experiment was undertaken since our preliminary analyses showed that the African wild olive leave is rich in triterpenoids and contain only traces of the glycoside oleuropein, which is typical for the European olive leaves. The isolate of the African wild olive leaves (AO) used in the experiments was found to contain 0.27% 1:1 mixture of oleanolic acid and ursolic acid, named olcuafricein. The isolate of Greek olive leaves (GO) was found to contain 0.71% oleanolic acid, and the Cape Town cultivar (CT) contained 2.47% oleanolic acid. No ursolic acid was found in either GO or CT. The antihypertensive, diuretic, antiatherosclerotic, antioxidant and hypoglycemic effects of authentic oleanolic and ursolic acid and the three isolates (GO, AO and CT) were studied on Dahl salt-sensitive (DSS), insulin-resistant rat genetic model of hypertension. All three isolates, in a dose 60 mg/kg b.w. for 6 weeks treatment, prevented the development of severe hypertension and atherosclerosis and improved the insulin resistance of the experimental animals. GO, OA and CT isolates could provide an effective and cheap treatment of this particular, most common type of salt-sensitive hypertension in the African population. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.