Novel 3‐Oxo‐ and 3,24‐Dinor‐2,4‐secooleanane‐Type Triterpenes from Terminalia ivorensis A. Chev.

Two new oleanane‐type triterpenes named ivorengenin A (=3‐oxo‐2α,19α,24‐trihydroxyolean‐12‐en‐28‐oic acid; 1 ) and ivorengenin B (=4‐oxo‐19α‐hydroxy‐3,24‐dinor‐2,4‐secoolean‐12‐ene‐2,28‐dioic acid; 2 ), together with five known compounds, arjungenin, arjunic acid, betulinic acid, sericic acid, and oleanolic acid, were isolated from the barks of Terminalia ivorensis A. Chev . (Combretaceae). Their structures were established on the basis of 1D‐ and 2D‐NMR data, and mass spectrometry. A biogenetic pathway to the formation of these compounds from sericic acid, isolated as the major compound from this plant, was proposed. The antioxidant activities of different compounds were investigated by means of the 2,2‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) assays, and IC₅₀ values were calculated and compared with Trolox activity. Antiproliferative activities of the isolated compounds were also evaluated against MDA‐MB‐231, PC3, HCT116, and T98G human cancer cell lines, against which the compounds showed significant cytotoxic activities.