Taraxasterane- and ursane-type triterpenes from Nerium oleander and their biological activities

Two new taraxasterane-type triterpenes, 20β,28-epoxy-28α-methoxytaraxasteran-3β-ol (1) and 20β,28-epoxytaraxaster-21-en-3β-ol (2), were isolated from an ethyl acetate extract of the leaves of Nerium oleander, together with ursane-type triterpenes, 28-nor-urs-12-ene-3β,17β-diol (3) and 3β-hydroxyurs-12-en-28-aldehyde (4). The structures of 1 and 2 were established on the basis of their spectroscopic data. Anti-inflammatory activity of 1−4 was examined on the basis of inhibitory activity against the induction of intercellular adhesion molecule-1 (ICAM-1). Cytotoxic activity of 1−4 was evaluated against four human cell lines, A-549, WI-38, VA-13, and HepG2 cells.