Bio-active cardenolides from the leaves of Nerium oleander

A bioactivity directed isolation of the methanolic extract of the fresh, un crushed leaves of Nerium oleander showing a central nervous system (CNS) de pressant effect in mice has been undertaken. As a result, four CNS depressa nt cardenolides including a new cardenolide, neridiginoside and three known constituents, nerizoside,neritaloside and odoroside-H, have been isolated which exhibited CNS depressant activity in mice at a dose of 25 mg/kg. The structure of neridiginoside was elucidated as 3 beta-O-(D-diginosyl)-5 beta ,14 beta-dihydroxy-card-20(22)-enolide, using spectroscopic methods includi ng one-dimensional and two-dimensional NMR (COSY-45, NOESY, J-resolved, HMQ C and HMBC). The known compounds have been indentified through spectral stu dies and comparison of data with those reported in the literature. (C) 1998 Elsevier Science Ltd. All rights reserved.