Bio-active cardenolides from the leaves of Nerium oleander.

A bioactivity directed isolation of the methanolic extract of the fresh, uncrushed leaves of Nerium oleander showing a central nervous system (CNS) depressant effect in mice has been undertaken. As a result, four CNS depressant 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 including one-dimensional and two-dimensional NMR (COSY-45, NOESY, J-resolved, HMQC and HMBC). The known compounds have been indentified through spectral studies and comparison of data with those reported in the literature.