Notandolide, a new cembranolide isolated from the soft coral Sinularia notanda, and the role of lactone in the cytotoxic activity of cemabranoids

A chemical investigation of the CH[2]CI[2] extract of the Formosan soft coral, Sinularia notanda Tixier-Durivault, has led to the isolation of a new cembrane-based diterpenoid with alpha-methylene-epsilon-lactone notandolide. The chemical structure of the new metabolite, including its relative stereochemistry, has been determined on the basis of extensive spectral analyses including 2D NMR experiments [[1]H-[1]H COSY, HMQC, HMBC, and NOESY] and by NMR spectral comparison. A simple comparative study between the cytotoxic activity of a cembranolide and that of its hydrolyzed products further proved that the intact lactone ring in marine cembranolides might be essential for inhibition of growth of cancer cells