Dendrocyin: An Isocucurbitacin with Novel Cyclic Side Chain from Dendrosicyos socotrana.

Abstract Dendrosicyos socotrana Balf.f. is a unique species (Cucurbitaceae) native to Socotra island in the horn of Africa. From the chloroform extract of the stems, A new isocucurbitacin (Dendrocyin) with unusual cyclization in the side chain; 24β-ethoxy-20-25-epoxy-3α,16α-dihydroxy-9-methyl-19-norlanost-5(6) ene-2,11,22-trione has been isolated alongside isocucurbitacin R. Their structural configuration were established by usual spectroscopic ( 1 H NMR, 13 C NMR and DEPT) and two-dimensional NMR techniques ( 1 H– 1 H Cosy, HMBC and HMQC).