The chemical constituents of marine soft coral Sinularia tenella Li. collected from Hainan Sanya are reported herein for the first time. Five cembrenolides, i. e., dihydroflexibilide, flxibilide, sinulariolide, (1R, 4R, 5R, 8S, 9S, 12S, 13)-9-acetoxy- 5,8:12,13- diepoxy-cembr-15(17)-en-16,4-olide and (1R, 4R, 5S, 12S, 13S)-5- acetoxy-12,13-epoxy-cembr-8E,15(17)-dien-16,3-olide were isolated and identified by means of spectroscopic method. Base on the 1^H-1^H COSY, HMQC and HBMC experiments, all the 1^H NMR and the 13^C NMR signals of dihydroflexibilide were assigned for the first time in this paper.

Key words: 2D NMR SPECTROMETRY, CHEMICAL COMPOSITION, CYTOTOXICITY TEST, LACTONE DERIVATIVE, DITERPENE ALKALOID, SOFT CORAL