Abstract: The isolation and purification of the compounds were performed by silica gel,Sephadex LH-20,ODS and HPLC methods,and their structures were determined by comparing their physicochemical characters and spectral data with literatures.Seven compounds were isolated from the extracts of Halichondria sp.and inden tified as 4α-Isocyanogorgon-11-Ene(1),Homoverrucosanol(2),neoverrucosanol(3),5α,6α-Epoxy-(22E)-ergosta-8,14,22-triene-3β,7α-diol(4),5α,8α-epidioxy-(22E, 24R)-ergosta-6,22-dien-3β-ol(5), (22E, 24R)-ergosta-7,22-diene-3β,5α, 6α,9α-tetrol(6),3β,5α,9α,14β-tetrahydroxy-(22E)-ergosta-7,22-dien-6-one(7).All the compounds were isolated from Halichondria sp. for the first time,and compound 1 and 3 exhibited weak cytotoxicity against the HeLa cell line.The IC₅₀ of them is 33.7 μM and 43.8 μM respectively.

Key words: Halichondria sp, chemical composition, spectroscopic analysis, bioactivity