Abstract: The chemical constituents of Onchidium struma collected from Chongming Island in Shanghai of China were analyzed. The compounds were isolated and purified by various chromatographic techniques and recrystallization.Their structures were determined on the basis of physicochemical properties and spectral data.Five compounds were isolated and identified as 2,2′-oxybis(1,4-di-tert-butylbenzene) (1),cholesterol (2),batilol (3),ethyloctadecanoate (4) and stearic acid (5).Compound 1 was isolated from natural resources for the first time.Moreover,all these compounds were isolated from genus Onchidium for the first time.

Key words: Onchidium struma, extraction and isolation, chemical constituent, structural elucidation