Sterols of four dinoflagellates from the genus Prorocentrum

The compositions of 5-desmethyl sterols and 4-methyl sterols in four specie s of marine dinoflagellates of the genus Prorocentrum (viz., P. micans Ehre nberg, P. minimum (Pavillard) Schiller, P. balticum (Lev.) Lemm and P. mexi canum Tafall) were identified by capillary gas chromatography-mass spectrom etry as part of a study to identify signature lipids for dinoflagellates in marine organic matter. Complex mixtures were found in each species with ov er 20 sterols identified in all. All species contained the same core group of sterols, but there were significant differences in the proportions of th e various sterols. Two distinct groupings could be discerned in the sterol patterns. The ii-methyl sterol 4 alpha,23,24-trimethyl-5 alpha-cholest-22E- en-3 beta-ol (dinosterol), which is common in many dinoflagellates, predomi nated in P, balticum and in P, minimum whereas in the closely related speci es P, micans and P. mexicanum the major sterol was cholesterol. A novel mon ounsaturated C-23 sterol having a much shortened side-chain was found in P, balticum and P. minimum and both P. balticum and P. minimum contained peri dinosterol (4 alpha,23,24-trimethyl-5 alpha-cholest-17(20)-en-3 beta-ol). 2 4-Methylenecholesterol was only found in P. minimum, where it comprised ove r one-third of the sterols. The steroid ketone dinosterone occurred in P. b alticum, but none of the other species contained steroid ketones. Although all the sterol distributions were broadly similar, the presence or absence of specific components might be a useful chemotaxonomic tool for distinguis hing between closely related species. (C) 1999 Elsevier Science Ltd. All ri ghts reserved.