Identification of the free and conjugated sterol in a non‐photosynthetic diatom,Nitzschia alba, as 24‐methylene cholesterol

Publisher Website
Google Scholar
Abstract
Previous studies on the sterol fraction of the nonphotosynthetic marine diatom,Nitszchia alba, indicated the major sterol to be either brassicasterol (24R‐methylcholesta‐5,22‐dien‐3β‐ol) or 22‐dehydrocampesterol (24S‐methylcholesta‐5,22‐dien‐3β‐ol) on the basis only of gas chromatographymass spectral analysis. The present studies using nuclear magnetic resonance, infrared, and gas chromatography‐mass spectrometry on the free and bound sterol fractions isolated by preparative thin layer chromatography showed the presence in both fractions of a single sterol, with spectral and chromatographic properties identical with those reported for 24‐methylenecholesterol (ergosta‐5,24(28)‐dien‐3β‐ol). This sterol may be the precursor of 24‐methyl sterols found in diatoms. The bound sterol fraction was found to consist of a single compound identified as 24‐methylenecholesterol sulfate. No sterol esters or sterol glycosides were detected.