Sterols and fatty acids of the marine diatom biddulphia sinensis

Abstract Nine sterols, most showing Δ 5 - or Δ 5,22 -unsaturation, were identified in the marine diatom Biddulphia sinensis . One sterol, cholesta-5,22 E -dien-3β-ol, comprised 70–80% of the total sterols which is the first such predominance noted in a diatom. The only Δ 7 -sterol detected was cholest-7-en-3β-ol and this was a very minor component. A sterol showing unusual side-chain alkylation,23,24-dimethylcholesta-5,22 E -dien-3β-ol, was identified for the first time in a diatom. Total fatty acids exhibited a predominance of Δ 9 - 16:1, 14:0, 20:5 and 16:0, typical of diatoms, although the proportions of these acids were found to vary with culture maturity. n -Heneicosahexaene was the major hydrocarbon together with a small amount of squalene.