Sterol Chemotaxonomy of Marine Pelagophyte Algae

Abstract

Several marine algae of the class Pelagophyceae produce the unusual marine sterol 24-propylidenecholesterol, mainly as the (24E)-isomer. The (24Z)-isomer had previously been considered as a specific biomarker for Aureococcus anophagefferens, the 'brown tide' alga of the Northeast coast of the USA. To test this hypothesis and to generate chemotaxonomic information, the sterol compositions of 42 strains of pelagophyte algae including 17 strains of Aureococcus anophagefferens were determined by GC analysis. A more comprehensive sterol analysis by HPLC and (1)H-NMR was obtained for 17 selected pelagophyte strains. All strains analyzed contained 24-propylidenecholesterol. In all strains belonging to the order Sarcinochrysidales, this sterol was found only as the (E)-isomer, while all strains in the order Pelagomonadales contained the (Z)-isomer, either alone or together with the (E)-isomer. The occurrence of Delta(22) and 24alpha-sterols was limited to the Sarcinochrysidales. The first occurrence of Delta(22)-24-propylcholesterol in an alga, CCMP 1410, was reported. Traces of the rare sterol 26,26-dimethyl-24-methylenecholesterol were detected in Aureococcus anophagefferens, and the (25R)-configuration was proposed, based on biosynthetic considerations. Traces of a novel sterol, 24-propylidenecholesta-5,25-dien-3beta-ol, were detected in several species.

Sterol and genomic analyses validate the sponge biomarker hypothesis

“…The genome of one pelagophyte (Aureococcus anophagefferens) and one demosponge (Amphimedon queenslandica) are publically available and were included in our study. Like other pelagophytes, A. anophagefferens produces trace amounts of 24-ipc (<0.05%) during 24-propylidenecholesterol synthesis (16). In contrast, a recent study on A. queenslandica identified cholesterol (C 27 ), brassicasterol (C 28 ), and an unidentified sterol as its major components (17).…”

The molecular record of Cryogenian sponges – a response to Antcliffe (2013)

“…), but analytically resolvable, sterane isomer 24‐ n ‐propylcholestane (24‐npc), which originates principally from the sterols of marine pelagophyte algae (Giner et al . ). 24‐npc is typically the dominant C 30 sterane detected in marine Phanerozoic oils and rocks from all lithologies (Moldowan ; Moldowan et al .…”

Empirical links between trace metal cycling and marine microbial ecology during a large perturbation to Earth's carbon cycle

“…C 28 steroids (preserved as 24-methylcholestanes) are important in higher order endosymbiotic red algal lineages that were not dominant or diverse until late Mesozoic time and younger (Grantham and Wakefield, 1988), including haptophytes and diatoms, but also in some prasinophytes from the green lineage (Kodner et al, 2008;Volkman, 2003). The C 30 steranes, 24-n-propylcholestanes are mainly derived from sterol precursors produced by the exclusively marine algal class Pelagophyceae, although these have also been reported as minor constituents of foraminifera (Giner et al, 2009;Grabenstatter et al, 2013).…”