Identification of a “pool” of lipid photoproducts in senescent phytoplanktonic cells

The photodegradation of different lipid compounds was studied in killed cells of Phaeodactylum tricornutum and Dunaliella sp. Chlorophyll phytyl chain was photodegraded to 6,10,14-trimethylpentadecan-2-one and 3-methylidene-7,11,15-trimethylhexadecan-1,2-diol, sterols to 5α- and 6α/6β-hydroxysterols, carotenoids to loliolide and iso-loliolide, and unsaturated fatty acids to C7–C11 ω-oxocarboxylic and α,ω-dicarboxylic acids. After elimination of the insufficiently specific photoproducts, 3-methylidene-7,11,15-trimethylhexadecan-1,2-diol, 5α- and 6α/6β-hydroxysterols, C7–C11 ω-oxocarboxylic and α,ω-dicarboxylic acids (with C9 as the most abundant species) were selected to constitute a “pool” of useful indicators of photooxidative alterations of phytoplankton.