Thioic O-acid ester in sulfolipid isolated from freshwater picoplankton cyanobacterium, Synechococcus sp

A thioic O-acid ester-containing sulfolipid (thionsulfolipid) was isolated from cells of picoplankton cyanobacterium, Synechococcus sp. The lipid accounted for about 0.2% of the lyophilized cells. The lipid was subjected to mild alkaline hydrolysis, and the structures of the hydrolysis products were identified by infrared spectra, mass and nuclear magnetic resonance spectrometries, as fatty acids and hexadecane-, hexadecene- and tetradecanethioic S-acids. Thioic S-acid was further confirmed by the synthesis of hexadecanethioic S-acid from palmitoylchloride and hydrogen sulfide. The positional distribution of the thioic acid ester in the lipid was determined by beta-galactosidase, sulphur-oxygen exchange reaction using silver nitrate, and lipase hydrolysis of the diacylglycerol derived from the lipid. The structure of the thionsulfolipid was identified as 6-sulfo-alpha-D-quinovopyranosyl(1-->1')-2'-O-acyl-3'-O-thioacy l -2-glycerol. When cells of HL 60, as a human lymphoma, were cultured with thionsulfolipid, 61% of the cell growth was inhibited at the concentration of 200 micrograms/ml. The lipid was toxic against minnows (Tanichtys albonubes). The LD50 was 20 ppm. Thioic O-acid ester-containing lipid (thionsulfolipid) has not been found in any other photosynthetic organisms.