LC-MS/APCI identification of glucoside esters and diesters of astaxanthin from the snow alga Chlamydomonas nivalis including their optical stereoisomers

► The composition of astaxanthin optical isomers in Chlamydomonas nivalis from different localities differs. ► A high content of the 3R,3′R isomer is reported for the first time in a phototrophic organism. ► The proportion of astaxanthin esters and glycosides is highly variable. ► Despite the differences in the fatty acid composition, the unsaturation index is identical.