Dihydroxylycopene diglucoside diesters: a novel class of carotenoids from the phototrophic purple sulfur bacteria Halorhodospira abdelmalekii and Halorhodospira halochloris.

Abstract

The carotenoids in Halorhodospira abdelmalekii and Halorhodospira halochloris were analyzed by spectroscopic methods. The carotenoid composition of the two species was almost the same. Both species contained substantial amounts of unusual carotenoid glycoside fatty acid esters, which have been found for the first time in phototrophic purple bacteria. Methoxy-hydroxylycopene glucoside was a major component, and dihydroxylycopene diglucoside and dihydroxylycopene diglucoside diester were also found. Lycopene, rhodopin, and 3,4,3',4'-tetrahydrospirilloxanthin were present in very small amounts. Methoxy, glucosyl, and glucosyl ester groups were observed as substituents at the positions of the two original hydroxyl groups of dihydroxylycopene and made up approximately 20, 50, and 20%, respectively, of the total end groups (100%). The fatty acid components of the three carotenoid glucoside esters were the same (C12:0 and C14:1) and were rare in the cellular lipids of the two species.