Characterization of light-harvesting pigments of Chloroflexus aurantiacus. Two new chlorophylls: oleyl (octadec-9-enyl) and cetyl (hexadecanyl) bacteriochlorophyllides-c

Abstract

The bacteriochlorophyll-c pigment contained in the chlorosomes of the phototrophic and thermophilic bacterium Chloroflexus aurantiacus is shown to comprise, in the least, 10 constituents, viz. the 2a-epimeric pairs [i.e., the (2aR,7S,8S)- and (2aS,7S,8S)-diastereoisomers in 2:1 ratio] of five bacteriochlorophyllide-c esters. All compounds were fully characterized by 1H and 13C NMR spectroscopy, and by mass spectra. They include the bacteriochlorophyllides-c of geranylgeranio, phytol, and stearol(octadecan-1-ol), which have been reported previously but have not yet been completely characterized, and two novel bacteriochlorophylls-c, viz. the bacteriochlorophyllides-c of the non-isoprenoid alcohols ‘cetol’(hexadecan-1-ol) and ‘oleol’(octadec-9-en-1-ol).