Major Carotenoids of Meiothermus ruber Are Deinoxanthin Glucoside Esters, Not Meiothermoxanthin Glucoside Esters

Abstract

Meiothermus ruber DSMZ 1279T was isolated from a hot spring in Kamchatka and was red in color. The major carotenoid present was reported to be 1'-(β-d-glucopyranosyloxy)-3,4,3',4'-tetradehydro-1',2'-dihydro-β,ψ-caroten-2-one after saponification (Burgess et al. J. Nat. Prod. 1999, 62, 859-863). In this study, we purified the major carotenoids in this species without saponification. We then reidentified the major carotenoids present using spectroscopic data, including electronic circular dichroism (ECD), 1H NMR, rotating-frame nuclear Overhauser effect spectroscopy (ROESY), 13C NMR, heteronuclear single-quantum correlation spectroscopy (HSQC), heteronuclear multiple-bond correlation spectroscopy (HMBC), and MS, and enzymatic hydrolysis of fatty acid moieties and found deinoxanthin glucoside iso fatty acid esters. The bound fatty acids present included four iso types, and their composition differed from cellular lipids. Moreover, the previously identified carotenoid glucoside was a saponification artifact of deinoxanthin glucoside esters. Ketomyxocoxanthin glucoside esters and 1'-hydroxytorulene glucoside esters were also present. On the basis of the identification of carotenoids and the whole genome sequence of M.ruber, we propose a carotenoid biosynthetic pathway and note the corresponding genes.