Carotenoid pigments from Rhodococcus rhodochrous RNMS1: Two monocyclic carotenoids, a carotenoid monoglycoside and carotenoid glycoside monoesters.

Abstract

Four kinds of carotenoid pigments were found in Rhodococcus rhodochrous RNMS1. Spectroscopic and chemical evidence showed two of them to be monocyclic carotenoids each containing a tertiary hydroxyl group at C1′, and their structures were determined as 1′,2′-dihydro-β,ψ-caroten-1′-ol and 1′-hydroxy-1′,2′-dihydro-β,ψ-caroten-4-one. The other two were novel carotenoid derivatives, one being a monoglycoside of the latter carotenoid and the other monoesters of this carotenoid glycoside, which were esterified with nine major fatty acids at the C6 hydroxyl group of the glucose moiety. The fatty acids consisted of four saturated (C16:0–C19:0), four mono-unsaturated (C18:1– C21:l) and one branched-chain (10-methyl C19:0) acid, including the odd-numbered ones. The structures were determined to be 1′-[(β-d-glucopyranosyl)oxy]-1′,2′-dihydro-β,ψ-caroten-4-one and 1′-[(6-O-acyl-β-d-glucopyranosyl)oxy]-1′,2′-dihydro-β,ψcaroten-4-one.