2′-Methyl and 1′-xylosyl derivatives of 2′-hydroxyflexixanthin are major carotenoids of Hymenobacter species

Bacteria related to the genus Hymenobacter are colored intensely red due to their carotenoid pigmentation. Using high-resolution mass spectrometry and comparison to the literature reports, we previously isolated and presumptively identified seven structurally related carotenoids from representative Hymenobacter-like strains. After further analysis using one- and two-dimensional ¹H NMR, UV-vis, and circular dichroism spectroscopies, we determined that the major carotenoid present in these strains is 2′-hydroxyflexixanthin, as proposed previously by others in a related organism. Furthermore, we have identified three novel, related carotenoids abundant in these strains as 1′-xylosyl-2′-hydroxyflexixanthin, 2′-methoxyflexixanthin, and 3-deoxy-2′-methoxyflexixanthin.