Associate Professor Hokkaido University 函館市港町3-1-1, Japan
Abstract: Carotenoids are fat-soluble pigments with yellow- to red-color. They are produced by plants and some microorganisms, but not animals and show various biological activity. To identify novel carotenoids with unique structure and biological activity, we analyzed pigments produced by marine bacteria. Here, we successfully isolated several novel monocyclic carotenoids including 2'-isopentenylsaproxanthin (2' -(3-methylbut-2-enyl)-3', 4'-didehydro-1', 2'-dihydro-β, ψ-carotene-3, 1'-diol), 3’’-hydroxy-2’-isopentenylsaproxanthin and 2-hydroxylflexixanthin through chromatography and nuclear magnetic resonance analysis. Furthermore, in culturing under alkaline and oxidative stress conditions, 2'-isopentenylsaproxanthin production was increased up to 3-fold via upregulating gene expression of carotenoid biosynthetic enzymes including isopentenyl-diphosphate isomerase. In addition, monocyclic-type carotenoid 2'-isopentenylsaproxanthin exhibited higher radical scavenging and singlet oxygen quenching activities compared to dicyclic-type β-carotene. 2-Hydroxylflexixanthin downregulated mRNA expression of proinflammatory cytokines, which induce insulin resistance and metabolic syndrome, against activated macrophages. Marine bacteria have the potential as useful bioresources for obtaining functional monocyclic carotenoids.
