A new carotenoid, 6′-hydroxy-3′-didehydrolutein, produced by recombinant Escherichia coli that expresses the violaxanthin biosynthesis and chaperone AtCYO1 genes — Its structure and antioxidant activities

Abstract

Recombinant Escherichia coli cells, which express the higher-plant CaZEP (zeaxanthin epoxidase) and AtCYO1 (molecular chaperone) genes and an NADPH regeneration system in addition to the IDI, crtE, crtB, crtI, crtY, and crtZ genes for zeaxanthin biosynthesis, were cultured in 2 × YT medium for the efficient production of antheraxanthin and violaxanthin. The carotenoids accumulated in the cells were purified by two-phase partition, silica gel column chromatography, and preparative silica gel HPLC. Mass spectrometry and nuclear magnetic resonance analyses of these carotenoids revealed that a novel carotenoid, determined to be (3R,6′S)-3,6′-dihydroxy-β,ε-caroten-3′-one and named as 6′-hydroxy-3′-didehydrolutein, was produced in addition to zeaxanthin, antheraxanthin and violaxanthin. It is likely that the new carotenoid was generated from an unstable epoxy-carotenoid antheraxanthin that was synthesized from zeaxanthin with CaZEP. Its antioxidant activities were also examined.