In vitro synthesis of betaxanthins using recombinant DOPA 4,5-dioxygenase and evaluation of their radical-scavenging activities.
Betalamic acid, the chromophore of betaxanthins, was enzymatically synthesized on a large scale from l-dihydroxyphenylalanine (L-DOPA) using recombinant Mirabilis jalapa DOPA 4,5-dioxygenase. After synthesis, proline was directly added to the concentrated reaction mixture to generate proline-betaxanthin. The molecular mass and nuclear magnetic resonance spectrum of the purified product were identical to those previously reported for proline-betaxanthin. Twenty-four betaxanthin species were synthesized by the condensation reaction of purified betalamic acid and amino acids or amines. An HPLC protocol was established for identifying the different betaxanthin species. Proline-, dopamine-, and γ-aminobutyric acid (GABA)-betaxanthins were prepared as representative betaxanthins under large-scale conditions, and their 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activities were compared against those of known antioxidants. GABA-betaxanthin showed comparatively low activity, whereas dopamine-betaxanthin had similar activity to the red pigment betanin and the anthocyanin cyanidin 3-glucoside. Proline-betaxanthin had the highest activity of the three synthesized compounds and was similar to the flavonoid quercetin.
Department of Biotechnology and Life Science, Faculty of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
Hiroshi
H
Sekiguchi
Yoshihiro
Y
Ozeki
Nobuhiro
N
Sasaki
D050860:Betaxanthins / Q000138:chemical synthesis* / Q000737:chemistry; D004295:Dihydroxyphenylalanine / Q000737:chemistry; D049308:Dioxygenases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016166:Free Radical Scavengers / Q000737:chemistry*; D039282:Mirabilis / Q000201:enzymology*; D015394:Molecular Structure; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D050860:Betaxanthins; D016166:Free Radical Scavengers; D010940:Plant Proteins; D011994:Recombinant Proteins; D004295:Dihydroxyphenylalanine; D049308:Dioxygenases