Sekiguchi Hiroshi, Ozeki Yoshihiro, Sasaki Nobuhiro
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.
J Agric Food Chem. 2010 Dec 8;58(23):12504-9. doi: 10.1021/jf1030086. Epub 2010 Nov 8.
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.
甜菜氨酸，即甜菜红素的发色团，使用重组紫茉莉多巴4,5 -双加氧酶从L -二羟基苯丙氨酸（L - DOPA）大规模酶促合成。合成后，将脯氨酸直接添加到浓缩反应混合物中以生成脯氨酸 - 甜菜红素。纯化产物的分子量和核磁共振光谱与先前报道的脯氨酸 - 甜菜红素相同。通过纯化的甜菜氨酸与氨基酸或胺的缩合反应合成了24种甜菜红素。建立了一种用于鉴定不同甜菜红素种类的高效液相色谱方法。在大规模条件下制备了脯氨酸、多巴胺和γ-氨基丁酸（GABA）-甜菜红素作为代表性甜菜红素，并将它们的1,1 -二苯基 - 2 - 苦基肼自由基清除活性与已知抗氧化剂的活性进行了比较。GABA -甜菜红素表现出相对较低的活性，而多巴胺 -甜菜红素具有与红色素甜菜苷和花青素矢车菊素3 -葡萄糖苷相似的活性。脯氨酸 -甜菜红素在三种合成化合物中具有最高的活性，并且与黄酮类槲皮素相似。
