Metal Complex Pigment Involved in the Blue Sepal Color Development of Hydrangea

详细信息    查看全文

• 作者：Kin-ichi Oyama ; Tomomi Yamada ; Daisuke Ito ; Tadao Kondo ; Kumi Yoshida
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2015
• 出版时间：September 9, 2015
• 年：2015
• 卷：63
• 期：35
• 页码：7630-7635
• 全文大小：337K
• ISSN：1520-5118

文摘

Anthocyanins exhibit various vivid colors from red through purple to blue and are potential sources of food colorants. However, their usage is restricted because of their instability, especially as a blue colorant. The blue sepal color of Hydrangea macrophylla is due to a metal complex named 鈥渉ydrangea-blue complex鈥?composed of delphinidin 3-O-glucoside, 1, 5-O-caffeoylquinic acid, 2, and/or 5-O-p-coumaroylquinic acid, 3, as copigments, and Al³⁺ in aqueous solution at approximately pH 4.0. However, the ratio of each component ins not stoichiometric, but is fluctuates within a certain range. The hydrangea-blue complex exists only in aqueous solution, exhibiting a stable blue color, but attempts at crystallization have failed; therefore, the structure remains obscure. To clarify the basis of the character of the hydrangea-blue pigment and to obtain its structural information, we studied the mixing conditions to reconstruct the same blue color as observed in the sepals. In highly concentrated sodium acetate buffer (6 M, pH 4.0) we could measure ¹H NMR of both the hydrangea-blue complex composed of 1 (5 mM), 2 (10 mM), and Al³⁺ (10 mM) and a simple 1鈥揂l³⁺ complex. We also recorded the spectra of complexes composed with structurally different anthocyanins and copigments. Comparison of those signals indicated that in the hydrangea-blue complex 1 might be under equilibrium between chelating and nonchelating structures having an interaction with 2.