21 アントシアニン色素の自己会合 : 証明と構造

概要

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Since the work of Willstatter, it has been known that anthocyanins are responsible for a variety of beautiful plant colors. Anthocyanins are generally unstable to form colorless products. Stability and variety of flower coloring have been explained in terms of co-pigmentation with flavones etc and the complexation with metal ions. We report a new concept, the self-association of anthocyanins, for the stabilization and variation of flower color. Naturally occurring anthocyanins associate without any other component in the concentration usually found in the flower petals. The occurrence of the self-association of anthocyanins was evidenced by the following experimental facts; color variation (hypsochromic or bathochromic shift) and appearance of typical exciton coupling circular dichroism with increase of anthocyanin concentration. Hydration rate (k) of quinonoidal bases and hydration constant (K_h) of flavylium ions toward the corresponding colorless pseudobases are also presented as the evidence. Vertical stacking structure is proposed for the self-aggregation of anthocyanins on the basis of PMR shift data due to the ring current effect of anthocyanin nuclei. Thus, origin of the anomalous CD comes from the chiroptical stacking of anthocyanin molecules. Such a stacking structure of cyanin quinonoidal base was also suggested by calculation of the exciton chirality method.
天然有機化合物討論会の論文
1981-09-10