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首页> 外文期刊>Chemistry: A European journal >Identification of 7,4 '-dihydroxy-5-methoxyflavylium in 'Dragon's blood': To be or not to be an anthocyanin
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Identification of 7,4 '-dihydroxy-5-methoxyflavylium in 'Dragon's blood': To be or not to be an anthocyanin

机译：鉴定“龙血”中的7,4'-二羟基-5-甲氧基黄酮：是否为花青素

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摘要

The compound 7,4'-dihydroxy-5-methoxyflavylium (dracoflavylium) was identified as the major red colorant in samples of the resin "dragon's blood", extracted from the tree Dracaena draco. The complex network of reversible chemical reactions that dracoflavylium undergoes in aqueous solution is fully described; for the first time, all the equilibrium constants that enable a complete characterisation of the system have been obtained (K'(a)=1.6 x 10(-4), K-a1 = 1.0 x 10(-4), K-a2 = 3.2 x 10(-8), K-Ct1 = 1.0 x 10(-7), K-Ct2 = 1.3 x 10(-10)). It is concluded that the red colour is due to a stable quinoid base, A, which is the major species at pH 4-7. It is further shown that this compound does not fit the commonly accepted definitions of anthocyanidin nor 3-deoxyanthocyanidin. Similarly to synthetic flavylium salts, the natural compound 7,4'-dihydroxy-5-methoxyflavylium gives rise to several species (multistate system) reversibly interconverted by external stimuli, such as pH.
机译：从树龙血树中提取的树脂“龙血”样品中，化合物7,4'-二羟基-5-甲氧基黄酮（dracoflavylium）被鉴定为主要的红色着色剂。德拉科黄酮在水溶液中经历的可逆化学反应的复杂网络已得到充分描述;首次获得了能够完全表征系统的所有平衡常数（K'（a）= 1.6 x 10（-4），K-a1 = 1.0 x 10（-4），K-a2 = 3.2 x 10（-8），K-Ct1 = 1.0 x 10（-7），K-Ct2 = 1.3 x 10（-10））。结论是红色是由于稳定的醌型碱A所致，它是pH值为4-7时的主要物种。进一步表明，该化合物不符合花青素或3-脱氧花青素的普遍接受的定义。类似于合成的黄酮盐，天然化合物7,4'-二羟基-5-甲氧基黄酮产生多种物质（多态系统），这些物质可通过外部刺激（例如pH）可逆地相互转换。

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