81 柿の脱渋機構の化学的解明(ポスター発表の部)

概要

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Astringent cultivars of persimmon (Diospyros kaki) are only edible after treatment with alcohol vapor, warm water or carbon dioxide gas, removing astringency. In order to study the chemical mechanism for de-astringency of the fruit, we have developed a new method for thiolysis of proanthocyanidins using 2-mercaptoethanol and hydrochloric acid in aqueous medium, and applied the method to degradation of insolubilized proanthocyanidin which remained in plant debris after extraction with aqueous acetone. Thiolysis of plant debris of the fruit treated with 35% EtOH yielded fourteen thioethers. Among them, 9-14 unequivocally shows that acetaldehyde participates in the de-astringency process by linking two phloroglucinol rings of proanthocyanidin molecules. Furthermore, from the fruit treated with ethanol-d_6, thioethers 9d and 9e were obtained, indicating that the C_2 unit originated from acetaldehyde which generated by oxidation of ethanol added externally. Similar examination on mature fruits of banana and grape also showed the presence of insolubilized proanthocyanidin. HPLC analyses of thiolysates from plant debris of the flesh suggested that immobilization of proanthocyanidin by condensation with acetaldehyde also occur in these fruits.
天然有機化合物討論会の論文
1993-09-10