Turnover and Metabolism of Chlorogenic Acid in Xanthium Leaves and Potato Tubers

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Abstract
The active turnover of chlorogenic acid (3-O-caffeoylquinic acid), a major phenolic component of Xanthium leaves and potato tubers, was demonstrated in these tissues. Pulse-labelling experiments with radioactive L-phenylalanine and trans-cinnamic acid as well as direct feeding experiments with chlorogenic acid-C14 labelled in the caffeoyl moiety were employed in the turnover studies. The rate of turnover is calculated to be on the order of 50 to 100 m[mu]moles/hr./gm fresh weight of tissue. In Xanthium leaves chlorogenic acid is in part converted to an isochloro-genic acid identified by silica gel chromatography as 3,5-di-O-caffeoyl-quinic acid. Radioactivity of the caffeoyl moiety of chlorogenic acid is also incorporated into lignin-like polymers in the leaf. Turnover of chlorogenic acid in tuber tissue is largely accuunted for by the incorporation of the caffeoyl moiety into insoluble polymers in the tissue.