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Correlation between Chlorophyll and Chlorogenic Acid Content in Tobacco Leaves ¹

^a Department of Agronomy, University of Kentucky, Lexington, Kentucky 40506

A positive correlation (r = 0.75, P < 0.01) was obtained between chlorophyll and chlorogenic acid content in the seedling leaves of burley and dark tobaccos. The dark tobaccos contained significantly higher concentrations of both constituents than the burleys. Such a correlation also occurred in a cytoplasmic mutant of chlorophyll-variegated tobacco when the green and yellow laminae were compared. In addition, the activity of phenylalanine ammonia-lyase and polyphenol-oxidase was higher in the green lamina than in the yellow tissue, which coincided with quantitative distribution of chlorogenic acid. Chlorophyll deficiency induced by streptomycin in tobacco seedlings resulted in a progressive decrease in chlorogenic acid content. However, an interruption of streptomycin treatment provoked accumulation of the two compounds. Dark-grown seedlings showed an increase in the content of chlorophyll and chlorogenic acid upon illumination. Incorporation of L-phenylalanine-U-¹⁴C into chlorogenic acid during leaf greening was drastically reduced owing to the presence of phenylpyruvate; the latter compound is a possible by-product of chlorophyll biosynthesis. This phenomenon was also evident with light-grown leaves. Results suggest that in addition to phenylalanine ammonia-lyase as a key enzyme regulating chlorogenic acid biosynthesis, an alternative pathway involving the conversion of phenylpyruvate to cinnamate may be functional in tobacco leaves. This pathway may bear importance as to higher chlorogenic acid content in dark tobaccos than in burleys.