Distribution and utilization of chlorogenic acid in Coffea seedlings

Ripe coffee seeds (Coffea arabica L.) contain large quantities of the purine alkaloid caffeine and the depside chlorogenic acid (5-O-caffeoyl-quinic acid). Directly after germination, both compounds were recovered almost exclusively in the cotyledons and surrounding endosperm and hardly at all in the hypocotyl and root of coffee seedlings. During the first 10 weeks of development, the cotyledons invaded the endosperm and expanded. The caffeine content in the developing cotyledons changed little, but the chlorogenic acid content dropped to one-third of the original level. The loss of chlorogenic acid was not recovered in the other organs of the seedling. The drop in chlorogenic acid content coincided with an increase in the amount of cell wall-bound phenolic polymers in the developing cotyledons, which could be extracted after thioglycolic acid derivatization. In the developing cotyledons, phenylalanine ammonia lyase (PAL) activity was hardly detectable. These results suggest that the chlorogenic acid stored in coffee seeds is used for the deposition of phenolic polymers, presumably lignin, in cotyledonary cell walls during expansion. The situation in cotyledons was found to be in marked contrast to that in foliage leaflets, in which PAL activity was 900-fold higher than in cotyledons. In the leaflets, both chlorogenic acid and caffeine accumulated continuously during leaf expansion.