Analytical study of ipomeamarone & chlorogenic acid alterations in sweet potato roots infected by Ceratocystis fimbriata.

Several metabolic alterations have been studied, from biochemical and pathological viewpoints, in sweet potato roots infected by the black rot fungus, Ceratocystis finbriata (2, 11, 13), among which the formation of ipomeamarone is of particular interest. Because this substance is a unique furanoterpenoid produced by host tissues in response to infection, and because it has remarkable biological properties, such as uncoupling and antipathogenic actions, elucidation of its biosynthetic mechanism would be of great value for the further study of terpene formation and of the host-parasite relationship. Furthermore, an increase of polyphenolic substances, e.g., chlorogenic acid, has been commonly observed in diseased plants (6, 10, 14), and some workers have implied that these play an important role in the defense mechanism, although contradictory evidence has been presented (5, 11). We have undertaken an analytical study of ipomeamarone and chlorogenic acid (3). However, recent chromatographic evidence (1) showing a concurrent formation of many ipomeamarone-like terpenoids in injured root tissues indicates the necessity of a more critical analysis of such metabolites in host tisstues. The present paper deals with the quantitative analyses of ipomeamarone and chlorogenic acid in the infected root tissues of resistant and susceptible sweet potato varieties, and their possible role in the defense mechanism.