VIEW ARTICLE

Physiology and Biochemistry

Demethylmedicarpin, a Product Formed from Medicarpin by Colletotrichum coccodes. Verna J. Higgins, Department of Botany, University of Toronto, Toronto, Canada M5S 1A1; John L. Ingham, Phytochemical Unit, Department of Botany, University of Reading, Reading RG6 2AS, England. Phytopathology 71:800-803. Accepted for publication 30 December 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-800.

The structure and antifungal activity of a product formed from medicarpin (3-hydroxy-9-methoxypterocarpan) by the tomato pathogen, Colletotrichum coccodes (= C. phomoides), was reinvestigated. The compound was identified as demethylmedicarpin (3,9-dihydroxypterocar-pan) hereafter called CP-I) by ultraviolet, mass, and nuclear magnetic resonance spectroscopy; by chromatographic comparison with authentic material; by methylation, which yielded homopterocarpin (3,9-dimethoxypterocarpan); and by formation of the expected diacetoxy derivative upon acetylation. Contrary to an earlier report, CP-I was considerably less inhibitory than medicarpin in bioassays to test its effects on spore germination, germ tube elongation, and mycelial growth of C. coccodes. Tests with the vital stain fluorescein diacetate also confirmed that the effect of CP-I on the metabolic activity of growing germ tubes was less severe than that of medicarpin. Maackiain (3-hydroxy-8,9-methylenedioxy-pterocarpan) and homopterocarpin did not appear to be metabolized when incubated with C. coccodes under the conditions used for the conversion of medicarpin.