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Separation and Identification of Two Pterocarpanoid Phytoalexins Produced by Red Clover Leaves. Verna J. Higgins, University of Toronto, Toronto 181, Ontario; D. G. Smith, National Research Council of Canada, Atlantic Regional Laboratory, Halifax, Nova Scotia. Phytopathology 62:235-238. Accepted for publication 7 September 1971. DOI: 10.1094/Phyto-62-235.

Two pterocarpanoid compounds produced by red clover (Trifolium pratense) leaves in response to inoculation with Helminthosporium turcicum were separated by thin-layer chromatography. They were identified as 3-hydroxy-9-methoxypterocarpan (medicarpin) and 3-hydroxy-8, 9-methylenedioxypterocarpan (maackiain) on the basis of ultraviolet, infra-red, and nuclear magnetic resonance spectra. The quantities of medicarpin and maackiain produced by several red clover cultivars appeared sufficient to adversely affect growth of H. turcicum on clover leaves.