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Inhibition of Wood-Rotting Fungi by Ellagitannins in the Heartwood of Quercus alba. John H. Hart, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48823; W. E. Hillis, Forest Products Laboratory, Division of Applied Chemistry, CSIRO, South Melbourne, Victoria 3205, Australia. Phytopathology 62:620-626. Accepted for publication 12 January 1972. DOI: 10.1094/Phyto-62-620.

Successive extraction of the heartwood of white oak (Quercus alba) with a series of solvents of increasing polarity revealed that fungistatic components were largely contained in the aqueous acetone extract. Both Polyporus versicolor and Poria monticola were inhibited in vitro by 1,000 ppm of the aqueous acetone extract. When this extract was impregnated into the normally decay-susceptible sapwood of cottonwood (Populus deltoides) at approximately the same concentration as that found in white oak heartwood, subsequent decay by P. monticola was reduced by 44%, but decay by P. versicolor was unaffected. Fractionation of the aqueous acetone extract followed by in vitro bioassays showed that the inhibitory compounds were water-soluble tannins. Chemical characterization by RF values, chromogenic sprays, and hydrolysis demonstrated the toxic materials to be solely ellagitannins, the fungistatic effects of which were negated by the addition of polyvinyl pyrrolidone (PVP) or Tween 80 (polyoxyethylene sorbitan monooleate) to the growth medium. These data indicate that the heartwood of white oak is not decayed by P. monticola because certain ellagitannins are present. These compounds are thought to inhibit certain fungal proteins owing to their protein-binding capacity.