Isolation and Characterization of Two Aucuparin-Related Phytoalexins from Photinia glabra Maxim.

Two kinds of biphenyl phytoalexins accumulated in leaves of Photinia glabra Maxim (Rosaceae) in response to inoculation with spores of Entomosporium mespili, a pathogen of P. glabra, or to treatment with 10-4M HgCl2. The phytoalexins were identified as 2'-methoxyaucuparin and 4'-methoxyaucuparin. The contents of 2'-methoxyaucuparin and 4'-methoxyaucuparin were 3.578 and 1.233μg/g of leaf (fresh weight), respectively, 4 days after the inoculation with spores of E. mespili, whereas their contents in the uninoculated leaf were minute. The two phytoalexins exhibited toxicity to Pestalotia photiniae, a pathogenic fungus to P. glabra, and to Botrytis cinerea and Cochliobolus miyabeanus, the non-pathogens. The toxicity of 4'-methoxyaucuparin to P. photiniae and Botrytis cinerea was higher than that of 2'-methoxyaucuparin.