Extractives of Quercus crispula sapwood infected by the pathogenic fungus Raffaelea quercivora II: isolation and identification of phenolic compounds from infected sapwood

There has been a mass mortality of oak trees in the area along the coast of the Japan Sea. This phenomenon is caused by the ambrosia beetle Platypus quercivorus, which carries the ambrosia fungus Raffaelea quercivora. Extractives of a necrotic brownish coloration formed in the infected sapwood of Quercus crispula were investigated. The methanol extract of the damaged sapwood of Q. crispula was concentrated in vacuo and centrifuged to yield precipitates and the supernatant. The precipitates were subjected to Sephadex LH-20 column chromatography and preparative HPLC to describe a novel ellagic acid derivative (1). The 10 % methanol water-soluble part of the supernatant was subjected to medium-pressure ODS column chromatography and preparative HPLC, respectively, to analyze a known lignan (2). Sulfuric acid hydrolysis of (1) yielded an ellagic acid and a gallic acid. NMR and LC-TOF/MS indicated that an ellagic acid and a gallic acid bonded to a xylose with glycosidic and ester bonds, respectively. Compound (1) was identified as 4,5-dihydroxy-6-(3,7,8–trihydroxy-5,10-dihydro–chromeno[5,4,3-cde]chromen-2-yloxy)-tetrahydro-pyran-3-yl ester, and compound (2) was identified as (–)-lyoniresinol. The presence of (–)-lyoniresinol from damaged sapwood indicated that infection of R. quercivora may cause the formation of a pseudo-heartwood in the sapwood of Q. crispula.