VIEW ARTICLE

Postharvest Pathology and Mycotoxins

Chemical Structure of Preinhibitin in Citrus Against Citrus Stem-End Rot. Yasuo Homma, RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama, 351-01 Japan; Tomihiko Ohsawa(2), Yutaka Arimoto(3), and Hiroharu Takahashi(4). (2)(3)RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama, 351-01 Japan; (4)National Institute of Agro-Environmental Sciences, Ministry of Agriculture, Foresty and Fishery, Yatabe-Machi, Tsukuba, Ibaraki 305 Japan. Phytopathology 82:310-314. Accepted for publication 7 October 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-310.

When pedicels of Satsuma mandarin fruits on trees were inoculated with Diaporthe citri and then harvested in early December and stored at room temperature, stem-end rot was not observed until late February. Numerous crystals were distributed in the tissues around the stem button. The dissolved crystals inhibited conidial germination and germ-tube elongation of D. citri. The substance, referred to as the preinhibitin, was hydrolyzed by refluxing in ethyl alcohol-hydrochloric acid, 10:1, for 18 h. The resinous material obtained from the ether-soluble fraction was purified by repeated preparative thin-layer chromatography on silica gel to yield pale yellow crystals. This compound was identified as a flavanone, hesperetin. The original compound proved to be a glycoside with hesperetin as the aglycon. The preinhibitin was identified as hesperetin-7-rhamnoglucoside or hesperidin.