title: Identification of a novel casbane-type diterpene phytoalexin, ent-10-oxodepressin, from rice leaves.
abstract: A 70% methanol extract of UV-irradiated rice leaves (400 g) was separated by chromatographic methods to give UV-induced compound 1 (2.1 mg) which showed a possible molecular ion at m/z 300 in the GC/MS analysis. Its structure was determined by NMR and MS methods. The 1H- and 13C-NMR spectra of 1 were identical to those of 10-oxodepressin (2), a casbane-type diterpene derived from the soft coral, Sinularia depressa. The specific rotation of 1 was positive, whereas that of 2 was negative. We therefore established 1 as ent-10-oxodepressin. The accumulation of 1 was also induced by an inoculation of the rice blast fungus. Compound 1 inhibited spore germination (IC50 30 ppm) and germ tube growth (IC50 10 ppm) of the rice blast fungus. We thus concluded that 1 was a novel rice phytoalexin.
authors.affiliation: College of Agriculture, Ibaraki University, Ibaraki, Japan.
authors.forename: Yasuno
authors.initials: Y
authors.lastname: Inoue
authors.forename: Miki
authors.initials: M
authors.lastname: Sakai
authors.forename: Qun
authors.initials: Q
authors.lastname: Yao
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Tanimoto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Toshima
authors.forename: Morifumi
authors.initials: M
authors.lastname: Hasegawa
mesh_terms: D000935:Antifungal Agents / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D004224:Diterpenes / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D020082:Magnaporthe / Q000187:drug effects / Q000502:physiology; D012275:Oryza / Q000737:chemistry* / Q000378:metabolism / Q000382:microbiology / Q000528:radiation effects; D018515:Plant Leaves / Q000737:chemistry* / Q000378:metabolism / Q000382:microbiology / Q000528:radiation effects; D012717:Sesquiterpenes / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D014466:Ultraviolet Rays; D000094162:Phytoalexins
chemical_list: D000935:Antifungal Agents; D004224:Diterpenes; D012717:Sesquiterpenes; C584527:ent-10-oxodepressin; D000094162:Phytoalexins