title: Zoosporicidal activity of polyflavonoid tannin identified in Lannea coromandelica stem bark against phytopathogenic oomycete Aphanomyces cochlioides.
abstract: In a survey of nonhost plant secondary metabolites regulating motility and viability of zoospores of the Aphanomyces cochlioides, we found that stem bark extracts of Lannea coromandelica remarkably inhibited motility of zoospores followed by lysis. Bioassay-guided fractionation and chemical characterization of Lannea extracts by MALDI-TOF-MS revealed that the active constituents were angular type polyflavonoid tannins. Commercial polyflavonoid tannins, Quebracho and Mimosa, also showed identical zoosporicidal activity. Against zoospores, the motility-inhibiting and lytic activities were more pronounced in Lannea extracts (MIC 0.1 microg/mL) than in Quebracho (MIC 0.5 microg/mL) and Mimosa (MIC 0.5 microg/mL). Scanning electron microscopic observation visualized that both Lannea and commercial tannins caused lysis of cell membrane followed by fragmentation of cellular materials. Naturally occurring polyflavonoid tannin merits further study as potential zoospore regulating agent or as lead compound. To the best of our knowledge, this is the first report of zoosporicidal activity of natural polyflavonoid tannins against an oomycete phytopathogen.
authors.affiliation: Laboratory of Ecological Chemistry, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita-Ku, Sapporo 060-8589, Japan.
authors.forename: Md Tofazzal
authors.initials: MT
authors.lastname: Islam
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Ito
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Sakasai
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tahara
mesh_terms: D027926:Anacardiaceae / Q000737:chemistry*; D047348:Hydrolyzable Tannins / Q000032:analysis* / Q000494:pharmacology*; D008855:Microscopy, Electron, Scanning; D009868:Oomycetes / Q000187:drug effects*; D024301:Plant Bark / Q000737:chemistry*; D010936:Plant Extracts; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013170:Spores / Q000187:drug effects / Q000648:ultrastructure
chemical_list: D047348:Hydrolyzable Tannins; D010936:Plant Extracts