Mitsuo Takasugi

Brassicanal C and two dioxindoles from cabbage

Abstract Brassicanal C, a new sulphur-containing phytoalexin, and two dioxindoles were isolated from cabbage inoculated with Pseudomonas cichorii. Brassicanal C was shown to possess a unique sulphinate structure on the basis of spectroscopic data and optical activity. One of the dioxindoles, dioxibrassinin, appears structurally to be a possible precursor to spirobrassinin.

Psoralen and other linear furanocoumarins as phytoalexins in Glehnia littoralis

Inoculation of Glehnia littoralis root slices with Pseudomonas cichorii induced the production of four linear furanocoumarin phytoalexins, psoralen, xanthotoxin, bergapten and demethylsuberosin, of which the former three have been reported as constituents of the crude drug Glehnia root. A time-course study on the respective P. cichorri-inoculated, UV-irradiated and non-irradiated root slices showed greatly increasing concentrations of the furanocoumarins after stress treatment. Psoralen, xanthotoxin and bergapten in the crude drug were considered, at least in part, to be stress metabolites produced during processing.

NEW SYNTHESES OF INDOLE PHYTOALEXINS AND RELATED COMPOUNDS

Abstract Synthesis of indole phytoalexins brassinin, brassitin, cyclobrassinin and related compounds via 3-aminomethylindole and its 1-substituted derivatives obtained by nickel boride catalyzed reduction of corresponding aldoximes with sodium borohydride and via [1-( t -butoxycarbonyl)-indol-3-yl]methyl isothiocyanate, the first stable derivative of indol-3-ylmethyl isothiocyanate is described. Antifungal activity of the prepared compounds was examined by using the fungus Bipolaris leersiae by t.l.c. bioassay and quantitative screening was carried out with the selected compounds.

Three sulphur-containing stress metabolites from Japanese radish☆

Abstract Three new brassinin related stress metabolites, named brassitin, N-methoxyspirobrassinol methyl ether and N-methoxyspirobrassinol, were isolated from the Japanese radish ‘Daikon’ (Raphanus sativus var. hortensis) after inoculation with Pseudomonas cichorii. Their structures have been established on the basis of spectroscopic data and chemical reactions. N-Methoxyspirobrassinol has an unusual hemi-aminal structure, and occurs as a mixture of diastereomers. The occurrence of N-methoxyspirobrassinol methyl ether and N-methoxyspirobrassinol suggests the involvement of oxidized intermediates in the biosynthesis from brassinin to spirobrassinin

Antifungal compounds from Dioscorea batatas inoculated with Pseudomonas cichorii

Abstract An induced and six preformed antifungal compounds were isolated from Chinese yam ( Dioscorea batatas ) inoculated with the bacterium Pseudomonas cichorii . The induced compound, a phytoalexin, was identified as dihydropinosylvin. The preformed compounds were characterized as oxygenated bibenzyls and phenanthrenes.

Structures of moracins E, F, G, and H, new phytoalexins from diseased mulberry

Abstract The structures and antifungal activity of four new mulberry phytoalexins, designated as moracins E, F, G, and H, are described.

A guaianolide phytoalexin, cichoralexin, from Cichorium intybus.

Abstract A sesquiterpenoid phytoalexin, cichoralexin was isolated from Cichorium intybus inoculated with Pseudomonas cichorii . Its structure has been elucidated by spectroscopic methods.

Phytoalexins from Brassica (Cruciferae) as oviposition stimulants for the cabbage root fly, Delia radicum

Summary. Bacteria species known to induce the biosynthesis of crucifer-specific phytoalexins have earlier been shown to be associated with Delia flies. Eleven crucifer-specific phytoalexins and related synthetic compounds were applied on surrogate paper leaves and offered to cabbage root flies in oviposition assays. Since three of these compounds (methoxybrassinin, cyclobrassinin, brassitin) proved to be significantly stimulatory whereas the remaining metabolites had no effect, the reaction of the fly appears to be structure-specific. Inactive phytoalexins had no inhibitory effect on oviposition. 100 μg of methoxybrassinin per surrogate leaf was as stimulatory as 0.05 gle (gram leaf equivalent) of a methanolic host-leaf (Brassica oleracea) extract. Thus the three active phytoalexins can explain only part of the activity of host-pant extracts but might induce a preference for infected plants.

Confirmation of the structures of kuwanons G and H (albanins F and G) by partial synthesis

Abstract Conclusive evidence is presented supporting structures 1 and 2 for two natural Diels-Alder adducts isolated from mulberry and designated as kuwanon G (albanin F, moracenin B) and Kuwanon H (albanin G, Moracenin A).

Isolation of three novel sulphur-containing phytoalexins from the chinese cabbage Brassica campestris L. ssp. pekinensis(cruciferae)

Inoculation of Chinese cabbage heads with the bacterium Pseudomonas cichorii induced the production of three major phytoalexins named methoxybrassinin (1), brassinin (2), and cyclobrassinin (3), whose structures have been elucidated on the basis of spectroscopic studies and synthesis.