Yukiharu Fukushi

Shizukaol A, A sesquiterpene dimer from Chloranthus japonicus

Abstract A novel dimeric sesquiterpene consisted of two lindenane (modified eudesmane) units was isolated from roots of Chloranthus japonicus . The structure was elucidated by 1D and 2D NMR analyses and by chemical methods.

An antifungal compound from roots of Welsh onion

A novel antifungal compound, fistulosin (octadecyl 3-hydroxyindole), was isolated from roots of Welsh onion (Allium fistulosum L.), and its structure was elucidated by spectroscopic means. This compound showed high activity against Fusarium oxysporum primarily inhibiting protein synthesis.

Highly oxidized cuparene-type sesquiterpenes from a mycelial culture of Flammulina velutipes.

Cuparene-type sesquiterpenes were isolated from a culture broth of Flammulina velutipes (Curt.:Fr.) Sing. Using spectroscopic methods (HR-MS, 1H and 13C NMR, and 2D NMR, spectroscopy), their structures were determined to be 2,3,4,5-tetrahydro-2,7-dihydroxy-5,8,10,10-tetramethyl-2,5-methano-1- benzoxepin and 5-methyl-2-(3-oxo-1,2,2-trimethylcyclopentyl)benzoquinone. Both showed antimicrobial activity against Cladosporium herharum and Bacillus subtilis.

A new method for establishment of absolute configurations of secondary alcohols by NMR spectroscopy

Abstract Axially chiral 2′-methoxy-1,1′-binaphthyl-2- carboxylic acid (MBNC, 2 ) and 2-(2′-methoxy-1′-naphthyl)-3,5-dichlorobenzoic acid (MNCB, 3 ) were used as chiral derivatizing agents to determine absolute configurations of secondary alcohols by 1 H and 13 C NMR spectroscopy.

Enzymatic nitration of phytophenolics: evidence for peroxynitrite‐independent nitration of plant secondary metabolites

Peroxynitrite (ONOO−), a reactive nitrogen species, is capable of nitrating tyrosine residue of proteins. Here we show in vitro evidence that plant phenolic compounds can also be nitrated by an ONOO−‐independent mechanism. In the presence of NaNO2, H2O2, and horseradish peroxidase (HRP), monophenolic p‐coumaric acid (p‐CA, 4‐hydroxycinnamic acid) was nitrated to form 4‐hydroxy‐3‐nitrocinnamic acid. The reaction was completely inhibited by KCN, an inhibitor for HRP. The antioxidant ascorbate suppressed p‐CA nitration and its suppression time depended strongly on ascorbate concentration. We conclude that nitrogen dioxide radical (NO2 • ), but not ONOO−, produced by a guaiacol peroxidase is the intermediate for phytophenolic nitration.

Fungitoxic alkaloids from Hokkaido Corydalis species

Abstract Two species of the genus Corydalis (C. incisa and C. ambigua) were phytochemically studied for their fungitoxic alkaloids. Thirteen alkaloids were isolated and identified by spectroscopic methods including mass and NMR techniques. Compounds 1 (corynoline) and 2 (acetylcorynoline) were found to be the main active compounds. The new compound 3 (named coryincine) has no fungitoxic activity. Structure–activity relationships among compounds 1–3 are discussed.

Isoflavonoid glycosides from eriosema tuberosum

Abstract Five isoflavonoid glycosides together with the corresponding aglycones have been isolated from the n-BuOH-soluble fraction of a methanol extract of the roots of Eriosema tuberosum. One compound is new and its structure has been established by spectroscopic analyses and chemical methods as 5-O-methylgenistein 7-O-β- d -apiofuranosyl-(1 → 6)-O-β- d -glucopyranoside.

Antimicrobial stress compounds from Hypochoeris radicata

The exudates of Hypochoeris radicata leaves stressed with cupric chloride afforded two eudesmane- and guaiane-type sesquiterpenes, and two alkenals, (2E,4E)-6-hydroxyhexadienal and (2E,4E)-hexadienedial (mucondialdehyde). Their structures were determined by spectroscopic and synthetic methods.

NMR determination of the absolute configuration of cyclic chiral alkenes

Abstract By the use of a new axially chiral reagent, 2′-methoxy-1,1′-binaphthalene-2-carbohydroximoyl chloride (MBCC), chiral cyclic alkenes were stereoselectively derivatized into 4,5-dihydroisoxazoles. NOEs were observed between the protons of the reagent moiety and those of the alkene moiety in cycloadducts. The absolute configuration of the original alkenes was unambiguously determined by the NOE correlation.

A new method for fast isolation of insect antifeedant compounds from complex mixtures.

Bioassay-guided isolation of bioactive natural substances requires monitoring of all fractionation and purification steps using a bioassay system. This is often a long and tedious process, especially with insect feeding bioassays. We report here a new method, based on the principle of bioautography, for a quick isolation of insect antifeedant compounds. TLC plates, after development, are coated with a thin layer of artificial diet and fed toSpodoptera litura larvae. The location of uneaten areas is then compared with theRfvalues of the TLC spots, in order to determine rapidly the active fractions. This methods allows for a very fast determination of the most active antifeedant compounds in a complex mixture and considerably speeds up the isolation process. This new method was successfully applied in the study of antifeedant activity of several plant samples, and results are presented here for a model plant,Skimmia japonica (Rutaceae). Using this new method, the compounds responsible for the feeding-deterrent activity, three furanocoumarins (bergapten, xanthotoxin, and oxypeucedanin), were quickly and efficiently identified.