Takayuki Suga

Endogenous pine wood nematicidal substances in pines, Pinus massoniana, P. strobus and P. palustris

Abstract The presence of the repellents and nematicides to the pine wood nematode, Bursaphelenchus xylophilus, was found in the heartwood and bark of Pinus massoniana, P. strobus and P. palustris, which have a resistance to the pine wood nematode. The heartwood of P. massoniana contained a repellent, α-humulene and two nematicidal substances, pinosylvin monomethylether (PSM) and (−)-nortrachelogenin for the nematode. The bark of the pine contained two nematicides, methyl ferulate and (+)-pinoresinol. PSM, which showed the highest nematicidal activity (LD50 was 4 ppm), was also contained in the heartwood of P. strobus and the heartwood and bark of P. palustris. The resistance of these pines to the pine wood nematode is considered to be attributed to the presence of these endogenously defending substances. Further, the relationship between the structure and the nematicidal activity was elucidated for PSM and methyl ferulate. Moreover, PSM showed little anti-acetylcholinesterase activity.

Geranyl diphosphate synthase in leaves of Pelargonium roseum

Abstract A chain-length-specific geranyl diphosphate synthase was detected in leaves of Pelargonium roseum. The enzyme systems, farnesyl diphosphate synthase [EC 2.5.1.1], geranylgeranyl diphosphate synthase and isopentenyl diphosphate isomerase [EC 5.3.2.2], were also detected. Furthermore, geranyl diphosphate synthase was separated from farnesyl diphosphate synthase by hydrophobic chromatography on Butyl-Toyopearl 650. This separation demonstrates that there are two specific syntheses, geranyl diphosphate synthase and farnesyl diphosphate synthase, in this higher plant. The geranyl diphosphate synthase was localized in a subcellular membrane fraction rather than in the soluble fraction. The synthase was activated by Mn2+ rather than Mg2+.

Biologically active labdane-type diterpene glycosides from the root-stalks of Gleichenia japonica

A glycoside showing a strong growth inhibition of lettuce was isolated from the root-stalks of Gleichenia japonica and its structure was established to be the 3-O-alpha-rhamnopyranosyl-(1----2)-beta-glucopyranoside of 13-O-alpha-rhamnopyranosyl-(+)-3 beta-hydroxymanool. In addition, two related glycosides were also isolated and they were characterized as the 3-O-beta-fucopyranosyl-(1----3)-alpha-rhamnopyranosyl-(1----2)-beta- glucopyranoside of 13-O-alpha-rhamnopyranosyl-(+)-3 beta-hydroxymanool and the 13-O-rhamnopyranoside of the same diterpene alcohol. The diterpene alcohol accelerated the growth of lettuce.

Demonstration of geranyl diphosphate synthase in several higher plants

Abstract A chain-length-specific geranyl diphosphate synthase was found in leaves of several higher dicotyledon plants. Geranyl diphosphate synthase could be separated from farnesyl diphosphate synthase by hydrophobic chromatography on Butyl-Toyopearl 650.

Characterization of two enone reductases from Nicotiana tabacum cell cultures

Abstract Two enone reductases, designated Reductase-I and -II, were isolated from Nicotiana tabacum cell cultures. These two reductases have different M r s, pH optimum, coenzyme requirement and substrate specificity. Reductase-I catalyses the reduction of the endocyclic Cue5f8C double bond of enones which bear a hydrogen-substituent at the position β to the carbonyl, while Reductase-II catalyses the reduction of the exocyclic Cue5f8C double bond of enones.

Biologically active clerodane-type diterpene alcohol and its glycosides from the root-stalks of ferns

A diterpene alcohol showing a growth inhibition of lettuce was isolated from the root-stalks of Dicranopteris pedata and Gleichenia japonica. Its structure was determined to be (6S,13S)-cleroda-3,14-diene-6,13-diol 1, an aglycone of the two glycosides previously isolated from G. japonica; the chirality at both C-6 and C-13 was assigned as S by application of the β-D-glucosylation-shift rule and by measurement of 13C NMR chemical shifts, respectively. Further, two glycosides showing growth inhibition were also isolated from D. pedata and they were characterised as the 13-O-β-L-fucopyranosyl-(1 → 2)-α-L-rhamnopyranoside 3 and 13-O-α-L-fuoopyranosyl-(1 → 2)-[α-L-rhamnopyranosyl-(1 → 3)]-α-L-rhamnopyranoside 4 of the diterpene alcohol; the above assignment of the chirality at C-13 was established by measurement of nuclear Overhauser enhancement for the trisaccharide. In addition, a glycoside showing growth acceleration was also isolated and its structure was determined to be (6S,13S)-13-O-β-L-fucopyranosyl-6-O-α-L-rhamnopyranosylcleroda-3,14-diene-6,13-diol 2.

Absolute configurations of pittosporatobiraside A and B from Pittosporum tobira

Abstract The absolute configuration at C-12 of pittosporatobiraside A and B isolated from the leaves of Pittosporum tobira was determined to be S on the basis of the exciton chirality of their dibenzoate derivative. The structures of the two glycosides were thus established to be (1 S ,9 S ,10 S ,11 S ,12 S ,14 R ,16 R )-12-[( Z )-2-methyl-1-oxo-2-butenyl]-6,14-dimethyl-2-methylene-9-(1-methylethyl)-15,17-dioxatricyclo[8.7.0.0 11,16 ]heptadec-5-en-13-one and (1 S ,9 S ,10 S ,11 S ,12 S ,14 R ,16 R )-12-(3-methyl-1-oxo-2-butenyl)-6,14-dimethyl-2-methylene-9-(1-methylethyl)-15,17-dioxatricyclo [8.7.0.0 11,16 ]heptadec-5-en-13-one, respectively.

Cerebrosides of frog brain. Structure of the ceramide part of the cerebrosides

Twelve cerebrosides were isolated from the brain tissues of the bullfrog (Rana catesbeiana) and they were characterised as 1-o-β-D-galactopyranosyl ceramides. On the basis of chemical and spectral evidence, the ceramide parts of six of them were found to be composed of a sphingosine as a long-chain base and six fatty acids consisting of C18:0, C22:1, C24:1 and their 2-hydroxy derivatives. The ceramide parts of the others were found to be composed of a dihydrosphingosine and the six fatty acids. The configurations at C-2 and C-3 of the two long-chain bases were determined to be S and R, respectively, on the basis of the NMR spectra of their acetates and the exciton chiralities of the benzoate-benzamide derivatives. Further, the chiral centre of the three 2-hydroxy fatty acids was determined to be R in all cases by means of CD measurements. A different distribution of the cerebrosides was seen among the hemisphere, diencephalon and mixed tissue from the optic lobe, cerebellum and medulla oblongata of the brain.

Regioselective hydrogen elimination from the 10-methyl group of geranyl diphosphate in the biological formation of the 8(9)-double bond of limonene

The biological formation of the 8(9)-double bond of both (4S)-(–)- and (4R)-(+)-limonenes in Mentha spicata and Citrus unshiu is found to be stereospecifically controlled by the regioselective elimination of a hydrogen atom from the 10-methyl group, i.e. the Z-methyl group, of geranyl diphosphate.

Facilitation of diphosphate group elimination from geranyl diphosphate by magnesium ion chelation in cyclic monoterpenoid biosynthesis

The role of divalent metal ions in the biosynthesis of cyclic monoterpenoids has been investigated by an analysis of the 31P and 13C NMR spectra of geranyl diphosphate (GPP) in the presence and in the absence of Mg2+. This study revealed that Mg2+ binds to the diphosphate moiety of GPP in the ratio of 1 : 1, equidistantly from both phosphorus atoms, and that Mg2+ chelation weakens the C(1 )–O(5) bond of GPP, facilitating elimination of the diphosphate group.