Hiroyuki Kasahara

An insect growth inhibitory lignan from flower buds of Magnolia fargesii

Abstract Bioassay-guided isolation afforded a new lignan, (+)-epimagnolin A, from the flower buds of Magnolia fargesii . This lignan exhibited growth inhibitory activity against larvae of Drosophila melanogaster . The structure of a new lignan was determined on the basis of spectral methods.

Phenolic lignans from flower buds of Magnolia fargesii

Abstract Three phenolic lignans were isolated from flower buds of Magnolia fargesii . One was a new lignan named (+)-de- O -methylmagnolin and the other two were the newly found lignans from this plant, (+)-phillygenin and (+)-pinoresinol. The structures of these lignans were determined by spectroscopic studies. The structure of (+)-magnolin isolated from this plant was also investigated in detail by spectral data.

Current aspects of auxin biosynthesis in plants

Auxin is an important plant hormone essential for many aspects of plant growth and development. Indole-3-acetic acid (IAA) is the most studied auxin in plants, and its biosynthesis pathway has been investigated for over 70 years. Although the complete picture of auxin biosynthesis remains to be elucidated, remarkable progress has been made recently in understanding the mechanism of IAA biosynthesis. Genetic and biochemical studies demonstrate that IAA is mainly synthesized from l-tryptophan (Trp) via indole-3-pyruvate by two-step reactions in Arabidopsis. While IAA is also produced from Trp via indole-3-acetaldoxime in Arabidopsis, this pathway likely plays an auxiliary role in plants of the family Brassicaceae. Recent studies suggest that the Trp-independent pathway is not a major route for IAA biosynthesis, but they reveal an important role for a cytosolic indole synthase in this pathway. In this review, I summarize current views and future prospects of IAA biosynthesis research in plants. Graphical abstract Indole-3-acetic acid (IAA), the most important auxin in plants, is mainly synthesized from l-tryptophan via indole-3-pyruvate (IPA) by the TAA and YUC families in Arabidopsis.

Biotransformation of (+)-magnolin and (+)-yangabin in rat

Abstract The neutral lignans (+)-magnolin and (+)-yangabin, each containing the 2,6-diaryl-3,7-dioxabicyclo [3,3,0]octane skeleton, were administered separately

Biotransformation of lignans: a specific microbial oxidation of (+)-eudesmin and (+)-magnolin by Aspergillus niger

Abstract Biotransformation of the lignans, (+)-eudesmin, (+)-magnolin and (+)-yangabin, by Aspergillus niger has been investigated. (+)-Eudesmin was metabolized and transformed to (+)-de-4′- O -methyleudesmin and (+)-pinoresinol. Additionally, (+)-pinoresinol was examined and oxidized to (+)-5′-hydroxypinoresinol. (+)-Magnolin was transformed to (+)-de- O -methylmagnolin and (+)-de-4′--methyl-5′-hydroxymagnolin. In these metabolic processes, other products were not generated, although (+)-yangabin and (+)-de-4′- O -methyl-5′-hydroxymagnolin were hardly metabolized by this fungus. This suggested that the veratryl and guaiacyl groups of these lignans were possibly metabolized preferentially, with oxidation proceeding predominantly through de- O -methylation at the p -position of veratryl groups. By contrast, 3,4,5-trimethoxyphenyl and 4,5-dihydroxy-3-methoxyphenyl groups of this type of lignan were stable and not attacked by A. niger . The structures of metabolic products were determined by spectroscopic methods as well as by comparison of spectral data with those of known related compounds.

Biotransformation of lignans: Metabolism of (+)-eudesmin and (+)-magnolin in Spodoptera litura

Abstract Biotransformation of the plant lignans, (+)-eudesmin and (+)-magnolin in Spodoptera litura larvae has been investigated. (+)-De-4′-O-methyleudesmin and (+)- de -4′-O- methyleudesmin -4′-O-β- d -glucoside were identified from the (+)-eudesmin-administered larvae faeces, and (+)-de-4″-O-methylmagnolin and (+)- de -4″-O- methylmagnolin -4″-O-β- d -glucoside were from (+)-magnolin-administered, respectively. The metabolic reaction of (+)-eudesmin and (+)-magnolin in Spodoptera litura larvae is de-O-methylation at para-position on veratryl and 3,4,5-trimethoxyl groups followed by glucosylation.

Absolute configuration of 8-O-4′-neolignans from Myristica fragrans

Abstract The absolute configuration of ( + )- erythro -(7 S ,8 R )-Δ 8′ -4,7-dihydroxy-3,3′,5′-trimethoxy-8- O -4′-neolignan and ( − )- erythro -(7 R ,8 S )-Δ 8′ -4,7-dihydroxy-3,3′,5′-trimethoxy-8- O -4′-neolignan was determined by the application of Moshers ( 1 H) method. Furthermore, LiAIH 4 reduction of the MTPA ester of erythro -(7 S ,8 R )-Δ 8′ -4-acetoxy-7-hydroxy-3,3′,5′- trimethoxy-8- O -4′-neolignan afforded ( − )-(8R)- Δ 8′ -4-hydroxy-3,3′,5 t -trimethoxy) -8-O-4′- neolignan , and that of the MTPA ester of erythro -(7 R ,8 S )-Δ 8′ -4-acetoxy-7-hydroxy-3,3′,5′-trimethoxy-8- O -4′-neolignan afforded ( + )-(8 S )-Δ 8′ -4-hydroxy-3,3′,5′-trimethoxy)-8- O -4′-neolignan, respectively.

Microbial oxidation of (+)-epimagnolin a by Aspergillus niger

Abstract Microbial transformation of (+)-epimagnolin A has been investigated using Aspergillus niger . (+)-Epimagnolin A was regioselectively oxidized at the para -methoxyl group of its veratryl group and converted to (+)-de- O -methylepimagnolin A. This metabolic product was then further oxidized at the para -position of its 3,4,5-trimethoxyphenyl group and (+)-de-4′,4″- O -dimethylepimagnolin A was yielded. The structures of the metabolic products were determined by spectroscopic methods, as well as by comparison of spectral data with those of known related compounds.

Antifungal Activities of 8-O-4′-Neolignans from Myristica Fragrans

Abstract Antifungal activity of (±)-erythro-Δ8−4,7-dihydroxy-3,3′,5′-trimethoxy-8-O-4′-neoneolignan derivatives against several plant pathogenic fungi has been investigated.

(−)-Magnofargesin and (+)-magnoliadiol, two lignans from Magnolia fargesii

Abstract Two new lignans, (−)-magnofargesin and (+)-magnoliadiol, were isolated from the flower buds of Magnolia fargesii . The absolute configuration assignment of (−)-magnofargesin was achieved by its isomerization to (+)-magnolin.