Yoshio Takeda

Megastigmane glucosides and an unusual monoterpene from the leaves of Cananga odorata var. odorata, and absolute structures of megastigmane glucosides isolated from C. odorata var. odorata and Breynia officinalis

From a 1-BuOH-soluble fraction of a MeOH extract of Canangaodorata var. odorata, collected at the Botanical Garden of Chiang Mai University, a new megastigmane glucoside, named canangaionoside, and an irregular monoterpene were isolated. A known compound, breyniaionoside A, which has been obtained from the leaves of Breyniaofficinalis, was also isolated, and its absolute structure was substantiated for the first time in this study. On this occasion, the absolute stereochemistries of structurally related megastigmane glucosides, breyniaionosides B and C, isolated from B.officinalis were examined.

A glycerol α- d -glucuronide and a megastigmane glycoside from the leaves of Guettarda speciosa L.

From the 1-BuOH-soluble fraction of a MeOH extract of the leaves of Guettarda speciosa L., two new compounds (1, 2) were isolated together with six known compounds. Spectroscopic analysis of 1 and 2 established their structures to be derivatives of a glycerol α-glucuronide and a megastigmane glycoside, respectively. HPLC analysis of the hydrolyzate of 1 confirmed the presence of d-glucuronic acid in the structure, and the modified Mosher’s method established the absolute structure of 2.

Secoiridoid and iridoid glucosides from the leaves of Fraxinus griffithii

Phytochemical investigation of the dried leaves of Fraxinus griffithii collected in Okinawa has led to the isolation of three new secoiridoid glucosides, griffithosides A–C (1–3), and one new iridoid glucoside, 7-epi-7-O-(E)-caffeoylloganic acid (4), along with eight known secoiridoid glucosides (5–12). The structures of these compounds were elucidated by means of NMR, MS, and other spectroscopic techniques, as well as comparison with literature data. The isolated compounds were tested for radical-scavenging activity. Among them, compounds 3, 4, and 7 exhibited substantial radical-scavenging activity.

Microtropiosides A-F : ent-Labdane diterpenoid glucosides from the leaves of Microtropis japonica (Celastraceae)

From a 1-BuOH-soluble fraction of a MeOH extract of the leaves of Microtropis japonica, collected in the Okinawa islands, six ent-labdane glucosides, named microtropiosides A-F, were isolated together with one known acyclic sesquiterpene glucoside. Their structures were elucidated by a combination of spectroscopic analyses, and their absolute configurations determined by application of the beta-D-glucopyranosylation-induced shift-trend rule in (13)C NMR spectroscopy and the modified Moshers method.

Lignan and neolignan glucosides, and tachioside 2′- O -4″- O -methylgallate from the leaves of Glochidion rubrum

Thirteen compounds (1–13) were isolated from a MeOH extract of leaves of Glochidion rubrum. The structures of four new compounds were elucidated to be (−)-isolariciresinol 2a-O-β-d-glucopyranoside (1), (7R,8S)- and (7R,8R)-4,7,9,9′-tetrahydroxy-3,3′-dimethoxy-8-O-4′-neolignan 7-O-β-d-glucopyranosides (2 and 3, respectively), and tachioside 2′-O-4″-O-methylgallate (4) on detailed inspection of one- and two-dimensional NMR spectral data.

Crotonionosides A-G: megastigmane glycosides from leaves of Croton cascarilloides Räuschel.

From the 1-BuOH-soluble fraction of a MeOH extract of leaves of Croton cascarilloides, collected in Okinawa, Japan, seven megastigmane glycosides, named crotonionosides A-G, were isolated together with three known megastigmane glucosides, dendranthemosides A and B, and citroside A. This structures were elucidated by a combination of spectroscopic analyses, HPLC analyses, and application of the modified Moshers method.

Microtropins A–I: 6′-O-(2″S,3″R)-2″-Ethyl-2″,3″-dihydroxybutyrates of aliphatic alcohol β-d-glucopyranosides from the branches of Microtropis japonica

From the branches of Microtropis japonica (Celastraceae), nine aliphatic glucosides, named microtropins A-I, were isolated. The 6-position of glucose was esterified with (2S,3R)-2-ethyl-2,3-dihydroxybutyric acid. Microtropins A-D contained a rare natured product nitrile functional group in their aglycones. The absolute structures of the (2S,3R)-2-ethyl-2,3-dihydroxybutyric acid moiety and aglycone of microtropin A were determined by an X-ray crystallographic method.

Flavonol glycosides from the leaves of Indigofera zollingeriana

Two new flavonol glycosides were isolated from the 1-butanol (1-BuOH)-soluble fraction of a methanol (MeOH) extract of the leaves of Indigoferazollingeriana, along with four flavonol glycosides and three known megastigmane glucosides. The structures of the new compounds were elucidated by spectroscopic analyses as kaempferol 3-O-β-d-(2″-O-β-d-apiofuranosyl)glucopyranoside 7-O-α-l-rhamnopyranoside and 3-O-β-d-(2″-O-β-d-apiofuranosyl, 6″-O-α-l-rhamnopyranosyl)glucopyranoside 7-O-α-l-rhamnopyranoside.

Crotocascarins I-K: Crotofolane-Type Diterpenoids, Crotocascarin γ, Isocrotofolane Glucoside and Phenolic Glycoside from the Leaves of Croton cascarilloides.

From the 1-BuOH-soluble fraction of a methanol (MeOH) extract of the leaves of Croton cascarilloides, crotofolanes: crotocascarins I-K, nor-crotofolane: crotocascarin γ, isocrotofolane glucoside and phenolic glycoside were isolated by a combination of various separation techniques. Their structures were elucidated mainly from the NMR spectroscopic evidence. The structure of crotocascarin K was first elucidated by spectroscopic analysis and then was confirmed by X-ray crystallographic analysis. Its absolute structure was finally determined by the modified Moshers method. Isocrotofolane glucoside was found to possess a new skeleton, however, its absolute structure remains to be determined.

Prenylated flavonoid glucoside and two aliphatic alcohol glycosides from the leaves of Euodia meliaefolia (Hance) Benth

A new prenylated flavonoid (1) and two new aliphatic glycosides (2, 3) have been isolated from leaves of Euodia meliaefolia (Hance) Benth., together with three known compounds, (2R,3R)-5,7,4′-trihydroxy-8-(3-methylbut-2-enyl)dihydroflavonol 7-O-β-d-glucopyranoside (phellamurin) (4), (2R,3R)-dihydroquercetin 3′-O-β-d-glucopyranoside (5), and (7R,8S)-dihydrodiconiferyl alcohol 4-O-β-d-glucopyranoside (6). Their structures were determined on the basis of the results of spectroscopic analysis.