Takakazu Shinzato

Stereochemistry of megastigmane glucosides from Glochidion zeylanicum and Alangium premnifolium.

From Glochidion zeylanicum, two megastigmane glucosides, 3- and 9-O-beta-D-glucopyranosides of (3S,5R,6R,7E,9S)-megastigman-7-ene-3,5,6,9-tetrol (1 and 2, respectively), were isolated. Their structures were different from those of kiwiionoside (3) and actinidioionoside (4), isolated from Actinidia chinensis and Actinidia polygama, respectively, in the stereochemistry at the 9-positions. Alangionosides E (5) and O (6), isolated from the leaves of Alangium premnifolium, are also megastigmane glucosides, and the latter is closely related to 1 and actinidioionoside (4). However, the absolute configurations of the 9-position remained to be determined. They were analyzed to be R by means of a modified Moshers method. Alangionoside E (5) is identical with corchoionoside A in all aspects. The name of corchoionoside A must be retained thereafter.

Euodionosides A-G: megastigmane glucosides from leaves of Euodia meliaefolia.

From a 1-BuOH-soluble fraction of the MeOH extract of leaves of Euodia meliaefolia, collected in Okinawa, seven megastigmane glucosides, named euodionosides A-G, were isolated together with three known megastgmane glucosides, and two aliphatic and three phenolic compounds. Their structures were elucidated through a combination of spectroscopic analyses and application of the modified Moshers method.

Macaflavanones A-G, Prenylated Flavanones from the Leaves of Macaranga tanarius

Phytochemical investigation of leaves of Macaranga tanarius resulted in the isolation of seven new prenylated flavanones, macaflavanones A-G (1-7), along with two known compounds, nymphaeol C (9) and the diterpene kolavenol. The structures of the new compounds were elucidated by means of a combination of spectroscopic methods and chemical conversion. The absolute structure of tanariflavanone B (8), isolated from the title plant, was also resolved. The cytotoxic activities of isolated flavanones were assayed using two cell lines, with macaflavanone G (7) being the most active compound in each case.

Chlorine-containing iridoid and iridoid glucoside, and other glucosides from leaves of Myoporum bontioides

Sixteen compounds were isolated from the MeOH extract of leaves of Myoporum bontioides. The five compounds hitherto unknown, were elucidated to be a chlorine-containing iridoid, named myopochlorin, and an iridoid glucoside, an acylated iridoid glucoside, a linear acetogenin glucoside, and an acyclic monoterpene glucoside, named myobontiosides A-D, respectively, by means of spectroscopic analyses.

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.

Sprouting characteristics of a subtropical evergreen broad-leaved forest following clear-cutting in Okinawa, Japan

This study explores the sprouting characteristics of an evergreen broad-leaved forest after clear-cutting based on a survey of 1,893 stumps of 62 tree species in Okinawa, Japan. The sprouting capabilities of the stumps varied among tree species. The stumps of 60 species could produce sprouts, while those of the other two species could not. In 10 of the sprouting species, the mean sprout-stem number was higher than 4.0 stems per stump; nine sprouting species showed low sprouting capabilities. Additionally, Castanopsis sieboldii and Schima wallichii, the dominant species, exhibited high sprouting capabilities. Further, the sprouting capabilities varied with stump diameter at breast height (DBH). Stumps with a larger DBH tended to have a higher mean number of sprout stems per stump, higher DBH, and higher tree height than the smaller stumps. The forest stands regenerated by sprouting might recover into a tree community similar to that before clear-cutting.

Glycosidic constituents of the leaves of an Okinawan Leguminosae plant, Derris trifoliata Lour.

From the leaves of Derris trifoliata, collected in Okinawa, 15 glycosidic compounds were isolated and identified.