Rigenolides D-H, norsecoiridoid and secoiridoids from Gentiana rigescens Franch.

Five new compounds, rigenolides D-H (1-5), were isolated from the aerial parts of Gentiana rigescens Franch. Their structures were assigned by detailed spectroscopic analyses and chemical conversions. Rigenolides D (1) and E (2) were elucidated to be a secoiridoid and a norsecoiridoid, respectively, possessing a dienone moiety in common. Rigenolides F-H (3-5) were assigned as acylated secoiridoid glucosides.

Tetrahydroxanthones from Mongolian medicinal plant Gentianella amarella ssp. acuta.

Two tetrahydroxanthones, 1,3,5S,8S-tetrahydroxy-5,6,7,8-tetrahydroxanthone (1) and 1,3,5R,8S-tetrahydroxy-5,6,7,8-tetrahydroxanthone (2), and six new tetrahydroxanthone glycosides, amarellins A-F (3-8), were isolated from the aerial parts of a Mongolian medicinal plant Gentianella amarella ssp. acuta (Gentianaceae). The structures of 1-8 were elucidated on the basis of spectroscopic analysis, chemical conversion, and ECD calculation. Amarellins A-C (3-5) were assigned as 8-O-ß-D-glucoside, 8-O-ß-D-xyloside, and 1-O-ß-D-glucoside of 1, respectively, while amarellins D-F (6-8) were elucidated to be 8-O-ß-D-xyloside, 1-O-ß-D-glucoside, and 3-O-ß-D-glucoside of 2, respectively.

Two new bicyclic sulfoxides from Welsh onion.

Newly identified bicyclic sulfoxides, welsonins A1 (1) and A2 (2), were isolated from acetone extracts of the bulbs of the Welsh onion (Allium fistulosum). In this study, the structures of 1 and 2, which are tetrahydrothiophene-S-oxide derivatives, were characterized by spectroscopic analysis. These compounds appeared to be derived from the coupling of 1-propenyl sulfenic acid and uronic acid. Welsonin A1 (1) showed the potential to suppress tumor-cell proliferation by inhibiting the polarization of alternatively activated M2 macrophages.

Isolation and characterization of new onionins A2 and A3 from Allium cepa, and of onionins A1, A2, and A3 from Allium fistulosum.

In this study, the new stable sulfur-containing compounds onionins A2 (1) and A3 (2) were isolated from the acetone extracts of the bulbs of Allium cepa L. and identified as the stereoisomers of onionin A1 discovered in our previous study. Their chemical structures, 3,4-dimethyl-5-(1E-propenyl)-tetrahydrothiophene-2-sulfenic acid-S-oxides, were characterized using various spectroscopic techniques. In addition, 1 and 2 together with onionin A1 were successfully isolated from the leaves of the Welsh onion, Allium fistulosum L. The onion-extracted fractions showed good potential to inhibit the polarization of M2 activated macrophages, indicating their possible ability to inhibit tumor cell proliferation.

Hypelodins A and B, polyprenylated benzophenones from Hypericum elodeoides.

Two new polyprenylated benzophenones, hypelodins A (1) and B (2), were isolated from the aerial parts of the Chinese medicinal plant Hyperium elodeoides (Choisy). Their structures were elucidated on the basis of spectroscopic evidence. Hypelodin A (1) is a polyprenylated benzophenone having a tetrahydropyrane ring with three prenyl groups and one 4-methyl-1,3-pentadiene moiety, while hypelodin B (2) has a cage-like structure with a 6/6/5/7/6/5 hexacyclic ring system.

Acyclic sulfides, garlicnins L-1-L-4, E, and F, from Allium sativum.

Six novel acyclic sulfides, named garlicnins L-1-L-4 (1-4), E (5), and F (6), were isolated from the acetone extracts, with the ability to suppress M2 macrophage activation, of the bulbs of garlic (Allium sativum L.), and their chemical structures were characterized.

Rigenolide A, a new secoiridoid glucoside with a cyclobutane skeleton, and three new acylated secoiridoid glucosides from Gentiana rigescens Franch.

Rigenolide A (1), a new secoiridoid glucoside with a cyclobutane skeleton and three new acylated secoiridoid glucosides, 2'-(2,3-dihydroxybenzoyl)-gentiopicroside (2), 2'-(2,3-dihydroxybenzoyl)-swertiamarin (3), 3'-(2,3-dihydroxybenzoyl)-sweroside (4), along with two noriridoids (7 and 8) and two known secoiridoid glucosides (5 and 6), were isolated from Gentiana rigescens Franch. The structures of new compounds were elucidated by extensive spectroscopic analyses. The isolated compounds were evaluated for DPPH free-radical scavenging activity.

New spirostanol glycosides from Solanum nigrum and S. jasminoides.

A new characteristic steroidal glycoside possessing a hydroxyl group at C-23, inunigroside A (1), was isolated from the withered berries of Solanum nigrum L. On the basis of spectroscopic analysis, the structure of 1 was characterized as (5α,22S,23S,25R)-3ß,23-dihydroxyspirostane 3-O-ß-lycotetraoside. Next, a major steroidal sapogenol, (22R, 25S)-3ß,15α-dihydroxy-spirost-5-ene (3), was obtained from the acid hydrolysate of the methanolic extract of the aerial parts of Solanum jasminoides L. A new bisdesmoside, 3-O-ß-D-glucopyranosyl-(1→4)-ß-D-glucopyranosyl-(1→4)-ß-D-glucopyranosyl (22R,25S)-3ß,15α-dihydroxyspirost-5-ene 15-O-α-L-rhamnopyranoside (4), named jasminoside A, was isolated from the methanolic extract of S. jasminoides.

Spicachlorantins G-J, new lindenane sesquiterpenoid dimers from the roots of Chloranthus spicatus.

Four new lindenane sesquiterpenoid dimers, spicachlorantins G-J (1-4), were isolated from the roots of Chloranthus spicatus together with seven known compounds, including chloramultilide A, shizukaol B, shizukaol D, shizukaol F, shizukaol P, chlorahololide D, and cycloshizukaol A. The planar structures of the new compounds were established by 1D-, 2D-NMR, and MS analyses. The absolute configurations of these compounds were determined by analyzing rotating Overhauser enhancement and exchange spectroscopy (ROESY) and circular dichroism (CD) spectra.

Study of constituents of Veronicastrum villosulum.

We investigated the constituents of Veronicastrum villosulum (Miquel) Yamazaki (Scrophulariaceae), an endangered species belonging to the IA group. From the aerial parts of this plant cultivated at the botanical garden of Sojo University, we isolated two new cucurbitacine-type glycosides, 3-O-alpha-L-rhamnopyranosyl-(1 --> 2)-[beta-D-glucopyranosyl-(1 --> 3)]-beta-D-glucopyranosides of 3beta,25-dihydroxycucurbit-5,23(E)-diene-7-one-25-methyl ether and 3beta,23-dihydroxycucurbit-5,24-diene-7-one-23-methyl ether.

A new spirostanol glycoside from fruits of Solanum indicum L.

A new characteristic steroidal glycoside of the 23S,26R-hydroxylated spirostanol-type named indioside F was isolated from the fruit of Solanum indicum, along with indioside A and protodioscin. On the basis of spectroscopic analysis, the structure of indioside F was found to be 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranosyl (beta-chacotriosyl) (22R,23S,25R,26R)-spirost-5-ene-3beta,23,26-triol.

Alkyl gallates, intensifiers of beta-lactam susceptibility in methicillin-resistant Staphylococcus aureus.

We found that ethyl gallate purified from a dried pod of tara (Caesalpinia spinosa) intensified beta-lactam susceptibility in methicillin-resistant and methicillin-sensitive strains of Staphylococcus aureus (MRSA and MSSA strains, respectively). This compound and several known alkyl gallates were tested with MRSA and MSSA strains to gain new insights into their structural functions in relation to antimicrobial and beta-lactam susceptibility-intensifying activities. The maximum activity of alkyl gallates against MRSA and MSSA strains occurred at 1-nonyl and 1-decyl gallate, with an MIC at which 90% of the isolates tested were inhibited of 15.6 microg/ml. At concentrations lower than the MIC, alkyl gallates synergistically elevated the susceptibility of MRSA and MSSA strains to beta-lactam antibiotics. Such a synergistic activity of the alkyl gallates appears to be specific for beta-lactam antibiotics, because no significant changes were observed in the MICs of other classes of antibiotics examined in this study. The length of the alkyl chain was also associated with the modifying activity of the alkyl gallates, and the optimum length was C5 to C6. The present work clearly demonstrates that the length of the alkyl chain has a key role in the elevation of susceptibility to beta-lactam antibiotics.