Chemical constituents from the peels of Citrus sudachi.

A methanol extract of the peels of Citrus sudachi gave five new compounds (1-5) and 27 known compounds. The structures were elucidated on the basis of spectroscopic evidence. Several of these compounds were assayed for antimicrobial activity against methicillin-resistant Staphylococcus aureus and Helicobacter pylori, and sudachitin (6) and 3'-demethoxysudachitin (7) were the most active.

Antibacterial and antioxidant activities of quercetin oxidation products from yellow onion (Allium cepa) skin.

Four new quercetin-derived oxidation products (1-4) and lunularin-4-O-beta-D-glucoside (5) were isolated from a water extract of onion (Allium cepa) skin, together with 17 other known compounds. Antibacterial assays for the isolated compounds showed that 2-(3,4-dihydroxyphenyl)-4,6-dihydroxy-2-methoxybenzofuran-3-one (1) presented selective activity against Helicobacter pylori strains and 3-(quercetin-8-yl)-2,3-epoxyflavanone (4) showed antibacterial activity against MRSA and H. pylori strains at the same time that it increased susceptibility of MRSA to beta-lactams. Evaluation of antioxidant activity against DPPH for the isolated compounds showed that the new derivative compounds (1-4) and 2,5,7,3',4'-pentahydroxy-3,4-flavandione (6) are more active than quercetin.

Anti-Helicobacter pylori compounds from Santalum album.

Six new sesquiterpenes, (Z)-2beta-hydroxy-14-hydro-beta-santalol (1), (Z)-2alpha-hydroxy-albumol (2), 2R-(Z)-campherene-2,13-diol (3), (Z)-campherene-2beta,13-diol (4), (Z)-7-hydroxynuciferol (5), and (Z)-1beta-hydroxy-2-hydrolanceol (6), together with five known compounds, (Z)-alpha-santalol (7), (Z)-beta-santalol (8), (Z)-lanceol (9), alpha-santaldiol (10), and beta-santaldiol (11), were isolated from Santalum album, by using bioassay-guided fractionation for Helicobacter pylori. The structures were determined by extensive NMR studies. The absolute configuration of compound 3 was determined by a modified Mosher method. The crude extracts as well as the isolated compounds showed antibacterial activity against H. pylori. Especially, compounds 7 and 8 have strong anti-H. pylori activities against a clarithromycin-resistant strain (TS281) as well as other strains.

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.

New stilbene derivatives from Calligonum leucocladum.

Two new stilbene derivatives, (E)-resveratrol 3-(6' '-galloyl)-O-beta-D-glucopyranoside (1) and (E)-resveratrol 3-(4' '-acetyl)-O-beta-D-xylopyranoside (2), and five known stilbene derivatives (3-7) were isolated from the dried aerial parts of Calligonum leucocladum. Their structures were established on the basis of spectroscopic evidence. Compound 1 showed antioxidant activity and a restorative effect of the inhibition of oxacillin to oxacillin/methicillin-resistant Staphylococcus aureus.

Sesquiterpenoids from Artemisia gilvescens and an anti-MRSA compound.

A new secoguaianolide sesquiterpene (1) was isolated along with its three stereoisomers (2-4) from the nonmedicinal plant Artemisia gilvescens. The structure of 1 was elucidated to be (4S,5S)-dihydro-5-[(1R,2S)-2-hydroxy-2-methyl-5-oxo-3-cyclopenten-1-yl]-3-methylene-4-(3-oxobutyl)-2(3H)-furanone on the basis of 2D NMR and other spectroscopic evidence. Five known sesquiterpenoids were also isolated from this plant, and one of them (5) showed activity against methicillin-resistant Staphylococcus aureus (MRSA).

Benzoylphloroglucinol derivatives from Hypericum scabrum.

Nine new polyprenylated benzoylphloroglucinol derivatives, hyperibones A-I (1-9), were isolated from the aerial parts of the Uzbekistan medicinal plant Hypericum scabrum. Their structures were determined mainly on the basis of spectroscopic evidence (2D NMR and HRMS). Compounds 1, 2, and 4 showed mild in vitro antibacterial activity against methicillin-resistance Staphylococus aureus (MRSA) and methicillin-sensitive Staphylococus aureus (MSSA).

Coumarins and gamma-pyrone derivatives from Prangos pabularia: antibacterial activity and inhibition of cytokine release.

The n-hexane and ethyl acetate extracts of the stems and the ethyl acetate extracts of roots from Prangos pabularia afforded an gamma-pyrone derivative and furanocoumarin derivatives with three glucose and gamma-pyrone (pabularin A, B and C), along with 26 previously known compounds (18 coumarins, six terpenoids and two glycosides). Their structures were established on the basis of spectroscopic studies. Of these, 16 coumarin derivatives isolated from P. pabularia were tested for antibacterial activity and inhibition of cytokine release.