[Antioxidant and antibacterial activities of dimeric phenol compounds].

We studied the antioxidant and antibacterial activities of monomeric and dimeric phenol compounds. Dimeric compounds had higher antioxidant activities than monomeric compounds. Electron spin resonance spin-trapping experiments showed that phenol compounds with an allyl substituent on their aromatic rings directly scavenged superoxide, and that only eugenol trapped hydroxyl radicals. We developed a generation system of the hydroxyl radical without using any metals by adding L-DOPA and DMPO to PBS or MiliQ water in vitro. We found that eugenol trapped hydroxyl radicals directly and is metabolized to a dimer. On the other hand, dipropofol, a dimer of propofol, has strong antibacterial activity against Gram-positive bacteria. However, it lacks solubility in water and this property is assumed to limit its efficacy. We tried to improve the solubility and found a new solubilization method of dipropofol in water with the addition of a monosaccharide or ascorbic acid.

A novel indole-diterpenoid, JBIR-03 with anti-MRSA activity from Dichotomomyces cejpii var. cejpii NBRC 103559.

A new indole-diterpene, JBIR-03 (1), was isolated from the fungus Dichotomomyces cejpii var. cejpii NBRC 103559 and its structure was determined based on the spectroscopic data. 1 exhibited anti-MRSA (methicillin-resistant Staphylococcus aureus) activity and antifungal activity against apple Valsa canker-causing fungus, Valsa ceratosperma, while it exhibited no toxicity towards human cancer cells.

DMPO-OH radical formation from 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in hot water.

When an aqueous solution of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was heated at 70 degrees C for 30 min, formation of DMPO-OH was observed by ESR. This DMPO-OH radical formation was suppressed under an argon atmosphere. When water was replaced with ultra-pure water for ICP-MS experiments, DMPO-OH radical formation was also diminished. Under an argon atmosphere in ultra-pure water, the intensity of the DMPO-OH signal decreased to about 1/20 of that observed under aerobic conditions with regular purified water. The addition of hydroxyl radical scavengers such as mannitol did not affect the formation of DMPO-OH, but the signal turned faint in the presence of EDTA. We suggest that DMPO reacted with dissolved oxygen to form DMPO-OH.

The critical threshold of 3-nitropropionic acid-induced ischemic tolerance in the rat.

3-Nitropropionic acid (3-NPA) is a suicide inactivator of succinate dehydrogenase (SDH), commonly used as a pharmacological model of Huntington's disease in rodents. Several studies have shown that a single administration of 3-NPA given systemically provides subsequent ischemic tolerance. The present study has tested the hypothesis that 3-NPA is capable of inducing tolerance in a model of permanent focal cerebral ischemia and whether 3-NPA can be truly applicable as a tolerance-inducer to ischemia. Rats given 3-NPA intraperitoneally revealed that the mortality of 3-NPA of 15, 20, and 25 mg/kg groups was 20.5, 38.8, and 83.3%, respectively. All rats survived without behavioral sequelae at smaller doses. Three days after 3-NPA preconditioning, the rats showing no behavioral changes underwent the permanent middle cerebral artery occlusion. The groups treated with 10 and 15 mg/kg of 3-NPA showed significantly reduced neurological deficits and infarction volumes in comparison with the control group, whereas the groups treated with 5 and 20 mg/kg of 3-NPA revealed no tolerance effects. When the regional SDH activity (% of control) was photometrically semi-quantified, it was observed that the activity was reduced to 90.8, 76.1, 67.8, and 64.3% in the outer layers of the cerebral cortex, and to 79.4, 67.5, 63.2, and 62.9% in the striatum 1 h after 3-NPA application (5, 10, 15, 20 mg/kg), respectively. In conclusion, although the preconditioning with 3-NPA is clearly shown in the setting of permanent ischemia, the preconditioning with this mitochondrial toxin demonstrated a rather narrow safety margin (critical threshold).

Inhibitory effect of Lysichiton camtschatcense extracts on Fe2+/ascorbate-induced lipid peroxidation in rat kidney and brain homogenates.

Lysichiton camtschatcense is a well-known plant in Japan where it has been used as a traditional medicine by the "Ainu" people for the treatment of acute nephritis. It is presumed that L. camtschatcense has an inhibitory effect against nephritis caused by reactive oxygen species (ROS) owing to its antioxidant activities. Consequently, the antioxidant effect of L. camtschatcense extracts was assessed against Fe(2+)/ascorbic acid (AsA)-induced lipid peroxidation in rat kidney and brain homogenates. The antioxidant effect of the chloroform extract (CE) was more potent than that of the methanol extract (ME) for both homogenates. The antioxidant effect of both extracts was similar to those of alpha-tocopherol, a lipid-soluble antioxidant, and glutathione (GSH), a water-soluble antioxidant, which were used as reference compounds. Although CE showed a low radical-scavenging effect for superoxide anion radicals (O(2)(*-)) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, assessed by using an electron spin resonance (ESR) method, hydroxyl radicals (*OH) were markedly scavenged by more than 80%. On the other hand, ME showed more significant scavenging effect for DPPH radicals and O(2)(*-) than CE. These results suggest that the inhibitory effects of the L. camtschatcense extract on lipid peroxidation in rat kidney and brain are based on its high radical-scavenging effect against *OH, O(2)(*-) , and lipid-derived radicals generated from the cell membrane.

Solubilization of dipropofol, an antibacterial agent, using saccharide and ascorbic acid.

Dipropofol has a strong antibacterial activity against Gram-positive bacteria. However, it lacked the solubility in water and this property was supposed to limit its efficacy. We tried to improve the solubility and found a new solubilization method of dipropofol in water by the addition of a monosaccharide or ascorbic acid.

Antioxidant activity of propofol and related monomeric and dimeric compounds.

This study was carried out to investigate the antioxidant activity of propofol (2,6-diisopropylphenol) and its related compounds, butylated hydroxyanisole (BHA), 2,6-dimethylphenol, 2,6-di-t-butylphenol, and their dimeric compounds. The degree of antioxidant activity was evaluated based on the degree of peroxidation induced with Fe-ascorbic acid in egg phosphatidylcholine through the determination of thiobarbituric acid-reactive substances (TBARS) formed during peroxidation. Their antioxidant activities were in the order of dipropofol>di(2,6-di-t-butylphenol)>diBHA>di(2,6-dimethylphenol). Dipropofol, a dimeric compound of propofol, showed the highest antioxidant activities. Dimeric compounds had higher activities than monomeric compounds, and the 1,1-diphenyl-p-picryhydrazyl-trapping ability of dimeric compounds was also greater than those of monomeric compounds (4-10-fold). These results suggest that dimeric phenols may increase their antioxidant activities along with increments in the conjugation system and play a inhibitory role in the propagation of free radical chain reactions.

Acetylated aporphine alkaloids from Lysichiton camtschatcense.

Two N,O-diacetylaporphine alkaloids, N,O-diacetylnoroliveroline (1) and N,O-diacetyl-(-)-nornuciferidine (2), have been isolated and characterized from the rhizomes of Lysichiton camtschatcense. Their structures were determined by spectroscopic data analysis. DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals were scavenged by compounds 1 and 2, but with weak activity.

Mechanism of action of dipropofol and synergistic action with other antibacterial agents in vitro.

The mode of action of dipropofol and its antibacterial activity in combination with other antibiotics against Gram-positive and -negative bacteria were investigated. Dipropofol showed a bactericidal effect against Staphylococcus aureus 209P, and inhibited the incorporations of 3H-glutamate and 3H-leucine into S. aureus 209P and Bacillus subtilis PCI219 cells. These results indicated that the mechanism of action of dipropofol was mediated by the inhibition of protein synthesis or amino acid incorporation. A synergistic effect was performed by checkerboard titration with Muller-Hinton agar plates containing dipropofol (0.39 microg/ml, 1/4 x MIC) and various concentrations of nine other antibiotics in vitro. The synergism against vancomycin resistant Enterococcus faecium was confirmed in the combination of dipropofol with rifampicin. The MIC of rifampicin was decreased from 0.39 microg/ml to <0.005 microg/ml by the addition of dipropofol. This combinational effect in reversing vancomycin resistance of enterococci highlights novel drug targets and has importance in the design of new therapeutic regimens against resistant pathogens.

Antibacterial activity of dipropofol and related compounds.

Phenolic compounds, in general, exhibit antioxidant and antibacterial activities. We studied antimicrobial activity of the phenolic antioxidants, propofol (2,6-diisopropylphenol), tocopherol, eugenol, butylated hydroxyanisole (BHA), and several of their dimer compounds. Dipropofol (dimer of 2,6-diisopropylphenol) showed strong antibacterial activity against gram-positive strains including methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococci (VRE), while propofol and other monomeric and dimeric phenols having methyl or tert-butyl groups showed no remarkable activity. The results indicated that the dimeric structure of 2,6-diisopropylphenol moiety may play an important role in the antibacterial activity.

Trapping effect of eugenol on hydroxyl radicals induced by L-DOPA in vitro.

Many researchers have stated that eugenol might inhibit lipid peroxidation at the stage of initiation, propagation, or both, and many attempts have been made to elucidate the mechanism of its antioxidant activity. Nevertheless, details of its mechanism are still obscure. This study was carried out to investigate the trapping effect of eugenol on hydroxyl radical generated from L-3,4-dihydroxyphenylalanine (DOPA) in MiliQ water and the generation mechanism of the hydroxyl radical by this system which uses no metallic factor. This was studied by adding L-DOPA and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) to phosphate buffered saline (PBS) or MiliQ water, and the generation of hydroxyl radical was detected on an ESR spectrum. By this method, the effect of antioxidants was detected as a modification of ESR spectra. We found that the eugenol trapped hydroxyl radicals directly, because it had no iron chelating action, did not trap L-DOPA semiquinone radical and inhibited hydroxyl radicals with or without iron ion.