Studies on curcumin and curcuminoids. XLVI. Photophysical properties of dimethoxycurcumin and bis-dehydroxycurcumin.

The steady-state absorption and fluorescence, as well as the time-resolved fluorescence properties of dimethoxycurcumin and bis-dehydroxycurcumin dissolved in several solvents differing in polarity and H-bonding capability are presented. The singlet oxygen generation efficiency of the two compounds relative to curcumin is estimated. The photodegradation quantum yield of the former compound in acetonitrile and methanol is determined. The dimethoxycurcumin and bis-dehydroxycurcumin decay mechanisms from the S (1) state are discussed and compared with those of curcumin, dicinnamoylmethane and bis-demethoxycurcumin.

A screening of curcumin derivatives for antibacterial phototoxic effects studies on curcumin and curcuminoids. XLIII.

Curcumin, bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, has potential as a photosensitiser for photodynamic treatment of localised superficial infections in e.g., the mouth or skin. The aim of the present study was to evaluate the in vitro antibacterial phototoxic potential of a series of five curcumin derivatives. The gram-positive Enterococcus faecalis and the gram-negative Escherichia coli were used as bacterial models. The bacteria were exposed to curcuminoid preparations in two concentrations (2.5 and 25.0 microM) in combination with a constant irradiation dose (5 J/cm2). The UV-VIS absorption spectrum of the curcuminoids was in the same range as curcumin, 300-500 nm. Compound 1 (dimethoxycurcumin; C1) and compound 3 (bisdemethoxycurcumin; C3) were strongly phototoxic towards E. faecalis (no surviving bacteria) and showed a lower but significant effect towards E. coli (< or = 0.5 log reductions and 1 - 4 log reductions, respectively). Compound 2 (C2) and compound 4 (C4) in combination with blue light reduced the colony forming ability of E. faecalis (approximately 1-4 log reductions). The phototoxic effect of the curcuminoids varied with concentration, and for compounds C1, C2 and C3 it was further influenced by the addition of polyethylene glycol 400 (PEG 400) to the preparations. 2,6-Divanillylidenecyclohexanone (C5) showed very low phototoxic potential (< 0.2 log reductions) under the conditions used in the present study. The addition of polyethylene glycol 400 (PEG 400) seemed to increase the solubility of compound C1, C3 and C5 in phosphate buffered saline (PBS). This investigation demonstrates the importance and influence of the substituents on the phenolic rings and the keto-enol moiety for the phototoxic potential of curcumin and its derivatives.

Photokilling of bacteria by curcumin in selected polyethylene glycol 400 (PEG 400) preparations. Studies on curcumin and curcuminoids, XLI.

Curcumin, bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, is a yellow-orange pigment which can be synthesised chemically or isolated from the plant Curcuma longa L. Curcumin has a rather broad absorption peak in the range 300-500 nm (maximum approximately 430 nm) and has potential as a photosensitiser for treatment of localised superficial infections in e.g., the mouth or skin. Previously, we have demonstrated phototoxic effects of curcumin in selected aqueous preparations against both gram-positive Enterococcus faecalis and Streptococcus intermedius and gram-negative Escherichia coil bacteria in vitro. One of the most efficient preparations was curcumin in polyethylene glycol (PEG 400) dissolved in phosphate buffered saline (PBS), pH 6.1. In this study the solubilising effect of PEG 400 on curcumin molecules and the in vitro phototoxic effects of these preparations were further evaluated. The effect of varying the curcumin concentration (2.50 microM -25.00 microM), the radiant exposure (0.5-30 J/cm2) and the physical state of curcumin against the survival of E. coli was investigated. PEG 400 showed an increasing physically stabilising effect towards crystallisation of curcumin in aqueous preparation with increasing concentrations (2.5%-10.0% v/v). Despite a higher solubility of curcumin with increasing PEG 400 concentrations, the surfactant reduced the phototoxicity of curcumin against E. coil. The highest phototoxic effect was obtained when curcumin was present in the least physically stable preparation, a stock solution in ethanol added to PBS with or without the lowest test concentration of PEG 400 (2.5% v/v). The obtained phototoxic effect can be increased by increasing the irradiation dose or by choosing an optimal curcumin concentration. E. faecalis was efficiently killed by the lowest concentration of curcumin in combination with the lowest radiant exposure when curcumin was dissolved in certain PEG solutions (< 0.02% survival), but showed no reduction when exposed to preirradiated curcumin.

Photokilling of bacteria by curcumin in different aqueous preparations. Studies on curcumin and curcuminoids XXXVII.

Curcumin has potential as a photosensitiser (PS) in photodynamic therapy (PDT) for localised superficial infections. However, it is a challenge to make an optimal curcumin formulation in which curcumin has acceptable solubility and stability at physiological pH and combined with high selective phototoxic activity towards bacteria. In the present study, the phototoxic effects of curcumin against gram-negative and gram-positive bacteria were investigated in selected aqueous preparations. The gram-positive Enterococcus faecalis and Streptococcus intermedius and the gram-negative Escherichia coli were used as bacterial models. The bacteria were exposed to 1-25 microM curcumin solubilised in DMSO, cyclodextrines, liposomes and surfactants known to interfere with membranes. After 30 min incubation the bacteria were irradiated with fluorescent tubes emitting blue light (emission max 430 nm). The irradiance was 17 mW/cm2 and the radiant exposure (light dose) was 0.5-30J/cm2. The bacterial survival was calculated as a percentage compared to controls. Various post-irradiation incubation times were tested. Curcumin's native fluorescence was exploited in examination of curcumin uptake in or adherence to bacteria by fluorescence microscopy. Changes in post-irradiation incubation time, curcumin concentration, irradiation dose and preparation strongly influenced the phototoxic efficiency of curcumin in vitro. Aqueous preparations of DMSO, polyethyleneglycol and the pluronic block copolymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) were the most efficient vehicles for curcumin to exert photokilling of gram-positive and gram-negative bacteria.

Subacute and acute epidemic conjunctivitis due to neisseria gonorrhoeae SSP

An outbreak of acute conjunctivitis with profuse exudation was observed between November 1987 and June 1988 in Konso; North Omo. There were 9;075 registered cases and seven months later; 20 cases with mild; subacute conjunctivitis were observed. Neisseria gonorrhoeae and Neisseria gonorrhoeae subsp. kochii were the causative agents; while Haemophilus spp. behaved as opportunistic infection. The condition is resistant to topical antibiotics; but the outbreak could be controlled by mass treatment with single dose oral ampicillin and probenecid. Severe sequelae were observed in 36 patients treated with this regimen. This is the first isolation of N. gonorrhoeae subsp. kochii outside Egypt; and the first recorded outbreak of Neisseria gonorrhoeae conjunctivitis affecting thousands of patients in more than 40 years