Re-evaluation of erythritol (E 968) as a food additive

This opinion addresses the re-evaluation of erythritol (E 968) as food additive and an application for its exemption from the laxative warning label requirement as established under Regulation (EU) No 1169/2011. Erythritol is a polyol obtained by fermentation with Moniliella pollinis BC or Moniliella megachiliensis KW3-6, followed by purifications and drying. Erythritol is readily and dose-dependently absorbed in humans and can be metabolised to erythronate to a small extent. Erythritol is then excreted unchanged in the urine. It does not raise concerns regarding genotoxicity. The dataset evaluated consisted of human interventional studies. The Panel considered that erythritol has the potential to cause diarrhoea in humans, which was considered adverse because its potential association with electrolyte and water imbalance. The lower bound of the range of no observed adverse effect levels (NOAELs) for diarrhoea of 0.5 g/kg body weight (bw) was identified as reference point. The Panel considered appropriate to set a numerical acceptable daily intake (ADI) at the level of the reference point. An ADI of 0.5 g/kg bw per day was considered by the Panel to be protective for the immediate laxative effect as well as potential chronic effects, secondary to diarrhoea. The highest mean and 95th percentile chronic exposure was in children (742 mg/kg bw per day) and adolescents (1532 mg/kg bw per day). Acute exposure was maximally 3531 mg/kg bw per meal for children at the 99th percentile. Overall, the Panel considered both dietary exposure assessments an overestimation. The Panel concluded that the exposure estimates for both acute and chronic dietary exposure to erythritol (E 968) were above the ADI, indicating that individuals with high intake may be at risk of experiencing adverse effects after single and repeated exposure. Concerning the new application, the Panel concluded that the available data do not support the proposal for exemption.

Deterioration of direct restorative materials under erosive conditions with impact of abrasion and attrition in vitro

Objective

To compare the cumulative impact of sequential wear on mechanical properties and appearance of a composite resin (CR), Filtek Z250^®, a glass ionomer GI, Fuji IX GP^®, and a glass hybrid (GH), Equia Forte^®.

Material and Methods

Six equally sized specimens of each material were subjected to wear tests, i.e., simulation of brushing, chewing and acidic liquid exposure, mimicking at least 6 months of clinical exposure. Surface roughness, hardness, substance loss and degree of shade lightness were determined.

Results

Following wear tests, significant increase in surface roughness and decrease in hardness values were observed for all materials (p < .05). Significantly larger substance loss was found in Equia Forte^® specimens compared to Filtek Z250^® (p < .05), while that of Fuji IX^® exceeded the measurement capacity of the instrument. Opposite to the two other materials, the shade of Filtek Z250^® became darker.

Conclusions

Sequential wear exposure mimicking abrasion, erosion and attrition to products representing CR, GI and GH, caused weakening and change in appearance of the materials. The composite resin was the most mechanically resistant to the sequential wear.

Photoactive Zr-aromatic hybrid thin films made by molecular layer deposition

The principle of antimicrobial photodynamic therapy (PDT) is appealing because it can be controlled by an external light source and possibly the use of durable materials. However, to utilise such surfaces requires a process for their production that allows for coating on even complex geometries. We have therefore explored the ability of the emerging molecular layer deposition (MLD) technique to produce and tune PDT active materials. This study demonstrates how the type of aromatic ligand influences the optical and antimicrobial properties of photoactive Zr-organic hybrid thin films made by MLD. The three aromatic dicarboxylic acids: 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 2-amino-1,4-benzenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid have been combined with ZrCl₄ to produce hybrid coatings. The first system has not been previously described by MLD and is therefore more thoroughly investigated using in situ quartz crystal microbalance (QCM), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. The antibacterial phototoxic effects of Zr-organic hybrids have been explored in the Staphylococcus aureus bacteria model using a UVA/blue light source. Films based on the 2,6-naphthalenedicarboxylic acid linker significantly reduced the number of viable bacteria by 99.9%, while no apparent activity was observed for the two other photoactive systems. Our work thus provides evidence that the MLD technique is a suitable tool to produce high-quality novel materials for possible applications in antimicrobial PDT, however it requires a careful selection of aromatic ligands used to construct photoactive materials.

Photoactive organic–inorganic hybrid thin films for potential use in antimicrobial photodynamic therapy (PDT) were fabricated based on Zr clusters and three different aromatic dicarboxylic acid linkers using the molecular layer deposition (MLD) technique.

Re-evaluation of thaumatin (E 957) as food additive

The present opinion deals with the re-evaluation of thaumatin (E 957) when used as a food additive. Thaumatin is a natural plant protein, consisting of thaumatin I and thaumatin II proteins together with minor amounts of plant constituents, obtained by acidic aqueous extraction of the arils of the fruit of Thaumatococcus daniellii plant. The Panel followed the conceptual framework for the risk assessment of certain food additives and considered that thaumatin is a digestible protein; adequate exposure estimates were available; there was no concern with respect to the genotoxicity; no conclusion on oral allergenicity could be drawn from the available human data; no adverse effects were observed in sub-chronic toxicity studies in rats and dogs at the highest dose tested of up 5,200 and 1,476 mg/kg bodyweight (bw) per day, respectively, and in a prenatal developmental toxicity study up to 2,000 mg/kg bw per day; moderate confidence in the body of evidence supported the absence of association between exposure to thaumatin and adverse health outcomes. Therefore, the Panel concluded that there is no need for a numerical acceptable daily intake (ADI) for thaumatin (E 957) and, based on a margin of safety (MOS) of 5,417, considered to be an underestimate and derived using the highest 95th percentile (P95) exposure of 0.48 mg/kg bw per day in consumers only, there is no safety concern for thaumatin (E 957) at the regulatory maximum level exposure assessment scenario, which was considered the most appropriate. The Panel recommended that European Commission considers introducing in the EU specifications for thaumatin (E 957) a new specification limit for the minimum combined content of thaumatin I and II proteins in E 957, a specification limit for yeast, mould counts and Salmonella spp and lowering the existing maximum limit for arsenic along with the inclusion of maximum limits for mercury and cadmium.

In vitro abrasivity and chemical properties of charcoal-containing dentifrices

Objective

Charcoal-containing dentifrices are gaining popularity, but scientific information on their effect on oral health is scarce. This study investigated properties of dentifrices that may affect dentine abrasivity, as well as their ability to adsorb fluoride, their pH and the presence of harmful substances.

Materials and methods

The dentifrices NAO and COCO were subjected to the following analyses: abrasivity, expressed as mean abraded depth and relative dentin abrasivity (RDA), and surface roughness of extracted human molars (n = 30) after simulated brushing; fluoride adsorption measured as concentration change; pH measurements; detection of polycyclic aromatic hydrocarbons by gas chromatography–mass spectrometry. The products were compared to a reference dentifrice (Colgate^® MaxWhite), positive controls (ISO dentifrice slurry, activated charcoal for laboratory use) and a negative control (distilled water).

Results

The mean abraded depths of NAO and COCO were not different (p > .05), but higher than the reference dentifrice and the negative control (p < .05). The RDA values of NAO, COCO and the ISO dentifrice slurry were higher than the reference dentifrice value (p < .05) by up to 10 times. The dentine surface roughness was higher after brushing with NAO, COCO and ISO dentifrice slurry compared to distilled water (p < .05). No change in mean adsorbed fluoride concentration was observed after 24 h (p > .05). Both NAO and COCO were alkaline (pH > 7). Analysis of NAO revealed the presence of naphthalene (112.8 ± 2.0 ng/mL).

Conclusion

The charcoal-containing dentifrices were abrasive within acceptable limits set by ISO and did not adsorb fluoride. The presence of naphthalene in one product is a cause for concern.

Influence of formulation on photoinactivation of bacteria by lumichrome

Lumichrome, a photodegradation product of riboflavin, is an endogenous compound in humans. The compound is more photostable and a more efficient photogenerator of singlet oxygen than riboflavin. It absorbs radiation in the UVA and blue-light region, which can be an advantage in antibacterial photodynamic therapy (aPDT) of superficial infections. The aim of this study was to investigate the in vitro aPDT effect of various lumichrome pharmaceutical formulations. Solutions of lumichrome (10(-5) - 10(-3)M) were prepared in plain phosphate buffered saline (PBS) or in PBS solutions containing cyclodextrins, DMSO, PEG 400 or polyoxamers (Pluronic). Supersaturated solutions of lumichrome in PBS were prepared via the cosolvent and solvent evaporation method. Phototoxic effects of selected lumichrome preparations were studied in planktonic Gram-positive (E. faecalis) and Gram-negative (E. coli) bacteria models. The UVA/blue light source emitted mainly in the range 340-440 nm. Lumichrome was up to tenfold more phototoxic against Gram-positive than to Gram-negative bacteria. Bacterial eradication was induced after exposure of lumichrome formulations (PBS, PEG 400 and HPγCD) combined with 24J/cm2 UVA/blue light. Increasing the concentration of lumichrome did not enhance the phototoxic effect, probably due to radiation attenuation in the highly absorbing solution (inner filter effect). Cyclodextrins were efficient enhancers of the lumichrome solubility in aqueous solutions, but inhibited the phototoxic effect. The study demonstrates that assuming the use of an optimized formulation, lumichrome has potential as a UVA/blue light photosensitizer in aPDT.

Antibacterial phototoxic effects of synthetic asymmetric and glycosylated curcuminoids in aqueous formulations: studies on curcumin and curcuminoids. LIV

The aim of this study was to evaluate the in vitro phototoxic potential of synthetic asymmetric and glycosylated curcuminoids on planktonic model bacteria by counting the colony forming units. The Gram-positive Enterococcus faecalis and the Gram-negative Escherichia coli were exposed to aqueous solutions of the curcuminoids (⩽2.5 μM) in the presence or absence of selected pharmaceutical excipients (Pluronic F127, PEG 400 and HPγCD) in combination with a low irradiation dose (5 J/cm(2); λmax: 450 nm) of constant irradiance and time. All the asymmetric curcuminoids, but only one of the glycosylated curcuminoids demonstrated substantial phototoxic effect on E.faecalis (⩾4.7 log reduction). Only two of the asymmetric curcuminoids showed a moderate to low phototoxic effect on the more persistent E.coli. This study emphasized that aromatic hydroxyl substituents in the para-position are important to maintain the phototoxic potential of curcuminoids independent of molecular symmetry. Glycosylation of the aromatic substituents resulted in a substantial loss in phototoxicity towards planktonic bacteria, an apparent change in the non-radiative S₁-decay process and a weaker interaction with Pluronic F127 compared to the non-glycosylated curcuminoids. The selected excipients Pluronic F127, PEG 400 and HPγCD strongly influenced the phototoxic potential of the unsymmetrical, non-glycosylated compounds.

Formulation and characterization of lyophilized curcumin solid dispersions for antimicrobial photodynamic therapy (aPDT): studies on curcumin and curcuminoids LII

CONTEXT

Bacterial resistance to antibiotics is increasing and alternative antibacterial treatments like antimicrobial photodynamic therapy (aPDT) are needed. Curcumin is under investigation as a potential photosensitizer in aPDT.

OBJECTIVE

The purpose of this study was to develop rapidly dissolving formulations of curcumin that could photoinactivate both Gram-positive and Gram-negative bacteria.

MATERIALS AND METHODS

Curcumin solid dispersions with methyl-β-cyclodextrin and hyaluronic acid (HA), hydroxypropyl methylcellulose (HPMC) or both HA and HPMC were prepared through lyophilization. The lyophilizates were characterized by curcumin drug load [% (w/w)], differential scanning calorimetry, photostability, thermal stability, their ability to form supersaturated solutions and by in vitro photoinactivation of Enterococcus faecalis and Escherichia coli.

RESULTS AND DISCUSSION

The lyophilizates were amorphous solid dispersions with a curcumin drug load in the range of 1.4-5.5% (w/w) depending on the included polymer and the ratio between curcumin and the cyclodextrin. The lyophilizates were photolabile, but thermally stable and dissolved rapidly in contact with water to form supersaturated solutions. Selected lyophilizates demonstrated >log 6 reduction of colony forming units/ml of both E. faecalis and E. coli after exposure to low curcumin concentrations (0.5-10 µM) and blue light dose (11-16 J/cm(2)). The high drug load of the lyophilizates, rapid dissolution, ability to form relatively stable supersaturated solutions and the very high phototoxicity towards both E. faecalis and E. coli make these lyophilizates suitable for in vivo aPDT.

CONCLUSIONS

This treatment with optimized curcumin formulations should be explored as an alternative to topical antibiotics in the treatment of wound infections.

Solid dispersions for preparation of phototoxic supersaturated solutions for antimicrobial photodynamic therapy (aPDT): Studies on curcumin and curcuminoides L

Curcumin is under investigation as a potential photosensitizer (PS) in antimicrobial photodynamic therapy (aPDT). The therapeutic potential of curcumin as a PS is limited by its low aqueous solubility, susceptibility to hydrolytic and photolytic degradation, and limited phototoxicity toward Gram negative (G-) bacteria. Supersaturated solutions of curcumin have demonstrated high phototoxicity toward several species of Gram positive (G+) bacteria as well as the G-Escherichia (E) coli. Thus, solid dispersions that can form supersaturated solutions of curcumin upon hydration may be beneficial in aPDT. In the present study, solid dispersions of curcumin have been prepared through lyophilization of concentrated solutions obtained from dissolution of hydroxypropyl-β-cyclodextrin (HPβCD)-curcumin co-precipitates. Hydroxypropyl methylcellulose (HPMC) was added to curcumin solutions prior to lyophilization. The resulting lyophilizates were porous, amorphous and hydrated and dissolved rapidly in contact with a model physiological salt solution. The detected drug load of the lyophilizates was in the range 0.5-1.0% (w/w) and was dependent on the selected ratio between HPβCD and curcumin in the co-precipitate. The lyophilizate with the highest drug load could easily be dissolved in aqueous medium to form curcumin solutions of relevant concentrations for aPDT (i.e., 10μM). Selected solutions of the curcumin solid dispersions showed a pronounced decrease in curcumin concentration up to 90% after storage for 168h, which indicated that supersaturated curcumin solutions were initially formed upon dissolution of the lyophilizates. Both freshly prepared and 2days old solutions of one selected curcumin lyophilizate induced significant inactivation of E. coli (∼1% bacterial survival) after exposure to a light dose of only 5J/cm(2).

Impact of curcumin supersaturation in antibacterial photodynamic therapy--effect of cyclodextrin type and amount: studies on curcumin and curcuminoides XLV

Curcumin has been investigated as a potential photosensitizer (PS) in antimicrobial photodynamic therapy (aPDT). The phototoxic effect of curcumin is dependent on proper formulations of the compound because of the lipophilic nature of the molecule and the extremely low water solubility at physiological conditions. In the present study, the combination of curcumin with either a methylated β-cyclodextrin (CD) or polyethylene glycol-based β-CD or γ-CD polymers was investigated in aPDT using Escherichia coli (E. coli) and Enterococcus faecalis as model bacteria. Solutions with various supersaturation ratios of curcumin were prepared with the selected CD or CD polymers. The concept of supersaturation was then investigated as a mean to enhance the phototoxic effect of curcumin, especially toward the gram-negative bacteria E. coli. A high supersaturation ratio corresponded with high phototoxicity of E. coli. Depending on the curcumin preparation, the bacterial survival ranged from 0.01% to no significant effect after irradiation with blue light (29 J/cm(2) ). Temporal stabilization of the supersaturated state is necessary in order to retain high and predictable photoreactivity of the PS. Further studies will be needed in order to formulate curcumin preparations with acceptable hydrolytic and photolytic stability and a temporal stabilization of a supersaturated state.

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.

Formulation and bacterial phototoxicity of curcumin loaded alginate foams for wound treatment applications: studies on curcumin and curcuminoides XLII

Curcumin loaded alginate foams are proposed for application in antimicrobial photodynamic therapy of infected wounds. The drug loaded foams were formulated to provide a burst release of the photosensitizer when hydrated. The foams remained intact after hydration and would be possible to remove from the wound prior to irradiation without causing any tissue damage. The characterization of the prepared foams showed that both curcumin loaded and unloaded foams hydrated within 1  min and absorbed from 12 to 16 times their dry weight of a model physiological fluid. Curcumin, the model photosensitizer, has an extremely low solubility in water and may aggregate in aqueous environment. Cyclodextrins (CDs) and polyethylene glycol 400 (PEG 400) were therefore selected as solubilizers of curcumin in the foams to provide a burst release of the photosensitizer. Exposure to the prepared foams in combination with visible light irradiation (∼9.7  J/cm(2)) resulted in >6  log reduction of Entrococcus faecalis cells. However, curcumin mediated photokilling of Escherichia coli was ineffective when CDs were selected as solubilizer of curcumin in the foams. An 81% reduction in viable E. coli cells was detected after treatment with the foam containing PEG 400 as the only solubilizer of curcumin combined with visible light irradiation (∼29  J/cm(2)).

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.

Toxicity evaluation of root canal sealers in vitro

AIM

To compare the toxicity of methacrylate resin-based root canal sealers with sealers based on epoxy resin and silicone by two-well established cell culture methods.

METHODOLOGY

Specimens of AH Plus, EndoREZ, RoekoSeal and Epiphany were prepared for direct contact in the Millipore filter diffusion test and as extracts in the MTT assay. Mouse fibroblasts (L929) were used as toxicity targets. Differences in cytotoxicity between fresh and set specimens and between the extracts of root canal sealers were determined by t-test (P < 0.05).

RESULTS

In the filter diffusion test, freshly mixed Epiphany and AH Plus were rated severely toxic and RoekoSeal and EndoREZ nontoxic. When set, Epiphany was moderately toxic, whereas AH Plus, RoekoSeal and EndoREZ were nontoxic. Epiphany was significantly more toxic than RoekoSeal and EndoREZ (P < 0.05). In the MTT assay with set specimens, Epiphany was rated severely toxic; AH Plus and RoekoSeal slightly toxic; and EndoREZ nontoxic. Epiphany was significantly more toxic than the other three materials in this test (P < 0.001).

CONCLUSION

The multi-methacrylate resin-based (Epiphany) root canal sealer was significantly more toxic to L-929 cells than the silicone-based Roeko Seal and the single methacrylate-based EndoREZ root canal sealers. AH Plus showed intermediate toxicity.