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Formation and structural modification of oxygenated polycyclic aromatic hydrocarbons (oxyPAHs) by UV irradiation on minerals have recently been proposed as a possible channel of PAH transformation in astrochemical and prebiotic scenarios of possible relevance for the origin of life. Herein, it is demonstrated that high-energy proton-beam irradiation in the presence of various meteorites, including stony iron, achondrite, and chondrite types, promotes the conversion of two representative oxyPAH compounds, 1-naphthol and 1,8-dihydroxynaphthalene, to complex mixtures of oxygenated and oligomeric derivatives. The main identified products include polyhydroxy derivatives, isomeric dimers encompassing benzofuran and benzopyran scaffolds, and, notably, a range of quinones and perylene derivatives. Addition of urea, a prebiotically relevant chemical precursor, expanded the range of identified species to include, among others, quinone diimines. Proton-beam irradiation of oxyPAH modulated by nitrogen-containing compounds such as urea is proposed as a possible contributory mechanism for the formation and processing of insoluble organic matter in meteorites and in prebiotic processes.
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Self-patterning processes originated by physical stimuli have been extensively documented in thin films, whereas spontaneous wrinkling phenomena due to chemical transformation processes are, to the best of our knowledge, unprecedented. Herein we report a case of spontaneous polymerization-driven surface nano-patterning (â¼500 nm) that develops in smooth thin solid films of 5,6-dihydroxyindole (DHI), a major precursor of eumelanin polymers, over a time scale of 30 to 60 days in air at room temperature. The phenomenon can be observed only above a critical film thickness of â¼250 nm and it is affected by exposure to ammonia vapors causing acceleration of the oxidation process. The thickness-dependent onset of wrinkling can be attributed to non-homogeneous rates of oxidation through the film causing slow swelling/expansion of the inner layers followed by fast stiffening and cross-linking in the outer layer exposed to higher oxygen levels.
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Nanoscale disassembly of mussel-inspired polydopamine (PDA) in ionic liquids (ILs) was recently shown to induce an electron paramagnetic resonance (EPR)-detectable reorganization of free radical centers in the resulting nanoparticles (NPs) in an IL-controlled manner. Herein, we report electrical impedance spectroscopy (EIS) data showing that PDA NPs produced by suspending samples obtained in Tris and bicarbonate buffer (PDA-T and PDA-C) in different ILs display different redox activity as a result of structural control combined with IL-surface interactions. In particular, susceptibility to oxidation was found to correlate closely with the spin density in an ion pair-tunable fashion in ILs. Structural control over free radical properties and redox behavior of PDA NPs in ILs opens novel perspectives for the rational design of functional nanovectors of possible interest for drug delivery and theranostic applications.
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Astrochemistry and astrobiology, the fascinating disciplines that strive to unravel the origin of life, have opened unprecedented and unpredicted vistas into exotic compounds as well as extreme or complex reaction conditions of potential relevance for a broad variety of applications. Representative, and so far little explored sources of inspiration include complex organic systems, such as polycyclic aromatic hydrocarbons (PAHs) and their derivatives; hydrogen cyanide (HCN) and formamide (HCONH2) oligomers and polymers, like aminomalononitrile (AMN)-derived species; and exotic processes, such as solid-state photoreactions on mineral surfaces, phosphorylation by minerals, cold ice irradiation and proton bombardment, and thermal transformations in fumaroles. In addition, meteorites and minerals like forsterite, which dominate dust chemistry in the interstellar medium, may open new avenues for the discovery of innovative catalytic processes and unconventional methodologies. The aim of this review was to offer concise and inspiring, rather than comprehensive, examples of astrochemistry-related materials and systems that may be of relevance in areas such as surface functionalization, nanostructures, and hybrid material design, and for innovative technological solutions. The potential of computational methods to predict new properties from spectroscopic data and to assess plausible reaction pathways on both kinetic and thermodynamic grounds has also been highlighted.
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Exobiología/métodos , Animales , Formamidas/química , Humanos , Cianuro de Hidrógeno , Nanoestructuras/química , Nitrilos/química , Hidrocarburos Policíclicos Aromáticos/químicaRESUMEN
Due to the emerging biomedical relevance and technological potential of fungal melanins, and prompted by the virtual lack of information about their structural arrangement, an optimized synthetic protocol has been devised for a potential structural model of Ascomyces allomelanin through enzyme-catalyzed oxidative polymerization of 1,8-dihydroxynaphthalene (1,8-DHN). Electrospray ionization mass spectrometry (ESI-MS) measurements of freshly synthesized DHN-polymer recorded in the negative ion mode allowed detection of oligomers up to m/z 4000, separated by 158â Da, corresponding to the in-chain DHN-unit. The dominant peaks were assigned to singly-charged distribution, up to 23 repeating units, whereas a doubly charged polymer distribution was also detectable. Chemical derivatization, ultra-performance liquid chromatography (UPLC)-ESI MS, and MS/MS data confirmed that oxidative polymerization of 1,8-DHN proceeds through C-C coupling of the naphthalene rings. The new insights reported here into synthetic 1,8-DHN oligomers/polymers as a mimic of fungal melanins may guide novel interesting advances and applications in the field of biomimetic functional materials.
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Materiales Biomiméticos/química , Proteínas Fúngicas/metabolismo , Hongos/metabolismo , Melaninas/metabolismo , Naftoles/química , Biocatálisis , Materiales Biomiméticos/metabolismo , Cromatografía Líquida de Alta Presión , Proteínas Fúngicas/química , Peroxidasa de Rábano Silvestre/metabolismo , Melaninas/química , Oxidación-Reducción , Polimerizacion , Espectrometría de Masa por Ionización de Electrospray , Espectrometría de Masas en TándemRESUMEN
Although it has long been known that the peculiar electronic-ionic conductor behavior of eumelanin is critically dependent on hydration, the detailed mechanisms by which water-polymer interactions control and affect the conduction properties have remained largely obscure. In this paper, we report a remarkable anisotropy and giant polarization effect in a synthetic eumelanin (TEGMe) chemically functionalized with hydrophilic TEG residues. FT-IR analyses of water sorption isotherms and AC measurements were consistent with a microporous structure binding or hosting mainly isolated water molecules. In contrast, similar experiments on a commercial synthetic eumelanin (AMe) used as a reference were suggestive of a bulk macroporous scaffold binding or hosting liquid water. These data disclosed for the first time the differential impact on eumelanin conductivity of vapor, liquid and ice-like forms of water adsorbed onto or embedded into the polymer layer. It is thus demonstrated, for the first time, that hydration controls the conduction properties of eumelanin in a more complex manner than is commonly believed, involving, besides the reported semiquinone comproportionation equilibria, the mode of interaction of water molecules as governed by both the chemical and morphological features of the polymer.
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The oxidative polymerization of 5,6-dihydroxybenzothiophene (DHBT), the sulfur analog of the key eumelanin building block 5,6-dihydroxyindole (DHI), was investigated to probe the role of nitrogen in eumelanin build-up and properties. Unlike DHI, which gives a typical black insoluble eumelanin polymer on oxidation, DHBT is converted to a grayish amorphous solid (referred to as thiomelanin) with visible absorption and electron paramagnetic resonance properties different from those of DHI melanin. Mass spectrometry experiments revealed gradational mixtures of oligomers up to the decamer level. Quite unexpectedly, nuclear magnetic resonance (NMR) analysis of the early oligomer fractions indicated linear, 4-, and 7-linked structures in marked contrast with DHI, which gives highly complex mixtures of partially degraded oligomers. Density functional theory (DFT) calculations supported the tendency of DHBT to couple via the 4- and 7-positions. These results uncover the role of nitrogen as a major determinant of the structural diversity generated by the polymerization of DHI, and point to replacement by sulfur as a viable entry to regioregular eumelanin-type materials for potential applications for surface functionalization by dip coating.
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Melaninas/química , Nitrógeno/química , Polímeros/química , Azufre/química , Antioxidantes/química , Isomerismo , Modelos Moleculares , Estructura Molecular , Oxidación-Reducción , Polimerizacion , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Análisis EspectralRESUMEN
5,6-Dihydroxyindole (1) and its N-methyl derivative (2), key eumelanin building blocks, were inserted into zeoliteâ L by sublimation at 175 °C for 5 days. At a 10â mg/300â mg indole/zeolite ratio, the resulting hybrids displayed a stable deep red coloration. CP/MAS (13)Câ NMR and UV/Vis spectroscopy of the red species suggested the generation and accommodation of quinonoid biindole derivative(s) within the void space of the acidic zeolite channels. Removal of the zeolite matrix by treatment with HF gave a stable species that could be separated by HPLC and characterized by mass spectrometry as an oxygenated biindole derivative (or a mixture of isomers), suggesting addition of water to the original dimer and subsequent re-oxidation. The characterization was corroborated by optimized molecular geometries and simulated UV spectra with density functional calculations. Loading 1 or 2 into the larger pores of SBA-15 type mesoporous silica resulted in black eumelanin-type polymers, confirming channel size dependence over the polymerization process.
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Indoles/química , Melaninas/química , Zeolitas/química , Polimerizacion , PorosidadRESUMEN
In view of a continuous trend in replacing synthetic feed additives and especially flavouring compounds by botanical preparations, different aspects of the safety evaluations of plants and plant-derived preparations and components in feed are discussed. This includes risk assessment approaches developed by the European Food Safety Authority (EFSA) for phytotoxins regarding unintentional exposure of target animals and of consumers to animal derived food via carry-over from feed. Relevant regulatory frameworks for feed additives and feed contaminants in the European Union are summarised and the essentials of existing guidelines used in the safety evaluation of botanicals and their preparations and components in feed are outlined. The examples presented illustrate how the safety of the botanicals, their preparations and components present in feed is assessed. An outlook on possible future developments in risk assessment by applying new in vitro and in silico methodologies is given.
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Alimentación Animal , Unión Europea , Medición de Riesgo , Alimentación Animal/análisis , Animales , Humanos , Contaminación de Alimentos/análisis , Inocuidad de los Alimentos , Aditivos Alimentarios/toxicidad , Aditivos Alimentarios/análisisRESUMEN
Melanins are pigments employed in food, cosmetic, and textile industries, manufactured by extraction from cuttlefishes. Their biotechnological production by Streptomycetes, instead, has been poorly investigated so far. In this paper, for the first time, the strain Streptomyces nashvillensis DSM 40314 was tested as an extracellular melanin producer by investigating the influence of diverse temperatures (26, 28, and 30 °C) and pH values (6.0 and 7.0) on bacterial growth, melanin production, and on the activity of the secreted tyrosinase, the first enzyme of the pigment biosynthetic pathway. In physiological 96-h shake flask experiments, the optimal growth parameters resulted to be 28 °C and pH 7.0, at which a maximum biomass of 8.4 ± 0.5 gcdw/L, a melanin concentration of 0.74 ± 0.01 g/L (yield on biomass of 0.09 ± 0.01 g/gcdw and productivity of 0.008 ± 0.001 g/L/h), and a final tyrosinase activity of 10.1 ± 0.1 U/mL were reached. The produced pigment was purified from the broth supernatant with a two-step purification process (75.0 ± 2.0% of purity with 65.0 ± 5.0% of recovery) and tested for its chemical, antioxidant, and photoprotective properties. Finally, characterization by UV-visible and FT-IR spectroscopy, elemental analyses, and mono- and bi-dimensional NMR suggested the eumelanin-like nature of the pigment.
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Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of citronella oil obtained from the leaves of Cymbopogon nardus (L.) Rendle, when used as a sensory additive for all animal species. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that citronella oil from C. nardus is of low concern for long-living and reproductive animals at the use levels in complete feed of 3.5 mg/kg for laying hens and rabbits, 6 mg/kg for sows and dairy cows, 9.5 mg/kg for sheep/goats and horses, 2.0 mg/kg for cats and 10 mg/kg for dogs. For short-living animals (species for fattening), the additive was considered of no concern at concentrations of 18 mg/kg in chickens for fattening, 24 mg/kg in turkeys for fattening, 20 mg/kg for piglets, pigs for fattening, veal calves (milk replacer), cattle for fattening, sheep/goats for meat production, horses for meat production and rabbits for meat production, and 30 mg/kg for salmonids. The conclusions were extrapolated to physiologically related minor species. For any other species, the additive is considered of low concern at 2.0 mg/kg complete feed. The use of citronella oil in animal feed is expected to be of no concern for the consumers and for the environment. The essential oil under assessment should be considered as irritant to skin and eyes and as a dermal sensitiser. When handling the essential oil, exposure of unprotected users to methyleugenol may occur. Therefore, to reduce the risk, the exposure of the users should be minimised. Since the leaves of C. nardus and its preparations were recognised to flavour food and its function in feed would be essentially the same as that in food, no further demonstration of efficacy was considered necessary.
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Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of a tincture from the leaves of Eucalyptus globulus Labill. (eucalyptus tincture) when used as a sensory additive for all animal species. The product is a â â â â â solution, with a dry matter content of ~ 1.86%, which contains on average 0.454% phenolic acids and flavonoids (of which 0.280% was gallic acid), 0.0030% 1,8-cineole and 0.00012% methyleugenol. In the absence of analytical data on the occurrence of mono- or diformylated adducts of acylphloroglucinols with terpenes in the tincture and in the absence of toxicity data, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) could not conclude on the use of eucalyptus tincture for long-living and reproductive animals. For short-living animals (species for fattening), the additive was considered of no concern at 4 mg/kg complete feed for chickens for fattening, 5 mg/kg for turkeys for fattening, 6 mg/kg for piglets and rabbits for meat production, 7 mg/kg for pigs for fattening, 16 mg/kg for veal calves (milk replacer), 14 mg/kg for cattle for fattening, sheep/goats and horses for fattening, and 15 mg/kg for salmonids. These levels were extrapolated to physiologically related minor species. No safety concern would arise for the consumer from the use of eucalyptus tincture up to the levels in feed considered of no concern. Eucalyptus tincture should be considered as irritant to skin and eyes, and as a dermal and respiratory sensitiser. The use of eucalyptus tincture as a flavour in animal feed was not expected to pose a risk for the environment. Since the leaves of E. globulus and their preparations were recognised to flavour food and their function in feed would be essentially the same, no demonstration of efficacy was considered necessary.
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Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of tinctures obtained from the dried leaves of Ginkgo biloba L. (ginkgo tinctures) when used as sensory additives. The tinctures are water/ethanol solutions with a dry matter content of 5.7% (tincture A) and 3.0% (tincture B). The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the additives under assessment are safe for the target species at the following concentrations in complete feed: (i) ginkgo tincture A at 240 mg/kg for horses and 750 mg/kg for dogs; (ii) ginkgo tincture B at 600 mg/kg for horses and 50 mg/kg for all other animal species. No safety concern would arise for the consumer from the use of ginkgo tinctures up to the maximum proposed use level in feed for the target species. The tinctures should be considered as irritants to skin and eyes, and as dermal and respiratory sensitisers. The use of ginkgo tinctures at the proposed use levels in feed for the target species is not considered to be a risk to the environment. While the available data indicate that Ginkgo preparations have a distinctive flavour profile, there is no evidence that ginkgo tinctures would impart flavour to a food or feed matrix. Therefore, the FEEDAP Panel cannot conclude on the efficacy of the additives.
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Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of a tincture from the dried flower bud of Syzygium aromaticum (L.) Merr. & L.M. Perry (clove tincture) when used as a sensory additive in feed and water for drinking for all animal species. The product is a â â â â â ) solution, with a dry matter content of ~ 1.66%. The product contains on average 0.511% phenolic acids (of which 0.0344% were flavonoids), 0.039% eugenol, 0.00019% methyleugenol and 0.00008% estragole. The Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the use of clove tincture is very unlikely to be of safety concern for the target species up to the maximum proposed use level of 50 mg clove tincture/kg complete feed for all animal species, except for horses, for which the proposed use level is 200 mg/kg complete feed. The FEEDAP Panel considers that the use in water for drinking alone or in combination with use in feed should not exceed the daily amount that is considered very unlikely to be of safety concern when consumed via feed alone. No safety concern would arise for the consumer and the environment from the use of clove tincture up to the maximum proposed use levels in feed. The additive under assessment should be considered as irritant to skin and eyes, and as a dermal and respiratory sensitiser. When handling the additive, exposure of unprotected users to methyleugenol and estragole may occur. Therefore, to reduce the risk, the exposure of the users should be minimised. Since the flower buds of S. aromaticum and their preparations were recognised to flavour food and their function in feed would be essentially the same, no demonstration of efficacy was considered necessary.
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Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of an essential oil obtained from the wood of Juniperus deppeana Steud. (cedarwood Texas oil), when used as a sensory additive for all animal species. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the essential oil under assessment is safe up to the maximum proposed use levels in complete feed of 15 mg/kg for veal calves (milk replacer), cattle for fattening, sheep, goats, horses, dogs, salmonids and ornamental fish. For the other species, the calculated safe concentrations in complete feed were 5 mg/kg for chickens for fattening, 8 mg/kg for laying hens, 7 mg/kg for turkeys for fattening, 10 mg/kg for piglets, 12 mg/kg for pigs for fattening, 14 mg/kg for sows and dairy cows, 8.5 mg/kg for rabbits and 4 mg/kg for cats. These conclusions were extrapolated to other physiologically related species. For any other species, the additive was considered safe at 4 mg/kg complete feed. The use of cedarwood Texas oil in water for drinking was considered safe provided that the total daily intake of the additive does not exceed the daily amount that is considered safe when consumed via feed. No concerns for consumers and the environment were identified following the use of the additive up to the maximum proposed use level in feed. The additive under assessment should be considered as irritant to skin and eyes, and as a skin and respiratory sensitiser. Since the individual components of cedarwood Texas oil are recognised to flavour food and their function in feed would be essentially the same as that in food, no further demonstration of efficacy was considered necessary.
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Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of an essential oil obtained from the fruit of Carum carvi L. (caraway oil), when used as a sensory additive in feed and water for drinking for all animal species. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) Panel concluded that the use of caraway oil is of no concern up to the following concentrations in complete feed: 9 mg/kg for chickens for fattening, 13 mg/kg for laying hens, 12 mg/kg for turkeys for fattening, 16 mg/kg for piglets, 19 mg/kg for pigs for fattening, 24 mg/kg for sows, 35 mg/kg for veal calves (milk replacer), 11 mg/kg for cattle for fattening, 10 mg/kg for dairy cows, sheep, goats, horses and rabbits, 25 mg/kg for salmonids and dogs. These conclusions were extrapolated to other physiologically related species. For cats, ornamental fish and other species, no conclusion can be drawn. The use of caraway oil in animal feed under the proposed conditions of use is safe for the consumer and the environment. The additive under assessment should be considered as an irritant to skin and eyes, and as a respiratory and skin sensitiser. When handling the essential oil, exposure of unprotected users to perillaldehyde may occur. Therefore, to reduce the risk, the exposure of the users should be minimised. Since C. carvi and its preparations were recognised to flavour food and its function in feed would be essentially the same as that in food, no further demonstration of efficacy was considered necessary.
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Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety of microcrystalline cellulose and carboxymethyl cellulose as technological feed additives for all animal species. In its previous opinions on the safety and efficacy of the products, the FEEDAP Panel could not conclude on proper identification and characterisation as required for a feed additive. The occurrence of potential toxic impurities could also not be assessed. Based on the new data provided, the feed additives microcrystalline cellulose and carboxymethyl cellulose were properly identified and characterised and were shown to meet the specifications set for their use as food additives. Therefore, the conclusions of the safety reached in the previous opinions for microcrystalline cellulose and carboxymethyl cellulose meeting the food additive specifications apply to the microcrystalline cellulose and carboxymethyl cellulose under assessment as feed additives. The additives are considered safe for all animal species, the consumer and the environment. In the absence of data, the FEEDAP Panel is not in the position to conclude on the safety for the user.
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Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety of hydroxypropyl cellulose as a technological feed additive for all animal species. In its previous opinions on the safety and efficacy of the product, the FEEDAP Panel could not conclude on proper identification and characterisation as required for a feed additive. The occurrence of potential toxic impurities could also not be assessed. Based on the new data provided, the feed additive hydroxypropyl cellulose was properly identified and characterised and was shown to meet the specifications set for the food additive. Therefore, the conclusions of the safety assessment reached in the previous opinion for hydroxypropyl cellulose meeting the food additive specifications, apply to the hydroxypropyl cellulose under assessment as a feed additive. The feed additive is considered safe for all animal species, the consumer and the environment. In the absence of data, the FEEDAP Panel is not in the position to conclude on the safety for the user.
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Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety of ethyl cellulose as a technological feed additive for all animal species. In its previous opinions on the safety and efficacy of the product, the FEEDAP Panel could not conclude on proper identification and characterisation as required for a feed additive. The occurrence of potential toxic impurities could also not be assessed. Based on the new data provided, the feed additive ethyl cellulose was properly identified and characterised and was shown to meet the specifications set for the food additive. Therefore, the conclusions of the safety assessment reached in the previous opinions for ethyl cellulose meeting the food additive specifications, apply to the ethyl cellulose under assessment as a feed additive. The feed additive is considered safe for all animal species, the consumer and the environment. In the absence of data, the FEEDAP Panel is not in the position to conclude on the safety for the user.
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Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety of hydroxypropyl methyl cellulose and methyl cellulose as technological feed additives for all animal species. In its previous opinions on the safety and efficacy of the products, the FEEDAP Panel could not conclude on proper identification and characterisation as required for a feed additive. The occurrence of potential toxic impurities could also not be assessed. Based on the new data provided, the feed additives hydroxypropyl methyl cellulose and methyl cellulose were properly identified and characterised and were shown to meet the specifications set for the food additives. Therefore, the conclusions of the safety assessments reached in the previous opinions for hydroxypropyl methyl cellulose and methyl cellulose meeting the food additive specifications, apply to the hydroxypropyl methyl cellulose and methyl cellulose under assessment as feed additives. The additives are considered safe for all animal species, the consumer and the environment. In the absence of data, the FEEDAP Panel is not in the position to conclude on the safety for the user.