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Today, Alzheimer's disease (AD) as the most prevalent type of dementia turns into one of the most severe health problems. Neurofibrillary tangle (NFT), mostly comprised of fibrils formed by Tau, is a hallmark of a class of neurodegenerative diseases. Tau protein promotes assembly and makes stable microtubules that play a role in the appropriate function of neurons. Polyanionic cofactors such as heparin, and azo dyes, can induce aggregation of tau protein in vitro. Sunset Yellow is a food colorant used widely in food industries. In the current work, we introduced degradation product (DP) of Sunset Yellow as an effective inducer of Tau aggregation. Two Tau aggregation inducers were produced, and then the aggregation kinetics and the structure of 1N4R Tau amyloid fibrils were characterized using ThT fluorescence spectroscopy, X-Ray Diffraction (XRD), circular dichroism (CD) and atomic force microscopy (AFM). Also, the toxic effects of the induced aggregates on RBCs and SH-SY5Y cells were demonstrated by hemolysis and LDH assays, respectively. Both inducers efficiently accelerated the formation of the amyloid fibril. Along with the confirmation of the β-sheets structure in Tau aggregates by Far-UV CD spectra, X-ray diffractions revealed the typical cross-β diffraction pattern. The oligomer formation in the presence of DPs was also confirmed by AFM. The possible in vivo effect of artificial azo dyes on Tau aggregation should be considered seriously as a newly opened dimension in food safety and human health., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Sodium copper chlorophyllin (CHL) is a food colorant that exhibits many beneficial properties, including potential for use in radiotherapy. Nevertheless, genotoxicity studies investigating radioprotective properties against γ-radiation on human cells are rather scarce. The aim of this study was to assess the cytotoxicity, genotoxicity and induction of malondialdehyde formation on CHL pre-treated whole blood cells after an absorbed dose of 5 Gy γ-radiation. Irradiated whole blood cells pre-treated with 100, 500, and 1000 μg/mL CHL showed less DNA-strand breaks (10.92 ± 0.74%, 10.69 ± 0.68%, and 8.81 ± 0.69%, respectively) than untreated irradiated cells (12.58 ± 0.88%). At the same time, the level of malondialdehyde was lower in CHL pre-treated samples with 100, 500, and 1000 μg/mL CHL (14.11 ± 0.43, 16.35 ± 2.82, and 13.08 ± 1.03 μmol/L, respectively) compared to untreated irradiated samples (24.11 ± 0.25 μmol/L). Regarding cytotoxicity, no changes were observed in the samples tested. Another important finding is that CHL had no cyto/genotoxic properties toward human blood cells. Taken together, since CHL had no cyto/genotoxic effects and showed good radioprotective properties in human blood cells, further studies should be conducted in order to find its possible application in radiotherapy., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The human antimicrobial and immunomodulatory peptide LL-37 is ubiquitously expressed and secreted by epithelial cells of mucosal surfaces including the gastrointestinal tract, the primary absorption site of orally administered drugs and food components. Besides antimicrobial properties, LL-37 also contributes to the pathophysiology of various diseases such as ulcerative colitis, Crohn's disease and cancer. Non-covalent association of antiinflammatory drugs, porphyrin pigments, bile salts and food dyes to the peptide was uncovered and evaluated by circular dichroism (CD) spectroscopy. These agents induce the disorder-to-order conformational transition of the natively unstructured LL-37 leading to its helical folding. Even in the presence of chloride ions, when LL-37 is partially folded, the inducers were able to rise the α-helix content. CD titration data indicated positive cooperativity between the ligand molecules accommodated to the peptide chain resulting in multimeric complexes with apparent dissociation constants ranged from 2 to 500 μM. Computational docking suggested the prominent role of the Lys8-Arg19 segment in the accommodation of small molecules, governed principally by salt bridges and H-bonding. Since pleiotropic biological functions of LL-37 are strongly conformation-dependent, it could be anticipated that folding inducer compounds may modulate its in vivo actions and also of related cationic peptides., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The aim of this work is to try to substitute some synthetic additives by a natural extract from red prickly pear (Opuntia stricta) which known by its richness on bioactive polysaccharides mainly consisting of galactose, rhamnose and galacturonic acid. This natural fruit has a high content of carbohydrates above 18.81% FM. It contains also a high level of polyphenols 152.25 ± 0.26 μg QE/mg PPE and flavonoids about 370.60 ± 0.12 μg GAE/mg of PPE. In addition, prickly pear extract (PPE) displayed a strong antioxidant and antimicrobial activities. These activities are likely due to its phenolic, flavonoid and carbohydrate contents. Moreover, the addition of 2.5% of PPE, as a natural colorant and antimicrobial agent in salami formulation, causes a decrease in hardness and chewiness of the formulated salami. Interestingly, PPE inhibited bacterial growth in salami stored at 4 °C over 30 days. Sensorial analysis shows that the color, taste and texture of salami prepared with 2.5% of PPE are markedly more appreciated by panelists. Our results suggest that the betalain pigment, carbohydrate and phenolic compounds present in PPE could be used as a natural colorant, antioxidant and antimicrobial agent without change of the sensory characteristics., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Protein aggregation, a characteristic of several neurodegenerative diseases, displays vast conformational diversity from amorphous to amyloid-like aggregates. In this study, we have explored the interaction of tartrazine with myoglobin protein at two different pHs (7.4 and 2.0). We have utilized various spectroscopic techniques (turbidity, Rayleigh light scattering (RLS), intrinsic fluorescence, Congo Red and far-UV CD) along with microscopy techniques i.e. atomic force microscopy (AFM) and transmission electron microscopy (TEM) to characterize the tartrazine-induced aggregation in myoglobin. The results showed that higher concentrations of tartrazine (2.0-10.0mM) induced amorphous aggregation in myoglobin at pH 2.0 via electrostatic interactions. However, tartrazine was not able to induce aggregation in myoglobin at pH 7.4; because of strong electrostatic repulsion between myoglobin and tartrazine at this pH. The tartrazine-induced amorphous aggregation process is kinetically very fast, and aggregation occurred without the formation of a nucleus. These results proposed that the electrostatic interaction is responsible for tartrazine-induced amorphous aggregation. This study may help in the understanding of mechanistic insight of aggregation by tartrazine., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The aim of this study was to investigate the possible influence of halogenated compounds on thyroid hormone metabolism via inhibition of iodotyrosine deiodinase (IYD) activity. The structure-activity relationships of 44 halogenated compounds for IYD-inhibitory activity were examined in vitro using microsomes of HEK-293 T cells expressing recombinant human IYD. The compounds examined were 17 polychlorinated biphenyls (PCBs), 15 polybrominated diphenyl ethers (PBDEs), two agrichemicals, five antiparasitics, two pharmaceuticals and three food colorants. Among them, 25 halogenated phenolic compounds inhibited IYD activity at the concentration of 1×10(-4)M or 6×10(-4)M. Rose bengal was the most potent inhibitor, followed by erythrosine B, phloxine B, benzbromarone, 4'-hydroxy-2,2',4-tribromodiphenyl ether, 4-hydroxy-2,3',3,4'-tetrabromodiphenyl ether, 4-hydroxy-2',3,4',5,6'-pentachlorobiphenyl, 4'-hydroxy-2,2',4,5'-tetrabromodiphenyl ether, triclosan, and 4-hydroxy-2,2',3,4',5-pentabromodiphenyl ether. However, among PCBs and PBDEs without a hydroxyl group, including their methoxylated metabolites, none inhibited IYD activity. These results suggest that halogenated compounds may disturb thyroid hormone homeostasis via inhibition of IYD, and that the structural requirements for IYD-inhibitory activity include halogen atom and hydroxyl group substitution on a phenyl ring., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Previously, we reported that intratracheal administration of lipopolysaccharide elicited pulmonary hypertension (PH) in broilers reared under commercial conditions and in broilers reared in environmental chambers and pretreated with aerosolized red food colorant # 3 and propylene glycol (Red#3+PG), but not in control broilers reared in environmental chambers. The objective of the present experiment was to determine possible changes in the number or proportion of airway leukocytes that could contribute to the magnitude of the PH responses elicited in broilers. Birds were aerosolized for 40 min with a saturated mixture of Red#3+PG. After 24 h, a blood sample was taken, the broilers were killed, and a pulmonary lavage process was conducted in each bird. Leukocyte concentration (white blood cells/microL) and differential leukocyte counts (%) were measured in blood and lavage fluid. Leukocyte concentration in blood did not differ between groups, but the percentage of blood lymphocytes was lower in broilers from the Red#3+PG group compared with birds from the control group (52.4+/-2.9 and 56.9+/-2.9%, respectively). Cells recovered from the lavage fluid from both groups were primarily heterophils. The concentration of leukocytes was greater in the lavage fluid of broilers from the Red#3+PG group compared with broilers from the control group (763.2+/-158.7 and 402.9+/-62.6 white blood cells/microL, respectively), but the proportions among leukocytes were not different between the 2 groups. We propose that the increased concentration of leukocytes present within the airways was one of the components that enabled broilers pre-treated with aerosolized Red#3+PG to exhibit PH responses to intratracheal lipopolysaccharide.

Indigocarmine, which is widely used as a synthetic colouring agent for foods and cosmetics in many countries, was reduced to its leuco form and decolorized by rat liver microsomes with NADPH under anaerobic conditions. The reductase activity was enhanced in liver microsomes of phenobarbital-treated rats, and inhibited by diphenyliodonium chloride, a NADPH-cytochrome P450 reductase (P450 reductase) inhibitor, but was not inhibited by SKF 525-A or carbon monoxide. Indigocarmine reductase activity was exhibited by purified rat P450 reductase. In contrast, when indigocarmine was incubated with rat liver microsomes and NADPH under aerobic conditions, superoxide radical was produced and its production was inhibited by superoxide dismutase and diphenyliodonium chloride. When indigocarmine was incubated with purified rat P450 reductase in the presence of NADPH, superoxide radical production was enhanced 17.7-fold (similar to the enhancement of indigocarmine-reducing ability) as compared with that of rat liver microsomes. A decrease of one molecule of NADPH was accompanied with formation of about two molecules of superoxide radical. P450 reductase exhibited little reductase activity towards indigo and tetrabromoindigo, which also afforded little superoxide radical under aerobic conditions. These results indicate that indigocarmine is reduced by P450 reductase to its leuco form, and superoxide radical is produced by autoxidation of the leuco form, through a mechanism known as futile redox cycling.

Annatto preparations are used to impart distinctive flavor and color to foods and are a primary colorant in dairy foods such as cheese and butter. There are several reports indicating that certain fractions of the annatto plant have biological activities against microorganisms of significance in food fermentation, food preservation, and human health. However, little is reported describing the nature of the antimicrobial compound(s) or their potential presence in commercial annatto colorant preparations. This study was conducted to determine whether commonly available annatto extracts are capable of influencing the outgrowth of selected lactic acid, spoilage, and pathogenic microorganisms. Disk diffusion and tube macrodilution techniques were used to determine the MICs and MBCs of double-strength water-soluble annatto extracts. Standard antibiotic disks were used as controls for the disk diffusion assay. The results demonstrate that annatto has an inhibitory effect on Bacillus cereus, Clostridium perfringens, and Staphylococcus aureus, with MICs of 0.08, 0.31, and 0.16% (vol/vol) and diameters of inhibition of 9 to 10, 12 to 13, and 15 to 16 mm, respectively. A concentration of 0.63% (vol/vol) inhibited the growth of Streptococcus thermophilus, Lactobacillus casei subsp. casei, Lactococcus lactis, and Paenibacillus polymyxa. The MICs for Listeria monocytogenes and Enterococcus durans were 1.25 and 2.5% (vol/vol), respectively. No activity was detected against Lactobacillus plantarum, Bifidobacterium bifidum, yeasts, or selected gram-negative bacteria.

We have previously demonstrated the inhibitory effect of chlorophyllin, a green food additive, on the genotoxicities of various carcinogens in Drosophila. Recently, we reported that purpurin, a component of a red food additive produced from madder root (Rubia tinctorium), inhibits the bacterial mutagenicity of heterocyclic amines. In the present study, we examined antigenotoxic activities of various pigments that are either constituents of food or food additives, using Drosophila in vivo DNA repair assay. Third instar larvae of Drosophila were fed a mutagen with or without pigment. The resulting adult flies were monitored for their male (repair deficient)/female (repair proficient) ratios, which reflect the DNA damage. We tested a total of 20 pigments, which are mainly of plant origins, including flavonoids, carotenoids, anthocyanins, anthraquinones and beta-diketone (curcumin)-derivatives, against the genotoxicities of eight carcinogens; IQ, MeIQx, AFB1, NDMA, 2-AAF, DMBA, 4NQO, and MNU. Four anthraquinone pigments (alizarin, purpurin, lac color, and cochineal extract) showed significant antigenotoxic activities. Alizarin and purpurin suppressed the DNA damage induced by IQ, MeIQx, AFB1, NDMA, 2-AAF, DMBA, and MNU. Lac color and cochineal extract showed inhibition against IQ, MeIQx, AFB1, 2-AAF and DMBA. In these inhibitions, suppression of metabolic enzymes may be involved. Since purpurin and alizarin suppressed the activity of MNU, a direct alkylating agent, there may also be a mechanism distinct from enzyme inhibitions in these anthraquinone-mediated suppressions of DNA damage.

Extrinsic staining of teeth is a side-effect of some antiseptic mouthrinses. However, few of the many rinse products available to the general public have been investigated for their propensity to cause staining. Dietary factors play an aetiological role in staining and have been used in vitro to study and compare the activity of rinses. The aim of this study was to assess rinse products for staining in vitro and, through the staining reaction, to compare the activity of products containing the same ingredients. Perspex blocks, with or without saliva pretreatment, were soaked in rinses for 2 min, washed and placed in a standard tea solution for 60 min and then the optical density (OD) read on a spectrophotometer. The cycle was repeated 10 times for saliva and 17 times for no saliva specimens or until the maximum OD was exceeded. A series of three separate experiments was performed by this method. The maximum OD was not exceeded by any product before seven passages and therefore data were compared at six passages. For most products OD increased with saliva pretreatment. Some cetylpyridinium chloride (CPC) rinses stained comparably to a chlorhexidine rinse. CPC rinses, most of which contained the same concentration of the antiseptic, varied considerably in their propensity to induce staining and one was little different to water controls. A 0.1% chlorhexidine rinse stained slightly more than a 0.2%. A phenolic/essential oil product produced some staining but zinc, triclosan and other essential oil rinses did not stain.(ABSTRACT TRUNCATED AT 250 WORDS)

Although food additives may have a significant impact on the marketing and acceptability of food and may occasionally lead to side effects, the effect of these additives on the digestive process in humans is unknown. We evaluated whether adding coloring or monosodium glutamate to food increases the cephalic phase of gastric acid secretion or gastrin release. When ordinary food coloring or unusual food coloring was added, acid secretion and gastrin release were similar to a control study with no food coloring added. Moreover, addition of 360 mg monosodium glutamate to beef consomme soup had no effect on the acid secretory or gastrin response to the meal. Thus, the food additives studied led to no objective alteration in the gastric exocrine or endocrine response to food.

12 permitted food colours in use were screened for geno-toxicity. Mitotic gene conversion in Saccharomyces cerevisiae was used as the end-point. Each food colour was tested in stationary-phase as well as log-phase cells but without microsomal activation. These food colours did not cause any increase in mitotic gene conversion in diploid yeast BZ 34.

Incorporation of either turmeric (0.5%) or curcumin (0.015%) into diets of mice did not show significant effect on the incidence of micronucleated polychromatic erythrocytes, structural and numerical aberrations in bone-marrow chromosomes, pregnancy rate, number of live and dead embryos, total implants and mutagenic index. Also rats fed cooked diets containing turmeric (0.5 and 0.05%) did not show significant differences in the incidence of chromosomal aberrations in their bone marrow.

A methodology for investigating genotoxicity of food colours using the fluctuation and DNA-repair assays with bacteria is described. In addition, a liquid repair test, developed to permit incorporation of microsomes and the quantitative estimation of cell viability, has been characterised with a number of positive control agents. Results obtained in these systems suggest that the food colour Red 2G induces repairable DNA damage and base-substitution mutation, but only in the presence of a rat-liver microsomal preparation. The significance of the data in the light of other toxicological information is discussed.

Disodium 9-(3',4',5',6'-tetrachloro-o-carboxyphenyl)-6-hydroxy-2,4,5,7-tetrabromo-3-isoxanthone (phloxine), a red dye used as a food additive, was tested for its activity to induce 8-azaguanine (8AG) resistant mutations in cultured human embryonic cells. Phloxine had a severe cytotoxic effect on the cells at concentrations of 1 to 10 mug/ml. At concentrations of more than 30 mug/ml of phloxine no further decrease in cell survival was found. This cytotoxic effect of phloxine was not dependent on the duration of treatment. After treatment with phloxine for 2 h division of cells in normal medium was inhibited for 120 h. When cells were treated with phloxine at various concentrations for 2 h, cultured in normal medium for 48 h, and then selected with 30 mug/ml of 8AG, an increase in the induced mutation frequency was found. This increase in mutation frequency was dependent on the concentration of phloxine used as a mutagen and treatment with 100 mug/ml of phloxine increased the frequency to six times that in untreated cultures.

The cytotoxicity of 8 natural dyes, commercially available as food additives in Japan, was studied on cultured fetal rat hepatocytes. Laccaic acid, one of the carminic acid samples and monascus pigments were found to be very toxic to cultured hepatocytes. Laccaic acid caused an increase in gamma-glutamyl transpeptidase activity. An 11-fold increase was seen 4 days after such addition, a significantly greater elevation than that produced by either the water or acetone solvents employed, or other dyes which have no toxic effects. On the other hand, monascus pigments had an increasing effect on both gamma-glutamyl transpeptidase and glutathione S-transferase, the later enzyme being elevated approximately 9 times greater than control values within 2-4 days. The increases in gamma-glutamyl transpeptidase and glutathione S-transferase activities by laccaic acid and monascus pigments could be inhibited by the simultaneous addition of either actinomycin D or cycloheximide. This suggests that the induction of these enzymes requires transcription and translation processes.

The food colour Brown FK (EEC Serial No. 124) is a mixture of p-sulphophenylazo derivatives of m-toluylenediamine and m-phenylenediamine and is used in the UK for colouring kippers. Brown FK and its constituents were assayed for mutagenicity in Salmonella typhimurium TA 1535, TA 1537 and TA 1538. Samples of Brown FK from three manufacturers were mutagenic in TA 1538 (framshift mutant) when activated by a rat-liver supernatant fraction. Mutagenicity was linearly dose-dependent in the range of 0--3 mg/plate with activities ranging from 22 to 50 times the spontaneous mutation frequency. One sample of Brown FK was mutagenic in the absence of metabolic activation producing a 16-fold increase in mutation at 4 mg/plate. Two major constituents of Brown FK, 2,4-diamino-5-(p-sulphophenylazo)-toluene (I) and 1,3-diamino-4-(p-sulphophenylazo)benzend (II), each present at about 18% in the complete colour, were mutagenic in TA 1538. Mutagenicity was linearly dose-related in the range 0--1 mumol/plate, with slopes of 0.35 mutants/nmol for compound I and 1.5 mutants/nmol for compound II. This activity was dependent on metabolic activation. Four other major constituents, (di- and tri-substituted diamines) were inactive, as was sulphanilic acid, the major excretion product of Brown FK. The mutagenicity of Brown FK could be largely accounted for by the combined effects of compounds I and II. Earlier studies showed that compounds I and II were responsible for the acute myotoxic effects seen when Brown FK was given per os to rats and pigs. Azoreductive fission of I and II to reactive triamines by gut microflora was thought to be the main metabolic pathway by which Brown FK produced its myotoxic effects, and it is proposed that the mutagenic effects of Brown FK are probably mediated by a similar mechanism.

Erythrosine (diNa, tetraiodofluorescein) was nonmutagenic to the Ames/Salmonella typhimurium strains TA97a, TA98, TA100, TA102, and TA104, to a concentration of 2 mg/plate. No mutative intermediates were detected on metabolism by rat caecal cell-free extracts or rat liver S9 mixture; or on incubation with the comutagens, harman and norharman (+/- S9). Instead, an unexpected dose-dependent suppression in spontaneous reversion frequencies was observed (maximum approximately equal to 35% decrease). Erythrosine was antimutagenic to benzo[a]pyrene, but it did not decrease the mutagenicity of the other adduct-forming mutagen, 4-nitroquinoline N-oxide. The food dye was strongly antimutagenic to the bifunctional alkylating agent, mitomycin C, though it did not exhibit a similar effect on the mutagenicity of the corresponding monofunctional agent, methyl methanesulphonate. It partially depressed the mutagenic potentials of sodium azide. The antimutagenic effect of erythrosine on an intercalating agent, ethidium bromide, was discernible only at the highest dose (2 mg/plate). These results have been interpreted in terms of a genointeractive role of erythrosine. Erythrosine produced differential toxic effects in repair-deficient (TA97a, TA98, TA100) and repair-proficient (TA102, TA104) Salmonella tester strains; survival of the repair-deficient strains was found to be decreased. Photoinduced potentiation of erythrosine toxicity was observed, although light irradiation in the presence of erythrosine did not modify the reversion frequencies of the tester strains. The evidence strongly suggests that erythrosine, which exhibits nonmutagenicity in the Ames/Salmonella test, can interact with DNA repair enzymes and/or with DNA.

Carmoisine (C.I. (1956) No. 14720) was fed at levels of 0, 0.35, 0.8 and 2.0% in the diet of rats throughout a multigeneration reproduction study. The dye had not untoward effects on reproduction capacity of any of the generations studied. Fertility, lactation and viability indices of all groups fed carmoisine did not differ significantly from controls at any stage of the study. These results indicate a maximum no-effect level of 2% in the diet. Data from an additional nine-week feeding study (dietary levels were 0, 2, 4, 6 and 8%) suggest that the no-effect level may in fact be even higher since 4% carmoisine in the diet was tolerated without evidence of overt toxicity.

The mutagenicity of 4 azo dyes (FD&C Yellow No. 5, FD&C Yellow No. 6, FD&C Red No. 40 and amaranth) that are widely used to color food has been evaluated. 4 different methods were used: (1) the standard Ames plate-incorporation assay performed directly on the dyes in the absence of S9 and in the presence of rat- or hamster-liver S9; (2) application of the standard plate assay to ether extracts of aqueous solutions of the dyes; (3) a variant of the standard assay, using hamster liver S9, preincubation, flavin mononucleotide (FMN) and other modifications designed to facilitate azo reduction; and (4) reduction of the dyes with sodium dithionite, followed by ether extraction and the standard plate assay. Assays that include chemical reduction (methods 3 and 4) were included because azo compounds ingested orally are reduced in the intestine with the release of free aromatic amines. No mutagenic activity was seen for any of the azo dyes tested by using the standard Ames plate assay (method 1). Ether extracts of some samples of FD&C Yellow No. 6, FD&C Red No. 40 and amaranth were active (method 2), but only at high doses, generally 250 mg-equivalents or more per plate. These results indicate the presence of low levels of ether-extractable mutagenic impurities. The FMN preincubation assay (method 3) gave negative results for all dye samples tested. Most batches of FD&C Red No. 40 tested had mutagenic activity that was detectable when the ether extract of less than 1 mg of dithionite-reduced dye was plated in the presence of S9 (method 4). This finding implies that an impurity in these samples of FD&C Red No. 40 can be reduced to yield an ether-extractable mutagen. Dithionite-reduced samples of FD&C Yellow No. 6 and amaranth showed ether-extractable mutagenic activity only at much higher doses than those at which activity was seen with most dithionite-reduced samples of FD&C Red No. 40 (method 4). FD&C Yellow No. 5 showed no mutagenic activity with this method. Mutagenic activity was not detected when FD&C Red No. 40 was tested by using the azo reduction preincubation assay with FMN (method 3).(ABSTRACT TRUNCATED AT 400 WORDS)

The genetic toxicology of the major dyestuffs used in foods, drugs and cosmetics has been reviewed. Published data for azo, triphenylmethane and xanthene dyes from short-term assays for muta-carcinogenicity have been summarized and discussed according to usage, current and previous worldwide legislative status. Certain other synthetic food dyes, commercial mixtures, natural and polymeric colourants as well as a section on aminoazobenzene and its derivatives have been included. Genotoxicity has been discussed with reference to structural chemistry, levels of exposure, absorption and metabolism and to epidemiological information. The extent of agreement between data from different tests and correlations with animal cancer assays have been considered. Synthetic dyes from the 3 major structural classes exhibit genotoxicity, whilst only 2 natural colours have proved active. Activity may be due to the presence of certain functional groups, notably nitro- and amino-substituents which are metabolized to ultimate electrophiles that may be stabilized by electronic interaction with aryl rings. Metabolic processes such as azo-reduction may be activating or detoxifying. the low but significant correlation between animal carcinogenicity and short-term test data may be increased with further screening, especially involving chromosome assays. It is suggested that a human cancer hazard may exist where significant quantities of finished benzidine dye samples are handled. Such risks from exposures to other colours and the possibility of human germ-line mutation induction by dyestuffs cannot be meaningfully assessed.

Thirty-seven azo, xanthene and triphenylmethane dyes including FD and C colors currently approved for use in the U.S.A. and a number of delisted food colors, were tested in the Salmonella/microsome system. In addition to direct plate tests with five tester strains (TA1535, TA100, TA1537, TA1538, TA98), the azo dyes were also assayed after chemical reduction to their component amines. Also, a selected group of azo dyes was subjected to liquid tests (both aerobic with microsomes and anaerobic) and to plate tests involving initial 16 h anaerobic incubations to facilitate microbial reduction of the azo bond. None of the presently listed FD and C colors was mutagenic in any of the test modifications. Among formerly listed colors only Butter Yellow (p-dimethylaminoazobenzene), a recognized animal carcinogen, was mutagenic in the aerobic liquid test. Several other azo dyes were either directly mutagenic, viz. Acid Alizarin Yellow R and Alizarin Yellow GG; required microsomal activation, viz. Acid Alizarin Red B and Methyl Red; or required chemical reduction and microsomal activation, viz. Acid Alizarin Violet N and Sudan IV. Of the non-azo dyes tested only two xanthene dyes appeared to be mutagenic, viz. 9-(2-sulfophenyl)-6-hydroxy-3-isoxanthenone and its 2,4,5,7-tetrabromo derivative.

Rat fed carmoisine (C.I. (1956) No. 14720) at 0.35, 0.8 or 2.0% in the diet for 52 weeks showed no adverse effects of the dye when compared to control animals. Mortality, weight gain, hematological values and relative organ weights were the same in control and treated animals. There was no increase in tumor incidence due to carmoisine treatment. Male rats fed 2.0% carmoisine showed an increased incidence of several mild subclinical conditions (minimal bronchitis and tracheal inflammation). Because of this occurrence, the maximum no-effect level after 1 year exposure appears to be 0.8%, equivalent to a daily intake of approx. 400 mg/kg.