Studies on the toxicity of coal-tar dyes. I. Photodecomposed products of four xanthene dyes and their acute toxicity to fish

Quantification of permitted synthetic colours in food by liquid chromatographic methods: a review on analytical methods and their performance

Colours, natural and synthetic, are substances which add or restore colour to a food after processing or storage. They are widely used by food manufacturers but may pose a potential risk to human health. Most food safety authorities set up regulations to limit the use of synthetic colours, and monitor their levels and consumption by the general public. Therefore, validated analytical methods are needed to fulfil this requirement. This review presents a comprehensive overview of various liquid chromatographic methods used for quantification of permitted synthetic colours in foods. Available analytical methods have been assessed for their fitness for purpose in terms of extraction, clean-up, liquid chromatographic separation, quantification and method performance. The advantages and disadvantages are given of available analytical methods for analysing 24 synthetic colours, permitted for use by different jurisdictions. Gaps in the knowledge and levels of validation are identified and recommendations made on further research to develop suitable methods for routine monitoring of these permitted synthetic colours.

The employment of a removable chitosan-derivatized polymeric sensitizer in the photooxidation of polyhydroxylated water-pollutants

The known O2((1)∆g)-sensitizer system Chitosan bounded Rose Bengal (CH-RB), with Rose Bengal (RB) immobilized by irreversible covalent bonding to the polymer Chitosan (CH), soluble in aquous acidic medium, was employed in the photodegradation of three tri-hydroxy benzene water-contaminants (THBs). The system sensitizes the O2((1)∆g)-mediated photodegradation of THBs by a process kinetically favored, as compared to that employing free RB dissolved in the same solvent. Additionally the free xanthene dye, degradable by O2((1)∆g) through self-sensitization upon prolonged light-exposure, is considerably protected when bonded to CH-polymer. The polymeric sensitizer, totally insoluble in neutral medium, can be removed from the solution after the photodegradative cycle by precipitation through a simple pH change. This fact constitutes an interesting aspect in the context of photoremediation of confined polluted waters. In other words, the sensitizing system could be useful for avoiding to dissolve dyestuffs in the polluted waters, in order to act as conventional sunlight-absorbing dye-sensitizers. In parallel the interaction CH-O2((1)∆g) in acidic solution was evaluated. The polymer quenches the oxidative species with a rate constant 2.4 × 10(8) M(-1) s(-1) being the process mostly attributable to a physical interaction. This fact promotes the photoprotection of the bonded dye in the CH-RB polymer.

Ecotoxicity of xanthene dyes and a non-chlorinated bisphenol in soil

Soil eco-toxicity testing was conducted in support of Canada's Chemical Management Plan (CMP) to fill data gaps for organic chemicals known to primarily partition to soil, and of which the persistence and inherent toxicity are uncertain. Two compounds representative of specific classes of chemicals: non-chlorinated bisphenols containing an -OH group (4,4'-methylenebis(2,6-di-tert-butylphenol (Binox)) and xanthene dyes (2',4',5',7'-tetrabromo-4,5,6,7-tetrachloro-3',6'-dihydroxy-, disodium salt (Phloxine B), 2',4',5',7'-tetrabromofluorescein (TBF), 4',5'-dibromofluorescein (DBF), and 4,5,6,7-tetrachlorofluorescein (TCF)) were evaluated. The effect of these substances on plant growth (Elymus lanceolatus and Trifolium pratense) and soil invertebrate survival and reproduction (Folsomia candida and Eisenia andrei) were assessed using a field-collected sandy soil. Binox was persistent throughout testing (up to 63 d) with an average recovery of 77±2.9% at test end. Binox was not toxic to plants (IC50s>1076 mg kg(-1)) or E. andrei (IC50s>2651 mg kg(-1)); however, a significant reduction in F. candida adult survival and reproduction (IC50=89 (44-149) mg kg(-1)) was evident. Phloxine B was also persistent throughout testing, with an average recovery of 82±3.0% at test end. Phloxine B was significantly more toxic than Binox, with significant reductions in plant root growth (IC50s ≥ 11 mg kg(-1)) and invertebrate reproduction (IC50s ≥ 22 mg kg(-1)). DBF toxicity was not significantly different from that of Phloxine B for plant root growth (IC50s ≥ 30 mg kg(-1)), but was significantly less toxic for shoot growth (IC50s ≥ 1758 mg kg(-1)), and invertebrate adult survival (IC50s ≥ 2291 mg kg(-1)) and reproduction (IC50s ≥ 451 mg kg(-1)). A comparison between all four xanthene dyes was completed using F. candida, with the degree of toxicity in the order of Phloxine B ≥ TBF∼DBF>TCF. The results from these studies will contribute to data gaps for poorly understood chemicals (and chemical groupings) under review for environmental risk assessments, and will aid in the validation of model predictions used to characterize the fate and effects of these substances in soil environments.

Topical rose bengal: pre-clinical evaluation of pharmacokinetics and safety

BACKGROUND AND OBJECTIVES

Rose bengal (RB) is a potent photosensitizer that has largely been overlooked as a potential photodynamic therapy (PDT) agent. In this study, the feasibility of topical delivery of RB to the epidermis has been evaluated.

STUDY DESIGN/MATERIALS AND METHODS

Topical formulations of RB were assessed on murine and rabbit skin for pharmacokinetic properties, cutaneous toxicity, and photosensitization.

RESULTS

Hydrophilic formulations (<or=1% RB) exhibited rapid, selective, uniform delivery to the epidermis, with no significant acute cutaneous toxicity in normal skin. Illumination (532 nm) elicited no acute phototoxicity for light intensities <or=100 mW/cm(2) at a light dose of 100 J/cm(2); use of higher intensities resulted in superficial thermal damage. Repeat treatment of rabbit skin (weekly for four weeks) elicited minor phototoxicity only at the highest concentration (1% RB).

CONCLUSIONS

These results indicate that RB is safe for PDT treatment of skin disorders, exhibiting negligible effects in normal skin.