The natural anthraquinone dye emodin: Eco/genotoxicological characterization for aquatic organisms.

Emodin is an anthraquinone secondary metabolite produced by several species of plants and fungi. Emodin is known for its pharmacological versatility, and, in the textile industry, for its good dyeing properties. However, its use in the textile industry can result in the formation and disposal of large volumes of wastewater. Emodin mutagenicity has been shown in bacteria and in human cells, but little is known about its possible toxic, genotoxic, or mutagenic effects in aquatic organisms. We have evaluated the eco/genotoxicity of emodin to aquatic organisms. Emodin was toxic to Daphnia similis (EC50 = 130 µg L-1) and zebrafish embryos (LC50 = 25 µg L-1). No toxicity was observed for Raphidocelis subcapitata, Ceriodaphnia dubia, or Parhyale hawaiensis. Additional biochemistry/molecular studies are needed to elucidate the toxic/mutagenic pathways of emodin in aquatic organisms. The PNEC value for emodin was 0.025 µg L-1. In addition to mutagenicity in the Salmonella/microsome assay, emodin was mutagenic in the micronucleus assay in the amphipod P. hawaiensis. Among the anthraquinone dyes tested to date, natural or synthetic, emodin was the most toxic to aquatic species.

Anthraquinone biocolourant dermocybin is metabolized whereas dermorubin is not in in vitro liver fractions and recombinant metabolic enzymes.

Fungal anthraquinones dermocybin and dermorubin are attractive alternatives for synthetic dyes but their metabolism is largely unknown. We conducted a qualitative in vitro study to identify their metabolism using human liver microsomes and cytosol, as well as recombinant human cytochrome P450 (CYP), UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) enzymes. Additionally, liver microsomal and cytosolic fractions from rat, mouse and pig were used. Following incubations of the biocolourants with the enzymes in the presence of nicotinamide adenine dinucleotide phosphate, UDP-glucuronic acid, 3'-phosphoadenosine-5'-phosphosulfate (PAPS) or S-adenosyl methionine (SAM) to enable CYP oxidation, glucuronidation, sulfonation or methylation, we observed several oxidation and conjugation metabolites for dermocybin but none for dermorubin. Human CYP1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4 and 3A7 catalysed dermocybin oxidation. The formation of dermocybin glucuronides was catalysed by human UGT1A1, 1A3, 1A7, 1A8, 1A9, 1A10 and 2B15. Human SULT1B1, 1C2 and 2A1 sulfonated dermocybin. Dermocybin oxidation was faster than conjugation in human liver microsomes. Species differences were seen in dermocybin glucuronidation between human, rat, mouse and pig. In conclusion, many CYP and conjugation enzymes metabolized dermocybin, whereas dermorubin was not metabolized in human liver fractions in vitro. The results indicate that dermocybin would be metabolized in humans in vivo.

Is natural better? An ecotoxicity study of anthraquinone dyes.

The concept of sustainability has gained prominence in recent years, enhancing the need to develop products that are less harmful to the environment. Dyes are used by various industrial sectors and have a lot of market value; they are used on a large scale mainly by the textile industry that uses large volumes of water and is one of the main contributors to the contamination of water bodies. Some natural compounds, especially anthraquinones are re-emerging as possible alternatives to synthetic dyes, some of which are known for their toxic and/or mutagenic effects. The BioColour project (https://biocolour.fi/) which is interested in promoting the development of new alternative molecules to synthetic dyes, provided us highly purified anthraquinone dyes dermocybin and dermorubin (>98% purity) extracted from a specie of fungus Cortinarius sanguineus. Dyes were tested for their acute and chronic toxicity using different aquatic organisms. Dermorubin was not toxic to any of the organisms tested for the highest test concentration of 1 mg L-1 and it was the most promising dye. Dermocybin was toxic to Daphnia similis (EC50 = 0.51 mg L-1), Ceriodaphnia dubia (IC10 = 0.13 mg L-1) and Danio rerio embryos (extrapolated LC50 = 2.44 mg L-1). A safety limit, i.e, predicted no-effect concentration (PNEC) of 0.0026 mg L-1 was derived based on the toxicity of dermocybin. The PNEC value can be used to provide hazard information for future application in commercial dyeing processes. Then, we compared the toxicity of dermocybin and dermorubin with ecotoxicity data available in the literature on other anthraquinone dyes of natural and synthetic origin. Some natural dyes can be as toxic as synthetic ones, or more toxic when chronic effects are considered. Despite natural dyes being used since centuries past, there are few ecotoxicological studies available. This study is designed to help develop a more comprehensive understanding of their toxicological properties.

In Situ Adsorption of Red Onion (Allium cepa) Natural Dye on Cellulose Model Films and Fabrics Exploiting Chitosan as a Natural Mordant.

Synthetic dyes and chemicals create an enormous impact on environmental pollution both in textile manufacturing and after the product's lifetime. Biobased plant-derived colorants and mordants have great potential for the development of more sustainable textile dyeing processes. Colorants isolated from biomass residues are renewable, biodegradable, and usually less harmful than their synthetic counterparts. Interestingly, they may also bring additional functions to the materials. However, the extraction and purification of the biocolorants from biomass as well as their dyeing efficiency and color fastness properties require a more thorough examination. Here, we extracted red onion (Allium cepa) skins to obtain polyphenolic flavonoids and anthocyanins as biocolorants, characterized the chemical composition of the mixture, and used a quartz crystal microbalance and thin films of cellulose nanofibrils to study the adsorption kinetics of dyes onto cellulose substrates in situ. The effect of different mordants on the adsorption behavior was also investigated. Comparison of these results with conventional dyeing experiments of textiles enabled us to determine the interaction mechanism of the dyes with substrates and mordants. Chitosan showed high potential as a biobased mordant based both on its ability to facilitate fast adsorption of polyphenols to cellulose and its ability to retain the purple color of the red onion dye (ROD) in comparison to the metal mordants FeSO4 and alum. The ROD also showed excellent UV-shielding efficiency at low concentrations, suggesting that biocolorants, due to their more complex composition compared to synthetic ones, can have multiple actions in addition to providing aesthetics.

Waterless Dyeing and In Vitro Toxicological Properties of Biocolorants from Cortinarius sanguineus.

As a part of an ongoing interest in identifying environmentally friendly alternatives to synthetic dyes and in using liquid CO2 as a waterless medium for applying the resulting colorants to textiles, our attention turned to yellow-to-red biocolorants produced by Cortinarius sanguineus fungus. The three principal target anthraquinone colorants (emodin, dermocybin, and dermorubin) were isolated from the fungal bodies using a liquid-liquid separation method and characterized using 700 MHz NMR and high-resolution mass spectral analyses. Following structure confirmations, the three colorants were examined for dyeing synthetic polyester (PET) textile fibers in supercritical CO2. We found that all three biocolorants were suitable for dyeing PET fibers using this technology, and our attention then turned to determining their toxicological properties. As emodin has shown mutagenic potential in previous studies, we concentrated our present toxicity studies on dermocybin and dermorubin. Both colorants were non-mutagenic, presented low cellular toxicity, and did not induce skin sensitization. Taken together, our results indicate that dermocybin and dermorubin possess the technical and toxicological properties needed for consideration as synthetic dye alternatives under conditions that are free of wastewater production.

Effect of Hybrid Type and Harvesting Season on Phytochemistry and Antibacterial Activity of Extracted Metabolites from Salix Bark.

Hundreds of different fast-growing Salix hybrids have been developed mainly for energy crops. In this paper, we studied water extracts from the bark of 15 willow hybrids and species as potential antimicrobial additives. Treatment of ground bark in water under mild conditions extracted 12-25% of the dry material. Preparative high-performance liquid chromatography is proven here as a fast and highly efficient tool in the small-scale recovery of raffinose from Salix bark crude extracts for structural elucidation. Less than half of the dissolved material was assigned by chromatographic (gas chromatography and liquid chromatography) and spectroscopic (mass spectrometry and nuclear magnetic resonance spectroscopy) techniques for low-molecular-weight compounds, including mono- and oligosaccharides (sucrose, raffinose, and stachyose) and aromatic phytochemicals (triandrin, catechin, salicin, and picein). The composition of the extracts varied greatly depending on the hybrid or species and the harvesting season. This information generated new scientific knowledge on the variation in the content and composition of the extracts between Salix hybrids and harvesting season depending on the desired molecule. The extracts showed high antibacterial activity on Staphylococcus aureus with a minimal inhibitory concentration (MIC) of 0.6-0.8 mg/mL; however, no inhibition was observed against Escherichia coli, Enterococcus faecalis, and Salmonella typhimurium. MIC of triandrin (i.e., 1.25 mg/mL) is reported for the first time. Although antibacterial triandrin and (+)-catechin were present in extracts, clear correlation between the antibacterial effect and the chemical composition was not established, which indicates that antibacterial activity of the extracts mainly originates from some not yet elucidated substances. Aquatic toxicity and mutagenicity assessments showed the safe usage of Salix water extracts as possible antibacterial additives.

Examining Safety of Biocolourants from Fungal and Plant Sources-Examples from Cortinarius and Tapinella, Salix and Tanacetum spp. and Dyed Woollen Fabrics.

Biocolourants have been investigated as alternatives to synthetic dyes. However, natural origin per se is not a label of harmlessness and research is needed to obtain safe dyes. We studied the cytotoxicity of the extracts from fungal (Cortinarius semisanguineus, Tapinella atrotomentosa) and plant (Tanacetum vulgare, Salix phylicifolia) sources and the woollen fabrics dyed with the extracts. Cytotoxicity in vitro using hepa-1 mouse hepatoma cells for 24 h and 72 h exposure was observed as the highest tolerated dose. All biocolourants produced intensive colour on fabrics with fastness properties from moderate to good. The Salix and Cortinarius samples did not show any cytotoxic effects, whereas the Tanacetum and Tapinella samples had slightly higher test values but were not interpreted as being significantly toxic. Higher than zero values of the undyed fabrics showed the importance of examining their toxicity as well. It was found that the cytotoxicity of the samples dyed with the biocolourants did not differ significantly from the undyed wool fabric. The concentrations of dyes used in the assays were very low, imitating the dose of the user. In addition to colouring properties, natural dyes may have pharmaceutical and antibacterial properties which would enhance the interest in using them in products for added value.