The safety of dyes obtained from the bloodred webcap fungus can vary, according to a new doctoral dissertation exploring their toxicity. Completed at the University of Eastern Finland, the study found that red dermorubin seemed safe in cellular studies, whereas yellow emodin caused mutations in a commonly used bacterial mutation test and oxidative stress in human cells.
The bloodred webcap (Cortinarius sanguineus) is a traditional textile dyeing mushroom that produces up to 15 different anthraquinone dyes.
“Synthetic dyes that are currently used, as well as their production, are a major environmental pollutant. There is a need for sustainably produced, biodegradable dyes for textiles and packaging, and the bloodred webcap is a potential source for those,” Doctoral Researcher Johanna Yli-Öyrä of the University of Eastern Finland notes and continues:
“However, natural origin is not a safety guarantee, and it is important to study the safety aspects of dyes obtained from the bloodred webcap before large-scale production and use.”
The study explored the toxicity of the most common dyes obtained from the bloodred webcap – emodin, dermocybin and dermorubin – as well as a mixture extract of the mushroom. The study also analysed the metabolism of the dyes, or how they are chemically transformed in the body, as sometimes the toxicity of a substance requires metabolic activation.
It was found that emodin, the most commonly present dye in the bloodred webcap, causes mutations in a bacterial mutation test, and oxidative stress in human cells. It can also cause skin sensitisation – in other words, allergies. Orange dermocybin caused some oxidative stress in human cells but other harmful effects were not detected.
“However, we found that dermocybin is metabolised into several products whose activity is not known. Dermocybin seems to be a good dye option, but further studies are needed to be sure,” Yli-Öyrä says.
“Red dermorubin, on the other hand, seems to be a safe and good dye – it did not cause cellular toxicity, and it does not get chemically transformed in the body.”
According to Yli-Öyrä, it can also be deduced from the results that, in terms of safety assessment, anthraquinones cannot be handled as a single group.
“Even though their chemical structure is similar, their toxicity varies from compound to compound.”
Human immune and liver cell lines were used in the study. Skin sensitisation potential was assessed using the KeratinoSens assay, which has been developed to replace sensitisation-related animal tests. Metabolism was studied using several metabolic enzymes from human and different animal species.
The doctoral dissertation was completed as part of the BioColour research consortium that consists of a multidisciplinary group of researchers who examine new opportunities related to natural dyes. The results can advise further development of natural dye production.