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A commonly used preservative that could turn harmful when exposed to UV light.

Scientists from CSIR-Indian Institute of Toxicology Research (CSIR-IITR) and Babu Banarasi Das University in Lucknow, Uttar Pradesh have been studying the properties and behaviour Methylparaben, a commonly used preservative, under various circumstances. Their study reveals that, when exposed to Ultraviolet (UV) light, the molecule, not just loses it ability to effectively perform as a preservative, but also could damage human skin cells.

Methylparaben (MP) is a commonly used preservative in pharmaceuticals, food and cosmetic products, known for its antifungal properties. Although considered as safe, easily biodegradable, and validated by US Food and Drug Administration as ‘generally recognized as safe’ (GRAS), there have been concerns over the safety of concentration of the molecule, especially when used in cosmetic and food products. One major concern has been its behaviour under ambient UV radiation, which is not very well understood.

In their new study, the scientists wanted to learn about the effects of UV light on MP as well as the effects of MP exposed to UV light, called photosensitized MP, on human cells.

The study has revealed that MP not just loses its preservative properties but also turns harmful to human cells, when exposed to ambient UVB light. MP that was exposed to ambient UVB light, showed a 40% reduction in its antimicrobial activity, when exposed to a E-Coli culture. Further, the study showed that photosensitized MP significantly increased Lipid Peroxidation, which leads to the formation of compounds like free radicals which can reduce the shelf life of a product. It also increased the generation of reactive oxygen species, a type of reactive chemical containing oxygen which when produced in excess could lead to oxidative stress causing damage to proteins, lipids and even DNA in the body.  

Apoptosis or programmed cell death is another phenomenon that was affected by the photosensitized MPs. It was found to do this by affecting enzymes called caspases, which plays an important role in apoptosis. Photosensitized MPs also disrupted mitochondrial membrane integrity and Endoplasmic Reticulum mediated stress, further affecting apoptosis.

The scientists concluded saying “Results indicate that photosensitive MP leads to oxidative stress mediated DNA damage and apoptosis through mitochondria and ER. MP causes deleterious effects and its long term exposure to human skin may promote skin diseases”

With the study providing concrete evidence for the harmful effects of MP, perhaps it is time to look for other preservatives that could replace the molecule, one that does not change when shone with light.