Lemon balm (Melissa officinalis) has been used for more than 2000 years as a spice aromatic ingredient in food and as a medicinal plant in traditional medicine, as it has many beneficial effects on well-being and health. In cosmetics, it is used in the form of an extract, as a natural ingredient with antioxidant, anti-inflammatory, antibacterial and regenerative effects. It is most commonly found in creams, lotions, and tonics.
In the thesis, we evaluated the safety of lemon balm extract as a cosmetic ingredient, using the threshold of toxicological concern (TTC) approach, which is based on the classification of compounds into Cramer's toxicity classes, according to their chemical structures. By a thorough literature review, we analyzed the qualitative and quantitative composition of the extract and then calculated selected physicochemical parameters of individual compounds present in the extract using the ChemOffice software. The generated values coupled with the known concentrations of compounds in the extract enabled the calculation of their potential extent of absorption and, in turn, the systemic exposure to individual compounds. We have found that the calculated values of systemic exposure (SED) do not exceed those determined for Cramer’s toxicity classes. For compounds whose concentrations in the extract were not found in literature, we calculated the maximum permissible systemic exposure based on TTC values of Cramer's class into which they were classified and their estimated potential extent of absorption. Finally, we found the no observed adverse effect level (NOAEL) values for some of the compounds in the literature, based on which we calculated their acceptable daily intakes (ADI), which by far superseeded the values obtained by the TTC approach. Based on all calculations, we concluded that substances in lemon balm extract do not pose a risk to users with predictable methods of use. The lemon balm extract is safe for use as a cosmetic ingredient.
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