Monarda essential oils as natural cosmetic preservative systems

Abstract

The aim of the study was to compare the antimicrobial activity of essential oils (EOs) obtained from leaves and inflorescences of Monarda media, M. didyma, and M. citriodora found in different phenological stages of development, to examine the inhibition of microbial growth by Monarda EOs in O/W emulsions. Thymol, p-cymene, and carvacrol were the main constituents characterized in Monarda EOs. The strongest antimicrobial activity was obtained from the leaves of Monarda EOs in the flowering phase of the development. M. media EO fulfilled the criterion of the preservative effectiveness test for all evaluated bacteria and fungi, while M. didyma and M. citriodora EOs were not sufficient for Gram-negative bacteria. As an overall result, M. media EO may be an effective candidate as natural cosmetic preservative, and finally create self-preserving system in O/W emulsion, while M. didyma and M. citriodora EOs may only reduce the amount of synthetic preservatives used in O/W emulsions.