Monarda essential oils as natural cosmetic preservative systems

Abstract

The aim of the study was (1) to compare the antimicrobial activity of essential oils (EOs) obtained from leaves and inflorescences of Monarda media, Monarda didyma and Monarda citriodora found in different phenological stages of development, (2) to examine the inhibition of microbial growth by Monarda EOs in O/W emulsions. Thymol, p-cymene and carvacrol were the main constituents in Monarda EOs. The strongest antimicrobial activity were 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 tested bacteria and fungi, while M. didyma and M. citriodora EOs does not meet criterion for Gram-negative bacteria. M. media EO can be an effective candidate for a natural cosmetic preservatives and finally create self-preserving system in O/W emulsion, while M. didyma and M. citriodora EOs can only reduce concentration of synthetic preservatives in O/W emulsions.