Individual stereoisomers of verbenol and verbenone express bioactive features

Abstract

Naturally occurring terpene core compounds have been used extensively in both pharmaceutical and cosmetic industry. However, since chirality of these compounds has profound influence on the level of their bioactivity, the aim of the present study was to assess broad spectrum activities of four possible stereoisomers of monoterpene alcohol verbenol and both enantiomers of monoterpene ketone verbenone. Antimicrobial activity was evaluated against different bacterial and fungal strains of clinical relevance. Tested compounds exhibited antibacterial activity within MICs range of 0.6–2.5 mg mL−1, antifungal activity within MICs range of 0.08–0.6 mg mL−1, and anticandidal activity with MICs 0.3–1.2 mg mL−1. While there was no difference in antibacterial activity between the enantiomers of verbenone, this was not the case with tested verbenol enantiomers. Furthermore, the compounds expressed no cytotoxicity to human keratinocyte cell line HaCaT at the tested concentrations. Interestingly, compounds contributed to the downregulation of interleukin IL-6 levels in HaCaT cells exposed to bacterial agent Staphylococcus lugdunensis. According to our knowledge, this study is the first that comparatively describes biological activities of stereoisomers of verbenol and enantiomers of verbenone. Current findings highlighted the importance of stereochemical purity of monoterpenoids in relation to their unique biological features.