Untangling the bioactive properties of therapeutic deep eutectic solvents based on natural terpenes

Treatment of microbial-related infections remains a clinical challenge that has been slowly aggravating over recent years, due to the dissemination of resistance against currently applied treatment protocols. In this current scenario, the design of novel treatment approaches is of great importance, being a prominent focus of the scientific community. In recent years deep eutectic systems (DES) have gained the attention of the scientific community due to their remarkable physicochemical and biological properties, versatility, and compliance with the green chemistry metrics. In this work, DES containing a monoterpenoid (thymol (THY) and menthol (ME)) in combination with ibuprofen (IBU) were formulated and characterized via thermal analyses and NMR spectroscopy. The biological activity of the most promising formulations was then explored, with focus on its antimicrobial and anticancer activity. Both ME and THY-based formulations presented relevant antibacterial activity against the panel of microorganisms tested. Among the THY-based formulation tested, THY:IBU 3:1 molar ratio, showed the highest antibacterial activity, affecting all tested microorganisms, while ME:IBU 3:1 molar ratio was only effective against Gram-positive bacteria and Candida albicans. Furthermore, both ME and THY-based formulations revealed cytotoxic effect towards the cancer cell model used (HT29), where ME:IBU 3:1 stood out as the most selective towards cancer cells without compromising normal cells viability. Overall, the results obtained highlight the potential use of terpene-based THEDES formulations that, due to their enhanced thermal properties, may represent a versatile alternative in several biomedical applications where an effective antimicrobial or anticancer therapeutic action remains a challenge.