Potential of supercritical fluid myrtle extracts as an active ingredient and co-preservative for cosmetic and topical pharmaceutical applications

This study investigated the applications of a myrtle extract obtained by supercritical fluid extraction (SFE), a technique considered environmentally friendly, as a possible antimicrobial ingredient in cosmetic and pharmaceutical formulations. The supercritical fluid extract was obtained at 230 bar and 45 °C, for 2 h, with a flow of CO₂ of 0.3 kg h⁻¹. A cosolvent (ethanol) was also used, with a flow 0.09 kg h⁻¹. The extracts thus obtained were tested against seven Gram-positive bacteria and one yeast using the well diffusion and the broth dilution techniques. The results showed that the myrtle extract exhibits good antibacterial activity against all the bacteria strains studied and is superior to most of those obtained by conventional extraction methods. Antifungal activity was also present but at a lesser extent. Cell viability studies were carried out by exposing HaCat cells to a range of extract concentrations, from 0.1 μg/mL up to 60 μg/mL for 24 h, using the MTT assay. The Salmonella mutagenicity assay was applied to evaluate the mutagenicity and antimutagenicity of the extract. The results obtained suggest that the myrtle extract obtained using a green solvent, supercritical CO₂, is safe and could reduce the genotoxic damage induced by reactive oxygen species (ROSs).