Development and Evaluation of an Antimicrobial Formulation Containing Rosmarinus officinalis

Rosmarinus officinalis belongs to the Lamiaceae family, and its constituents show antioxidant, anti-inflammatory, antidepressant, antinociceptive, and antibacterial properties. The aim of this study was to develop a topical formulation with R. officinalis extract that had antimicrobial and antioxidant activity. Maceration, infusion, Soxhlet, and ultrasound were used to produce rosemary extracts, which were submitted to antioxidant, compound quantification, cell viability, and antimicrobial assays. Infusion and Soxhlet showed better results in the DPPH assay. During compound quantification, infusion showed promising metabolite extraction in phenolic compounds and tannins, although maceration was able to extract more flavonoids. The infusion and ultrasound extracts affected more strains of skin bacteria in the disk diffusion assays. In the minimum inhibitory concentration assay, the infusion extract showed results against S. aureus, S. oralis, and P. aeruginosa, while ultrasound showed effects against those three bacteria and E. coli. The infusion extract was chosen to be incorporated into a green emulsion. The infusion extract promoted lower spreadability and appropriated the texture, and the blank formulation showed high levels of acceptance among the volunteers. According to the results, the rosemary extract showed promising antioxidant and antimicrobial activity, and the developed formulations containing this extract were stable for over 90 days and had acceptable characteristics, suggesting its potential use as a phytocosmetic. This paper reports the first attempt to produce an oil-in-water emulsion using only natural excipients and rosemary extract, which is a promising novelty, as similar products cannot be found on the market or in the scientific literature.