Optimization of sustainable processes for the development of semi-solid microemulsions containing plant active substances of Salvia rosmarinus Spenn

Abstract

Objectives: This study presents a sustainable extraction process for obtaining plant active substances (PAS) from the leaves of Salvia rosmarinus Spenn. (rosemary) and semi-solid microemulsions (SSME) at the same time. The extraction method uses a sustainable solvent system of surfactants, co-surfactants, and water, yielding high PAS miscibility. Methods: The method was developed using pseudo-ternary phase diagrams, particle size determination and ultrasound-assisted extraction. Optimization was performed via response surface methodology, assessing antioxidant capacity, total phenols, terpenoids, and flavonoids for efficiency evaluation. Results: Optimal extraction conditions, identified using response surface methodology, which produced SSME with high antioxidant capacity (0.04 to 0.150 mmol/ml) and significant polyphenolic content (0.055 to 0.219 mg of gallic acid/ml). Additionally, the resulting formulations showed a total terpenoid content of 0.04 to 0.150 mmol/ml and a total flavonoid content of 5.4 to 10.5 mg/ml mg quercetin equivalent/ml. The droplet size and polydispersity index values of the optimized extracts were evaluated, yielding mean droplet sizes below 250 nm, indicating the presence of microemulsions. By means of UPLC-ESI-MS/MS the primary PAS were identified, validating the effectiveness of the extraction process in isolating of bioactive compounds with therapeutic potential. Conclusions: This eco-friendly method not only aligns with green chemistry principles but also supports the development of PAS-rich SSME as candidates for dermal therapies.