NaDES-Based Extracts by Microwave Activation from Laurus nobilis L. Leaves: Sustainable Multifunctional Ingredients for Potential Cosmetic and Pharmaceutical Applications

Laurus nobilis L. is a widely cultivated plant, used for ornamental purposes, as a high-value spice crop, and in the flavor and fragrance industry. In natural medicine, it is well-known for its many beneficial properties (due to a broad spectrum of biologically active compounds) and used for the treatment of different disorders. In this study, natural deep eutectic solvents (NaDESs), coupled with microwave activation, were studied and applied for a green extraction of L. nobilis leaves. The main objective was to obtain a sustainable and multifunctional cosmetic and pharmaceutical ingredient (the NaDES-based extract itself), exploiting both the intrinsic cosmetic functionalities of NaDES components and the biological properties of laurel bioactive compounds. The most promising candidate was obtained from a eutectic system containing betaine, glycerol, and lactic acid. The evaluation of this NaDES-based complex reveals a considerable number of phenolic compounds (around 11.57 mg of gallic acid equivalents for a gram of fresh leaves) and a notable antioxidant activity (80.1% with respect to Trolox), with values quite constant over a period of six months. The complex exhibits effective antimicrobial activity against different Gram-positive (S. aureus and S. epidermidis) and Gram-negative (E. coli and P. aeruginosa) bacterial strains, with concentrations ranging from 3.8 to 7.5 mg/mL. Furthermore, the extract presents a pleasant fragrance, attributable to the selective extraction of different volatile aromatic compounds, as confirmed by GC-MS analysis.