Phytochemical Screening and Physicochemical Properties of Oil Extract of Usnea barbata L. F.H.Wigg from Călimani Mountains, Romania

Green cosmetics are primarily based on plant-derived ingredients and use sustainable biotechnological tools for their preparation. The present research aimed to investigate the Usnea barbata (U. barbata) extract in Jojoba oil (JO) enriched with 5% Peppermint oil (PEO) and 10% Vitamin E, as a potential natural product for skin applications. The U. barbata oil extract (UBPJO) was obtained through cold maceration. Phytochemical screening was performed using Gas Chromatography/Mass Spectrometry (GC-MS), Folin–Ciocalteu method, and Graphite-Furnace Atomic Absorption Spectrophotometry (GFAAS). Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Force Microscopy (AFM) were used to evaluate the physicochemical properties. Then, rheological characteristics and oxidation stability (measured as the time to reach the oxidation starting point, induction period (IP)) of both oil samples (UBPJO and oil mixture alone (PJO) were investigated. Total phenolic content (TPC) in UBPJO was 2.5 times higher than in PJO (p < 0.05), while heavy metal levels (As and Pb) were slightly higher (p > 0.05). UBPJO has higher shear stress, viscosity, and spreadability than PJO, but the differences are not significant (p > 0.05). Finally, IP measurements indicated appreciable oxidative stability (UBPJO vs. PJO: 153.02 h vs. 137.35 h, p > 0.05). The phytochemical composition and physicochemical properties support the inclusion of UBPJO in various skincare formulations.