Usnea barbata Extract in Karanja Oil—An Innovative Combination with Antioxidant, Antimicrobial, and Sunscreen Properties, with Potential Applications in Skincare

Plant extracts in vegetable oils are foundational and eco-responsible for skin care, act-ing as potent antimicrobials, antioxidants, photoprotectants, and emollients. The pre-sent research aims to conduct a comprehensive investigation of Usnea barbata extract in Karanja oil (KO). The lichen extract (UBKO) was obtained through cold maceration. Phytochemical screening was performed using the Folin-Ciocalteu method and Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS). Physicochemical properties were evaluated by Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR). The rheological characteristics and oxidative resistance of both oil samples, with and without U. barbata (UBKO and KO), were investigated. The bioactive potential of UBKO was assessed by evaluating antioxidant properties, sunscreen efficacy, and antibacterial and antifungal activity. UBKO had a slightly lower density (0.827 vs. 0.955) and pH (4.22 vs. 4.86) than KO, and a slightly higher oxidative resistance, quantified as the induction period (IP) value (6.45 vs. 6.00). The total phenolic content was significantly greater in UBKO than in KO (567.16 ± 14.96 vs. 433.26 ± 22.96 mg GAE/mL, p < 0.05). The antibacterial effect against S. aureus was higher for UBKO than KO (25 ± 0.00 vs. 31.25 ± 18.75 mg/mL, p < 0.05), while the in-hibitory activity of UBKO against C. albicans was considerably higher than that of KO (6.75 ± 0.00 vs. 37.50 ± 12.50 mg/mL, p < 0.05). Finally, our results showed that UBKO had an appreciable sun-protective factor (SPF) slightly higher than KO (30.9 vs. 29.8). Therefore, our study suggests that U. barbata extract in Karanja oil could be used to develop pharmaceutical formulations with antimicrobial and photoprotective effects, with potential applications for skincare.