Evaluation of the Physicochemical Properties and In Vitro Biological Activities of Milk thistle (Silybum marianum) Seed Oil: Exploring Its Potential Applications in Dermatological and Cosmetic Field

Abstract

This study aimed to evaluate the physicochemical properties and biological activities of Silybum marianum seed oil, while exploring its potential in dermatological and cosmetic applications. The oil was obtained by cold pressing, yielding an extraction rate of 11.52%, with a near-neutral pH of 6.24 and a density of 0.92 g/mL, indicating good skin compatibility and structural stability . The oil also demonstrated a very high ultraviolet protection capacity, with a sun protection factor (SPF) of 135.3. Regarding antioxidant activity assessed by the FRAP assay, the results revealed a highly significant statistical difference between Silybum marianum seed oil and ascorbic acid. The EC₅₀ value of the oil was 0.336 ± 0.006 µg/mL, compared to 0.425 ± 0.004 µg/mL for ascorbic acid. Statistical analysis using the Student’s t-test for two independent samples confirmed that this difference was highly significant (***, P < 0.001), demonstrating the superior reducing power of the oil in iron reduction and free radical scavenging . The oil also exhibited strong inhibitory activity against tyrosinase, with an IC₅₀ value of 16.8%, compared to 45% for the reference compound, highlighting its potential effectiveness in reducing melanin synthesis. In terms of antibacterial activity, the oil showed considerable efficacy, with MIC and MBC values ranging from 40 to 80 mg/mL, depending on the bacterial strains tested. The MBC/MIC ratio of 1 confirmed its bactericidal effect . Furthermore, the oil demonstrated a clear concentration-dependent inhibition of biofilm formation, along with low to moderate dose-dependent cytotoxicity, suggesting an acceptable safety margin . Based on these findings, Silybum marianum seed oil appears to be a promising multifunctional natural source with antioxidant, antibacterial, and skin-lightening properties, making it a potential candidate for pharmaceutical and cosmetic applications.