Nanoemulsion of Silybum marianum Seeds Extract: Evaluation of Stability, Antioxidant and Antibacterial Activity

Silybum marianum seeds extract (Silymarin) application is often limited by its low aqueous solubility. Using a nanoemulsions system is one way to address this issue. This study aimed to prepare and characterize a stable formulation of Silymarin-based nanoemulsion to investigate the synergistic antioxidant and antibacterial activity of Silymarin and lemon essential oil (LEO) as oil phase. Nanoemulsion containing Silymarin (SiLONE) was developed, and its properties were investigated. The nanoemulsion yielded a particle size of 13.1 nm, a zeta-potential of +0.8 mV, and a 98% encapsulation efficiency. It was stable for more than 6 months at 25°C. The half maximal inhibitory concentration (IC50) of antioxidant activity of Silymarin, combined Silymarin-LEO as bulk form (SiLEB) and SiLONE were 165.04 ± 0.07, 146.96 ± 0.11, and 87.70 ± 0.11 µg/mL, respectively. SiLONE exhibited a better performance in Gram-positive strains than Silymarin or LONE (P < 0.001). The combination of Silymarin with LEO significantly increased antioxidant and antibacterial activity compared to each compound alone (P < 0.001). Also, reducing particle size to nano-range increased antioxidant activity (P < 0.001). Consequently, SiLONE is an excellent antioxidant agent with a powerful antibacterial effect on Gram-positive bacterial strains and is recommended for biomedical applications.