Anti-inflammatory, antioxidant, and antibacterial activity of tea saponin-based Zanthoxylum bungeanum essential oil nanoemulsions against bovine mastitis pathogens

To enhance the applicability of Zanthoxylum bungeanum essential oil (ZEO) from Wudu, China, a tea saponin (TS)-stabilized nanoemulsion (ZEO-NE) was developed. Its composition was analyzed, and the physical properties, stability, and bioactivities were systematically evaluated. GC-MS analysis identified linalool (24.833 %), linalyl acetate (16.076 %), and d-limonene (14.019 %) as the principal constituents. An oil-in-water ZEO-NE was prepared using the natural surfactant tea saponin (TS) as an emulsifier via ultrasonication. The average particle size, zeta potential, and polydispersity index of ZEO-NE were 188.49 ± 6.15 nm, −26.02 ± 0.47 mV, and 0.17 ± 0.04, respectively. The physical properties and biological activity of ZEO-NE were evaluated. ZEO-NE behaved as a non-Newtonian fluid and demonstrated stability over 30 days of storage, within a temperature range of 4–50°C, and under centrifugation at 2000–6000 rpm. Compared to free ZEO, ZEO-NE demonstrated improved scavenging capacities against DPPH, ABTS, and hydroxyl radicals, along with enhanced antibacterial activity against Escherichia coli, Staphylococcus aureus, and S. dysgalactiae. The antibacterial mechanism involved the disruption of bacterial cell walls and membranes. Furthermore, ZEO-NE provided superior protection to bovine mammary epithelial cells against bacterial-induced damage and effectively downregulated the expression of the pro-inflammatory cytokines TNF-α and IL-1β in these cells. These findings demonstrate that nanoencapsulation of ZEO using TS enhances its antioxidant, antibacterial, and anti-inflammatory activities. Consequently, ZEO-NE shows promise as a natural antioxidant for food preservation and holds potential therapeutic value for the treatment of bovine mastitis.