Design and formulation of saponin-based, mustard oil-derived, extra stable oil-in-water emulsion: exploration of its antimicrobial activity

Abstract

Saponin-stabilized, mustard oil–based bioactive oil-in-water (O/W) emulsions were prepared as bioemulsifiers that remained in emulsion form for up to 24 h. After standing for 24 h, the emulsions transformed into an emulsion-gel form and maintained their stability for up to 90 d. These emulsion-gel sets show excellent antibacterial (against Pseudomonas aeruginosa) and antifungal (against Candida albicans) activity. Several analytical methods, including rheology, optical microscopy, and FTIR spectroscopy, were performed to characterize the synthesized O/W emulsion-gels and their subsequent stability. The influence of saponin was further investigated, and it was found that upon increasing the concentration of saponin, the droplet size decreased. Moreover, the formulated emulsion gel showed excellent temperature sensitivity and remained stable up to 65 °C. The emulsion gel successfully underwent 25 consecutive cycles of emulsification and de-emulsification, demonstrating its ability for reversible phase switching. Because of its long-term stability (90 d), thermosensitivity, and excellent antibacterial and antifungal effects, these emulsion-gel sets are ideal for broad applications in biomedical fields.