Ultrasound triggered process optimization of Etlingera linguiformis (Roxb.) R.M.Sm. nanoemulsion: Its stability, cytotoxicity and antibacterial activity

Periodontal infections and dental caries are leading causes of tooth loss, impacting overall health and quality of life. Conventional treatments involve antibiotics, antiamoebic drugs, and quaternary ammonium compounds, their prolonged use can cause resistance and toxicity. In this study, E. linguiformis essential oil (ELEO) was evaluated for chemical composition, and its nanoemulsion (ELEON) with good stability was characterized for ELEON properties, prepared using ultrasonication, and assessed for their antibacterial efficacy. The results showed that ELEO is dominated by estragole as the major compound, with the 60-minute sonicated sample exhibiting the best stability and uniform droplet size (220.03 d.nm) distribution. Prolonged ultrasonication led to an increase in particle size, highlighting the importance of optimal processing. Antibacterial analysis revealed that ELEON exhibited higher activity than ELEO against S. mutans and S. aureus, attributed to its smaller droplet size and enhanced penetration into microbial cells. Transmission Electron Microscope (TEM) showed the droplet diameter comparable to the particle size measured in Dynamic light scattering (DLS). Scanning Electron Microscopy (SEM) revealed significant morphological changes and membrane disruption in bacteria treated with ELEO and ELEON, leading to cell death. The cytotoxicity of ELEO and ELEON from E. linguiformis rhizomes was evaluated on L929 fibroblast cell lines using the MTT assay, showing no significant reduction in cell viability across tested concentrations. ELEON enhances essential oil stability and antimicrobial efficacy, demonstrating thepotential for pharmaceutical applications and antibiotic resistance management.