Free radical scavenging effects of grapefruit essential oil nanoemulsion stabilized with carrageenan and its cytotoxicity assay on HeLa cell line

Grapefruit peel essential oil exhibited antioxidant and antibacterial activities attributed to their phenolic and flavonoid compounds. In this study, nanoemulsion of grapefruit peel essential oil and carrageenan was investigated for their antioxidant properties. The oil in water (o/w) emulsion was formulated with 0.5% and 1.0% (w/v) grapefruit peel essential oil and carrageenan. Carrageenan was utilised as an encapsulating agent to decrease volatility of essential oil and increase its stability. The resulting nanoemulsion was characterised using transmission electron microscopes (TEM), ultraviolet–visible (UV–vis) spectrophotometry and Fourier-transform infrared spectroscopy (FTIR). Nanoemulsion formulated with 0.5% grapefruit peel essential oil exhibited strong radical scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) effects showing the highest half maximal effective concentration value (EC50) at 83.4 ± 1.4 mg l−1 and revealed the highest total phenolic content (80.1 ± 11.8 mg GAE/g) in comparison with 1.0% grapefruit peel essential oil-nanoemulsion and free grapefruit peel essential oil (2.0% w/v). The cytotoxicity of nanoemulsion prepared from grapefruit peel essential oil against HeLa cells also exhibited higher than 90% of cell viability, which was not affected by the formulation of nanoemulsion. The incorporation of grapefruit peel essential oil into nanoemulsion improved its stability while retaining its bioactivity and non-toxicity.