D-optimal design-assisted Elaeis guineensis leaves extract in olive oil-sunflower seed nanoemulsions: development, characterization, and physical stability

Abstract

A three-factor D-optimal mixture design was used to prepare the Elaeis guineensis leaves extract (EgLE) in olive oil-sunflower seed nanoemulsions. The assessed independent variables were the components of an oil-based nanoemulsion that included oil (8–12%, w/w), Span 80:Brij L23 (28–30%, w/w) and aqueous (56–60% w/w) with mean droplet size (MDS) and polydispersity index (PDI) as the responses. Analysis of variance revealed that both responses fitted a quadratic polynomial model and a residual standard error of <5% indicated good agreement between the experimental and predicted values. Optimal formulation with the lowest MDS and PDI was established to be 10% (w/w) oil, 29% (w/w) Span 80:Brij L23 and aqueous at 58% (w/w). Atomic force micrographs showed the MDS of an optimized EgLE w/o nanoemulsion being <200 nm and was kinetically stable (zeta potential: −30.0 ± 0.7 mV). The system showed satisfactory conductivity (0.70 ± 0.02 µS cm⁻¹) and pH (5.6 ± 0.3), alongside resistance to phase separation under centrifugation and freeze-thaw cycles. The nanoemulsion also exhibited shear thinning and pseudoplastic properties, implying good stability against destabilization by coalescence. It can be construed that the developed EgLE nanoemulsion showed potential as a natural-based personal care product. This is the first report on the preparation of EgLE as bioactive ingredients in a w/o nanoemulsion for topical application.

Highlights

R₂ values from ANOVA models of MDS and PDI are 0.9263 and 0.9095, respectively Optimal EgLE formulation was 10% oil, 29% surfactant and 58% water Optimal EgLE formulation showed MDS and PDI of 188.4 nm and 0.22, respectively Optimal EgLE nanoemulsion gave an acceptable pH of 5.6 EgLE nanoemulsion was stable with storage for 90 days at 4 °C, 25 °C and 37 °C

Graphical Abstract

Keywords:

• D-optimal mixture design
• Elaeis guineensis leaves extract
• nanoemulsion
• mean droplet size
• polydispersity index

Additional information

Funding

This work was supported by the Fundamental Research Grant Scheme (R.J130000.7854.5F013) from the Ministry of Higher Education. The author is grateful to Universiti Teknologi Malaysia for funding her Zamalah Scholarship.