Antimicrobial multi-component lipid-based nanoemulsion of Eucalyptus globulus and Mentha piperita as natural preservative

Abstract

Natural preservatives were predominantly developed to eliminate the use of synthetic preservatives for food and agriculture industries. Multi-component nanoemulsions (MCN) with significant antibacterial activity should be proper candidates as natural preservatives. This research aimed to formulate a multi-component phospholipid-based nanoemulsion (PNE) with prolonged shelf-life loaded with a mixture of Eucalyptus globulus and Mentha piperita essential oils (EOs). The effects of different chemical and mechanical conditions (ultrasonication) on the stability of MCN were evaluated. The emulsions were monitored from day 1 to 730, and stable formulae were investigated for around two years. The Zeta potential confirmed the anionic surface charge. Dynamic light scattering and transmission light scattering revealed a droplet size ranging between 93.40 and 100.00 nm. A homogeneous formula was stable for more than 730 days. Ultrasonication treatment and 1% v/v of food-grade castor oil as co-emulsifier were critical in fabricating stable formulae. Minimum inhibitory concentration (MIC) values of 31, 8, and 63 µg/ml were observed against Escherichia coli, Staphylococcus aureus and Salmonella enteritidis, respectively. The results showed a significant reduction in MIC values of 32-, 250-, 15-fold against E. coli, S. aureus and S. enteritidis, respectively, compared to an original mixture of essential oils. The mass transfer followed a case-I transfer (Fick law diffusion) evaluated by Koresmeyer-Peppas kinetic model (R² = 0.88). In conclusion, MCN could be a promising candidate for natural preservatives to be used in the food, agriculture and cosmetic industries.

Graphical Abstract

Keywords:

• Encapsulation
• nanoemulsion
• lecithin
• ultrasonication
• shelf life

Author contributions

Conceptualization: Faezeh Fathi, Samad N. Ebrahimi, M. Beatriz P. P. Oliveira; methodology: Faezeh Fathi, Atefeh Safari, Zeinab Shahsavari; validation: Samad N. Ebrahimi, Peyman Salehi, Javad Hadian; resources: Samad N. Ebrahimi, Javad Hadian, M. Beatriz P. P. Oliveira; writing—original draft preparation: Faezeh Fathi; writing—review and editing: Samad N. Ebrahimi, Javad Hadian, Luís Carlos Matos, Rita C. Alves; supervision: Samad N. Ebrahimi, M. Beatriz P. P. Oliveira.

Acknowledgments

The experiments and supply of the EOs were supported by Vasha Darou Pars Herbal Pharmaceutical Co. and the Research Council of Shahid Beheshti University (Iran). Faezeh Fathi is also grateful to Laboratório Associado para a Química Verde–Tecnologias e Processos Limpos–UIDB/50006/2020 that supports her grant REQUIMTE 2020-20. R. C. Alves thanks to Fundação para a Ciência e a Tecnologia for the CEECIND/01120/2017 contract.

Additional information

Funding

This work was supported by the UIDB/50006/2020 project, funded by FCT/MCTES (Portugal) (through national funds); by the AgriFood XXI R&D&I project (NORTE-01-0145-FEDER-000041) cofinanced by the European Regional Development Fund, through the NORTE 2020 (Programa Operacional Regional do Norte 2014/2020); and by the SYSTEMIC “an integrated approach to the challenge of sustainable food systems: adaptive and mitigatory strategies to address climate change and malnutrition,” Knowledge hub on Nutrition and Food Security.