Elsevier

Industrial Crops and Products

Volume 140, 15 November 2019, 111615
Industrial Crops and Products

Enhancing stability of Eucalyptus citriodora essential oil by solid nanoliposomes encapsulation

https://doi.org/10.1016/j.indcrop.2019.111615Get rights and content

Highlights

  • Eucalyptus citriodora essential oil (ECEO) was successfully encapsulated in solid liposomes.

  • β-cyclodextrin was used as cryoprotectant during freeze-drying process.

  • ECEO solid liposomes exhibit higher stability than liquid liposomes.

Abstract

Eucalyptus citriodora essential oil (ECEO) possesses numerous pharmaceutical properties. However, effective applications of ECEO are limited by their volatile nature and poor stability. For purpose of improving the stability and prolonging the shelf life of ECEO, it was encapsulated in solid nanoliposomes (SLPs) by the thin film dispersion method followed by the freeze-drying process. The optimal concentration of ECEO in liposomes was 4.0 mg/mL, and its particle size was found to be 266.56 nm with PDI of 0.188, the zeta potential of -33.73 mV. The maximum encapsulation efficiency (EE) of ECEO in liposomes was obtained as 22.47%. β-cyclodextrin was used as cryoprotectant during freeze-drying process with the suitable ratio of 6:1 to the lipid. Also, results of FT-IR and QCM confirmed that ECEO was encapsulated in solid liposomes successfully. Meanwhile, the morphological features of ECEO-SLPs were analyzed by AFM. Moreover, the release rate and the storage stability of ECEO-SLPs were also measured, which revealed that ECEO encapsulated in solid liposomes have strong stability and the products of ECEO-SLPs can be extended to relevant industrial applications.

Introduction

Eucalyptus, a medicinal plant belongs to Myrtaceae family, symbolizes an important source of essential oil with potent biological activities including antibacterial, antifungal and antiviral properties (Benchaa et al., 2018). Among various species, Eucalyptus citriodora is one of the most cultivated types due to its high economic value. Eucalyptus citriodora essential oil (ECEO), generally extracted from its leaves and used for ornamental, spices, soap, cosmetics and medicinal purposes (Batish et al., 2008; de Araújo-Filho et al., 2018). Moreover, essential oils including ECEO have also been used as herbicidal, insecticidal, antibacterial, anti-helminthic, anti-tumor, as well as in integrated disease management against plant pathogens and mastitis in animals (Luqman et al., 2008; Cui et al., 2018a, 2019). However, diverse industrial applications of ECEO are restricted due to its volatility, decomposability in the presence of air, light and high temperature (Xiao et al., 2010).

In order to overcome these limitations, many novel encapsulation techniques like lipid nanosystem, microcapsule and electrospinning have been developed to improve its stability (Baldim et al., 2019; Lin et al., 2018a; Sáncheznavarro et al., 2011). Liposomes, which are formed by one or multiple lipids bilayers, have been demonstrated that it is an effective system to encapsulate unstable substance like essential oils and release them at the desired time and place (Cui et al., 2016a). However, phospholipids oxidation, leakage of essential oil and aggregation of particles may be occurred during long-term storage of liposomes. The occurrence of these phenomena is due to the fact that liposomes are water-soluble substances (Immordino et al., 2006). Hence, essential oils encapsulated in liposomes must be converted into solid form along with cryoprotectant.

It has been proved that solid liposomes (SLPs) are a novel-embedding technology and exhibited excellent stability, bioavailability and biocompatibility than aqueous liposomes (Baldim et al., 2019). In practice, SLPs are more convenient for storage and transportation. Moreover, β-cyclodextrin, a kind of oligosaccharide with high glass transition temperature, can be employed to protect liposomal membranes during the process of freeze-drying (Chang et al., 2005).

The present study aimed to prepare optimal solid nanoliposomes encapsulated Eucalyptus citriodora essential oil and estimate its stability. The optimal concentration of ECEO in liposomes and the reasonable ratio of β-cyclodextrin to lipid were ascertained by several qualitative and quantitative indexes. In addition, the release rate of ECEO and the storage stability of ECEO-SLPs were also evaluated in terms of practical and effective utilization in industry.

Section snippets

Materials

Eucalyptus citriodora essential oil (ECEO) was purchased from J.E International (Caussols, France). Soy lecithin and cholesterol were bought from Sigma-Aldrich Chemical Co., Ltd (St. Louis, MO, USA). Anhydrous ethanol, polyvinylpyrrolidone (PVP) and β-cyclodextrin were obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).

Chemical components of ECEO

The chemical components of ECEO were confirmed by GC–MS (Agilent 6890GC/5973NMSD, NYSE: A, USA). A fused silica capillary Agilent Technology HP-5 ms column(30 m

Chemical components of ECEO

Different chemical components of ECEO were recorded from GC–MS analysis and results were shown in Table 1. Citronellal was identified as the major component of ECEO, which was corresponded to 79.19% of the total amount. In addition, citronellol (5.95%), isopulegol (2.63%), 1,8-cineole (1.59%), dihydrocarveol (0.78%), terpineol (0.44%) and terpinolene (0.39%) were also detected.

Characterization of ECEO liposomes

The results of four characteristic indicators of ECEO liposomes with various concentration of ECEO were presented in

Conclusion

The present study performed a successful encapsulation of Eucalyptus citriodora essential oil in solid liposomes at a concentration of 4.0 mg/mL through the thin film dispersion method combined with freeze-drying process. Meanwhile, β-cyclodextrin was employed as cryoprotectant to prevent loss of essential oil during this process. Subsequently, the suitable ratio of β-cyclodextrin to lipid at 6:1 was further determined by the results of SEM, DSC and phospholipid antioxidant ability of

Acknowledgements

This research project was financially supported by Hunan Science and Technology Major Project (Grant no. 2016NK1001-3), Natural Science Foundation of Jiangsu Province (Grant no. BK20170070), Jiangsu Province Foundation for talents of six key industries (Grant no. NY-013 and JNHB-131), Jiangsu University Research Fund (Grant no. 11JDG050) and the 18th batch of Jiangsu University Students' Research Funded Project (Grant no. 18A405).

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