Efficient Encapsulation of Citral in Fast-Dissolving Polymer-Free Electrospun Nanofibers of Cyclodextrin Inclusion Complexes: High Thermal Stability, Longer Shelf-Life, and Enhanced Water Solubility of Citral.

Zeynep Aytac,Tamer Uyar,Zehra Yildiz,Asli Celebioglu

doi:10.3390/nano8100793

Abstract

Here, we report a facile production of citral/cyclodextrin (CD) inclusion complex (IC) nanofibers (NFs) from three types of CDs (hydroxypropyl-beta-cyclodextrin (HPβCD), hydroxypropyl-gamma-cyclodextrin (HPγCD), and methylated-beta-cyclodextrin (MβCD)) by an electrospinning technique without the need of any polymeric carrier matrix. Self-standing nanofibrous webs of citral/CD-IC nanofibers (citral/CD-IC-NF) with uniform fiber morphology have been successfully electrospun from aqueous solutions of citral/CD-IC. Thanks to the inclusion complex formed with CDs, the efficient preservation of citral (up to ~80%) in citral/CD-IC-NFs was observed. In addition, the citral/CD-IC-NFs have shown ~50% preservation of citral for 15 days at room temperature even though citral has a highly volatile nature. The enhanced thermal stability of citral (~100–300°C) in citral/CD-IC-NFs compared to pure citral (~50–165°C) has been observed. Moreover, citral/CD-IC-NFs tended to disintegrate in water very quickly. To summarize, citral was efficiently encapsulated in citral/CD-IC-NFs, and these citral/CD-IC-NFs have been shown to be fast dissolving. In citral/CD-IC-NFs, citral/CD-ICs have enhanced water solubility of citral along with high-temperature stability and a longer shelf-life.

Highlights

Citral (3,7-dimethyl-2,6-octadienal) is a flavor/fragrance molecule found in lemongrass oil that possesses a lemon-like odor and a bittersweet taste (Figure 1)
The linear increment in the solubility of citral with increasing concentrations of CDs regardless of the CD type in phase solubility diagrams of citral/CD systems indicate that the diagrams are linear (AL ) type, which demonstrates that the complexes formed in a 1:1 molar ratio (Figure 2) [27]
Citral has a volatile nature, our results showed that the release of citral from citral/CD-inclusion complex (IC)-NF during the storage at room temperature was minimal

Summary

Introduction

Citral (3,7-dimethyl-2,6-octadienal) is a flavor/fragrance molecule found in lemongrass oil that possesses a lemon-like odor and a bittersweet taste (Figure 1). Citral is composed of two geometric isomers, geranial and neral, which have an intense lemon odor and a sweet taste, respectively. Citral has low aqueous solubility and is unstable against heat, air, and light [1]. Cyclodextrins (CDs) (Figure 1) hold exceptional complexation capability due to the relatively hydrophobic cavity of the interior of these supramolecular structures and offer an excellent feature to encapsulate a variety of compounds that have appropriate polarity and dimensions that fit into the CD cavity. Similar to other encapsulating methods, the inclusion complexation with CDs provides many advantages to the guest molecules, including enhanced water solubility, higher thermal stability, a longer shelf-life, etc. There are different native CDs and chemically modified CDs (Figure 1a) available on the market

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