Elsevier

Industrial Crops and Products

Volume 108, 1 December 2017, Pages 128-139
Industrial Crops and Products

Production of Copaiba oleoresin particles from emulsions stabilized with modified starches

https://doi.org/10.1016/j.indcrop.2017.06.027Get rights and content

Highlights

  • The use of ultrasound yielded highly stable emulsions.

  • The obtained particles maintain the amorphous structure present in the biopolymers used.

  • The encapsulation process produced particles with high oxidative stability.

  • The surface of particles obtained by SD was smooth and without breaks.

  • Both polymers demonstrated good encapsulation efficiency.

Abstract

The oleoresin of copaiba has many pharmacological properties, such as anti-inflammatory, antiseptic, and cicatrizing, besides helping to treat skin diseases, among other applications. In order to improve its activity, copaiba oleoresin was encapsulated within polymeric particles through emulsification assisted by ultrasound followed by a drying process. Ultrasound-assisted emulsification led to the formation of kinetically stable emulsions. The emulsions with increased stability and the lowest droplet diameters (80.95 ± 2.1 nm (Hi-Cap 100®) and 71.8 ± 2.9 nm (Snow-Flake® E 6131)) were subjected to freeze-drying and spray-drying to produce dry particles. The particles were characterized in terms of moisture content, particle size distribution, encapsulation efficiency, surface oil, oxidative stability, X-ray diffraction and morphological analysis by FESEM and CLSM. Both drying techniques produced amorphous particles with different sizes and low moisture content. Furthermore, high encapsulation efficiency and high stability against thermal degradation were achieved. The analysis of the particles’ morphology indicated that the nature of the biopolymers used (Hi-Cap 100® and Snow-Flake® E 6131) did not affect their microstructure. However, as expected, the freeze-drying and spray-drying techniques produced particles with different external microstructures. SD particles were spherical, whereas FD particles presented irregular structures similar to sheets.

Introduction

The Brazilian rainforest is known for its exuberance and variety of tropical plants that provide alternative sources of therapeutic agents for the treatment of certain diseases. The copaiba tree (Copaifera sp.) exudes oleoresin, a clear smelly liquid with biological properties widely described in the literature (Veiga Junior et al., 2001). Copaiba oleoresins are mixtures of sesquiterpenes and diterpenes, which composition varied depending on the species (Cascon and Gilbert, 2000, Veiga Junior et al., 2007).

Due to the hydrophobic nature of copaiba oleoresin, its direct application on the skin may cause an unpleasant sensation. Therefore, the development of a topical dosage product may be beneficial. Oil-in-water emulsions (O/W) are widely used in the pharmaceutical industry for this purpose, because they act as carriers, increasing the stability and retention of active compounds (Dias et al., 2014). According to McClements (2004), the main drawback for the industrial application of emulsions is their thermodynamic instability. Many physical-chemical mechanisms contribute to this instability, including density separation, coalescence, and flocculation. Depending on the droplet size, emulsions can be classified into micro- (10–100 nm), mano- (20–200 nm) and macro-emulsions (0.5–100 μm) (Henry et al., 2010). The terms micro-emulsion and nano-emulsion were first described by Schulman and Montagne (1961) and Calvo et al. (1996), respectively. According to McClements (2012), the difference among those terms is the stabilization principle of the emulsion. The kinetically stabilized emulsions are known as nano-emulsions, and those thermodynamically stabilized are called micro-emulsions. The main advantage of a nano-emulsion over a macro-emulsion is the high stability of its droplets against coalescence, phase separation or creaming (Anton et al., 2008).

According to Silva et al. (2015a), there are several methods to produce emulsions, such as high-energy emulsification methods including high-pressure, microfluidization and emulsification assisted by ultrasound. The use of ultrasound presents several advantages: i) it produces more stable emulsions with droplets of smaller size; ii) it requires minimal amounts of surfactant agents; iii) it is easy to operate, control and clean. The droplet size can be controlled through various process parameters, such as oil and emulsifier concentrations, oil/emulsifier ratio, viscosity of the continuous phase and emulsification time (Nakabayashi et al., 2011). The stability of emulsions can be improved by the addition of surfactants or biopolymers, which are often proteins or polysaccharides obtained from natural sources (Dickinson, 2009 Dokić et al., 2012).

Emulsions are widely used in pharmaceutical products for the delivery systems of certain ingredients by oral or topical (skin and eye) use. The main interest in the production of emulsions is to encapsulate an active hydrophilic or lipophilic component within the dispersed phase, thus ensuring its protection against environmental stress and degradation (oxygen, light, enzymes, acidity, etc.), and enabling a controlled release (Bouyer et al., 2012). According to de Paz et al. (2013), formulations based on emulsions have been particularly successful, since the emulsion allows controlling and reducing the particle size, therefore enhancing the encapsulation of particles in a polymeric material.

The drying of emulsions to obtain a particulate powder is frequently carried out through freeze-drying and spray-drying. The physical and chemical properties of the active compound are mandatory to select the drying technique to be applied (Silva et al., 2016). Furthermore, the selected technique will also have effect over the encapsulation efficiency, which is one of the most important quality parameters for encapsulation of bioactive compounds, since it indicates the relative amount of active compound that is protected within the polymeric matrix against adverse conditions that may cause its degradation. Finally, the presence of oil over the particle surface is undesirable, since it not only affects the powder wettability and dispersibility, but also makes the particles readily susceptible to oxidation and rancidity (Jafari et al., 2008).

Therefore, the objective of this work was to encapsulate the copaiba oleoresin within polymer matrices through emulsification assisted by ultrasound followed by freeze-drying (FD) or spray-drying (SD). Highly stable emulsions were obtained and the effects of ultrasonic power and sonication time on their mean droplet diameter were evaluated. Next, the emulsions with the smallest droplets were subjected to FD and SD to obtain dry particles.

Section snippets

Plant material and biopolymers used as emulsifiers

Copaiba (Copaifera officinalis) oleoresin was purchased from Ferquima Industria Trade Ltda, located in Vargem Grande – SP, Brazil. The oleoresin was stored in a hermetic dark-colored bottle at 5 °C until the preparation of the emulsions.

The modified starches Hi-Cap 100® (HC) and Snow-Flake® E 6131 (SF), both derived from maize starch, were the biopolymers used to produce the emulsions. Both were donated by Ingredion Brazil Industrial Ingredients Ltda. (Mogi Guaçu-SP, Brazil). HC (used in the

Effect of formulation

The models generated for the mean diameter of droplets were properly adjusted considering only the significant terms (Eqs. (5) and (6)). The adjusted parameters presented correspond to the encoded model, thus the variables do not assume their real values. The determination coefficients for the droplet mean diameters were 98% and 99% for HC and SF, respectively. The F test was highly significant for both, confirming that the models provide statistical significance and can be used for predictive

Conclusions

This paper addresses the production of copaiba oleoresin particles from emulsions generated by emulsification assisted by ultrasound and stabilized by modified starch. The tested polymers showed similar characteristics, since both derived from corn. However, the emulsions produced with these biopolymers presented different stability characteristics: HC provided more stable emulsions. The emulsion droplet size was significantly influenced by ultrasonic power and sonication time. Spray-drying and

Acknowledgments

The authors wish to thank CAPES for the granting of the scholarship and funding this research project, FAPESP (2015/11932-7 and 2016/13602-7), and CNPq (472523/2013-9) for financial support, the LME/LNNano/CNPEM for the technical support during FESEM analysis, and the National Institute of Science and Technology on Photonics Applied to Cell Biology (INFABIC) at the University of Campinas for the access to equipments and the provided assistance.

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