Abstract
Essential oils (EOs) and their main constituents, the terpenes, are widely studied, mostly relating to their antioxidant ability and bioactivity, such as antimicrobial, anticancer, anti-inflammatory, and range of other actions in the living systems. However, there is limited information on their bioavailability, especially upon clinical studies. Having in mind both strong biological effects and health benefits of EOs and their specific physicochemical properties (volatility, lipophilic character, low water solubility or insolubility, viscosity, expressed odor, concentration-dependent toxicity, etc.), there is a need for their encapsulation for target delivery. Encapsulation of EOs and their constituents is the prerequisite for enhancing their oxidative stability, thermostability, photostability, shelf life, and biological activity. We considered various carrier types such a (1) monophase and polyphase polysaccharide hydrogel carriers, (2) polysaccharide–protein carriers, and (3) lipid carriers in the context of physicochemical and engineering factors. Physicochemical factors are encapsulation efficiency, chemical stability under gastric conditions, mechanical stability, and thermal stability of carrier matrices. Choice of carrier material also determines the encapsulation technique. Consequently, the engineering factors are related to the advantage and disadvantage of various encapsulation techniques frequently used in the literature. In addition, it was intended to address the interactions between (1) main carrier components, such as polysaccharides, proteins, and lipids themselves (in order to form chemically and mechanically stable structure); (2) main carrier components with pepsin under gastric conditions (in order to form resistant material under gastric conditions); and (3) main carrier components with EOs (in order to enhance encapsulation efficiency), as a necessary precondition for whole process optimization. Finally, different sources for obtaining natural carrier macromolecules are surveyed, especially the agro-waste materials and agricultural and food by-products. This review article highlights the bioavailability aspects of encapsulated EOs and physicochemical and engineering factors concerning natural macromolecule carriers for their target delivery and application.
Highlights
It is assumed that ∼80% of the world’s population relies on plant-based products in official and traditional medicine, where plant products make approximately one-quarter of the total pharmaceutical arsenal (Bhattaram et al, 2002)
Encapsulation of essential oils (EOs) and their individual compounds is necessary for their target delivery, because of low water solubility and stability, high volatility, and some other unfavorable side effects, such as odor, taste, and sometimes the toxicity
It is difficult to predict the overall activity of such complex mixtures as EOs, especially relating their dose and concentration, depending on toxicity effects, frequency of use, and bioavailability
Summary
It is assumed that ∼80% of the world’s population relies on plant-based products in official and traditional medicine, where plant products make approximately one-quarter of the total pharmaceutical arsenal (Bhattaram et al, 2002). The array of enzymatic reactions on fatty acids, such as cleavage, oxidation, lactonization, reduction, or elimination, gives rise to short-chain lactones, alcohols, or aldehydes, whereas cyclization or arachidonic acid results in production of prostaglandins and jasmonates (Dudareva et al, 2006; Baser and Buchbauer, 2010). Amino acids, such as alanine, valine, leucine, isoleucine, and methionine, are the precursors of aldehydes, alcohols, esters, acids, and nitrogen- and sulfur-containing constituents of EOs (Dudareva et al, 2006). Soluble in 5 volumes alcohol; miscible with benzene, chloroform, ether, carbon disulfide, petroleum ether and oils
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