Application of an integrated supercritical extraction and impregnation process for incorporation of thyme extracts into different carriers

Abstract

Supercritical carbon dioxide (scCO2) is known as a good solvent for a wide range of bioactive compounds from natural sources. Extraction of bioactive compounds from plant material using scCO2 is a favorable technique for producing solvent-free extracts suitable for a wide range of applications in pharmaceutical, biomedical, cosmetic and food industries. Incorporation of drugs or other bioactive substances into polymeric matrices by conventional techniques is connected to some significant drawbacks (use of organic solvents, undesired substances reactions and/or degradation, low incorporation yields and heterogeneous dispersion). Supercritical solvent impregnation (SSI), and namely impregnation using scCO2, has been proposed as an alternative methodology to overcome most of these problems. The main advantages of this technique are avoidance of organic solvents and possibility to work at relatively low operational temperatures and with hydrophobic drugs/substances which cannot be impregnated by aqueous solution/suspension soaking methods. Additionally, unique physical and transport properties of scCO2 can be used simultaneously for impregnation of biopolymers and tailoring the chemistry and morphology thereof to obtain the desired microstructure of the final product. The present chapter is particularly aimed to demonstrate feasibility of incorporating of thyme extracts into different solid matrices by using a methodology that combines the supercritical fluid extraction (SFE) and SSI. Compared to both processes to be conducted separately, the advantage of using one single integrated process is basically to save energy and time by avoiding an intermediate decompression procedure. Representative commercial carriers with relevance for pharmaceutical, biomedical and food applications (cotton gauze, polypropylene non-woven fabrics, chitosan and starch gels, cellulose acetate and polycaprolactone) were used to test feasibility of thyme extract incorporation by the coupled SFE-SSI process. By setting the relevant parameters of each process separately, the challenge of this methodology aims to harmonize these parameters in order to increase the extraction and impregnation efficiencies as well as to obtain an even distribution of the solute within the solid matrix.