Biological effects of essential oils - A review

Phenolics and polyphenolics in foods, beverages and spices: Antioxidant activity and health effects – A review

As particle design is presently a major development of supercritical fluids applications, mainly in the pharmaceutical, nutraceutical, cosmetic and specialty chemistry industries, number of publications are issued and numerous patents filed every year. This document presents a survey (that cannot pretend to be exhaustive!) of published knowledge classified according to the different concepts currently used to manufacture particles, microspheres or microcapsules, liposomes or other dispersed materials (like microfibers):

RESS: This acronym refers to ‘Rapid Expansion of Supercritical Solutions’; this process consists in solvating the product in the fluid and rapidly depressurizing this solution through an adequate nozzle, causing an extremely rapid nucleation of the product into a highly dispersed material. Known for long, this process is attractive due to the absence of organic solvent use; unfortunately, its application is restricted to products that present a reasonable solubility in supercritical carbon dioxide (low polarity compounds).

GAS or SAS: These acronyms refer to ‘Gas (or Supercritical fluid) Anti-Solvent’, one specific implementation being SEDS (‘Solution Enhanced Dispersion by Supercritical Fluids’); this general concept consists in decreasing the solvent power of a polar liquid solvent in which the substrate is dissolved, by saturating it with carbon dioxide in supercritical conditions, causing the substrate precipitation or recrystallization. According to the solid morphology that is wished, various ways of implementation are available:

GAS or SAS recrystallization: This process is mostly used for recrystallization of solid dissolved in a solvent with the aim of obtaining either small size particles or large crystals, depending on the growth rate controlled by the anti-solvent pressure variation rate;

ASES: This name is rather used when micro- or nano-particles are expected; the process consists in pulverizing a solution of the substrate(s) in an organic solvent into a vessel swept by a supercritical fluid;

SEDS: A specific implementation of ASES consists in co-pulverizing the substrate(s) solution and a stream of supercritical carbon dioxide through appropriate nozzles.

PGSS: This acronym refers to ‘Particles from Gas-Saturated Solutions (or Suspensions)’: This process consists in dissolving a supercritical fluid into a liquid substrate, or a solution of the substrate(s) in a solvent, or a suspension of the substrate(s) in a solvent followed by a rapid depressurization of this mixture through a nozzle causing the formation of solid particles or liquid droplets according to the system.

The use of supercritical fluids as chemical reaction media for material synthesis. Two processes are described: thermal decomposition in supercritical fluids and hydrothermal synthesis.

We will successively detail the literature and patents for these four main process concepts, and related applications that have been claimed. Moreover, as we believe it is important to take into account the user's point-of-view, we will also present this survey in classifying the documents according three product objectives: particles (micro- or nano-) of a single component, microspheres and microcapsules of mixtures of active and carrier (or excipient) components, and particle coating.

http://www.tuleoffice.com/images/editor/File/pdf/book/nano/s5%20im-web.pdf

Particle design using supercritical fluids: Literature and patent survey

http://www.ipb.pt/~htgomes/FCT115275/Ref23.pdf

Sub- and supercritical fluid extraction of functional ingredients from different natural sources: Plants, food-by-products, algae and microalgae: A review

Supercritical extraction and fractionation of natural matter is one of the early and most studied applications in the field of supercritical fluids In the last 10 years, studies on the extraction of classical compounds like essential and seed oils from various sources: seeds, fruits, leaves, flowers, rhizomes, etc, with or without the addition of a co-solvent have been published Supercritical extraction of antioxidants, pharmaceuticals, colouring matters, and pesticides has also been studied The separation of liquid mixtures and the antisolvent extraction are other processes that can perform very interesting separations Mathematical modelling has also been developed and refined for some of these processes The objective of this review is to critically analyze traditional and new directions in the research on natural matter separation by supercritical fluids extraction and fractionation

Supercritical fluid extraction and fractionation of natural matter

Phenols, proanthocyanidins, flavones and flavonols in some plant materials and their antioxidant activities

Micronization of drugs using supercritical carbon dioxide.

Major recent advances. Particle formation and design of solid particles and powdery composites with unique properties is at the moment a major development of supercritical fluids (synonyms: dense gasses, dense fluids, high pressure) applications. This review will focus on recent advances and on fundamentals of these processes and their applications.

Particles formation and particle design using supercritical fluids

Isoamyl acetate was successfully synthesized from isoamyl alcohol in supercritical carbon dioxide by enzymatic catalysis. First, the impact of the acyl donor was investigated. Among several reactants, including acetic acid and two different acetates, acetic anhydride gave best yields. Then, two different immobilized lipases (Novozym 435 from Candida antarctica and Lipozyme RM-IM from Rhizomucor miehei ) as biocatalysts for the above-mentioned reaction were compared. An esterification extent of 100% was obtained in continuous operation using acetic anhydride as acyl donor and Novozym 435 as enzyme. The amount of enzyme preparation was optimised to 6.25 g/mol alcohol. The effect of substrates load in the solvent was investigated. Operating at a CO 2 /substrates molar ratio below 7.0, the conversion of alcohol decreased, probably due to an inhibitory effect on enzyme by high concentration of acetic anydride or by produced acetic acid. Pressure in the range of 8–30 MPa showed no effect on this reaction, while an increase in temperature (over 313 K) led to lower production of isoamyl acetate. Novozym 435 was very stable not finding any loss of activity during one month of continuous operation. Finally, carbon dioxide was compared to a conventional organic solvent ( n -hexane). Initial reaction rate was higher in SC-CO 2 , although final esterification extent was similar in both media.

Zeljko Knez

Papers

Phenols, proanthocyanidins, flavones and flavonols in some plant materials and their antioxidant activities

Micronization of drugs using supercritical carbon dioxide.

Particles formation and particle design using supercritical fluids

Enzymatic synthesis of isoamyl acetate with immobilized Candida antarctica lipase in supercritical carbon dioxide

High pressure extraction of vitamin e-rich oil from silybum marianum