Quercetin occurs in various fruits, vegetables and many other food components. According to preliminary studies, it has strong antioxidant-, antiviral-, antibacterial-, antihistaminic-, and anti-inflammatory effect. Due to these properties, quercetin is a highly promising material against a wide variety of diseases, including cancer. A major limitation for the clinical application of quercetin is its low bioavailability due to its low solubility in aqueous medium as human body, that makes it necessary to administrate in high doses (50 mg/kg). One way to increase the bioavailability of quercetin is to encapsulate and precipitate it in nanometric scale, using SFEE and/or PGSS drying technology.
SFEE technology is used for producing aqueous suspensions, containing encapsulated valuable material (drug, bioactive compound etc.) in sub-micrometric scale. In SFEE process, an initially prepared oil in water (o/w) emulsion (material of interest is dissolved in the organic phase) is contacted with a supercritical fluid, in order to extract the organic phase from the emulsion. Due to the rapid supersaturation of the dissolution medium by the active compound, it is precipitating in sub-micrometric scale. Supercritical fluid must be chosen to have high affinity for the organic solvent, meanwhile negligible affinity for the active compound.
Using semi-continuous SFEE process (Fig 2) a continuous CO2 flow is maintained, and due to short processing time, degradation effect of quercetin and energy consumption is efficiently decreased. By SFEE process multivesicular aqueous product is obtained, with a main particle size distribution of quercetin around 100 nm encapsulated by the mixture of soy-bean lecithin and Pluroinc L64®, which surfactant materials were added to the initial o/w emulsion to increase its stability and avoid phase separation of emulsion during the process. Using the mixture of surfactant materials quercetin encapsulation efficiency is above 80% with a residual organic content was below 400 ppm in all products.
SFEE process obtained aqueous suspensions were treated by PGSS drying (Fig 3), in order to obtain solid product by the extraction of water content. Using PGSS drying method products become available for long-term storage without significant degradation effect of quercetin, which is rapidly taking place in aqueous medium. Moreover, solid product could be easily convertible back to aqueous suspension by adding water to it. Best process conditions in terms of less residual water content and high efficiency of quercetin encapsulation during PGSS drying process were studied , and in case if good setting of factors in PGSS drying residual water content was decreased below 8 w/w%, meanwhile degradation of quercetin was less than 30%, with an average quercetin encapsulation efficiency of 8.3 mg quercetin / g of sample. A part of aqueous suspensions was treated by lyophilisation instead of PGSS drying, in order to compare quercetin degradation during the processes, and antioxidant activity the solid products obtained by lyophilisation and by PGSS drying. Residual quercetin concentration and antioxidant activity value do not show significant deviation between the two processes, means PGSS drying is an efficient method to produce solid quercetin particles in nanometric scale, encapsulated and protected by soy-bean lecithin as can be seen on Fig 4.
A full report of our results is available at the following link: http://www.sciencedirect.com/science/article/pii/S0896844615000807