Optimization of Natural Polyphenol Microcapsule Generation via Sonochemical Process for Pharmaceutical Applications

Abstract

The ultrasonication or sonochemical process is based on the application of ultrasound energy to agitate particles in a liquid medium. It has proven extremely effective in producing core- shell structures with high encapsulation potential. However, for pharmaceuticals applications, the high quantities of microcapsules and the awareness of their statistical mean characteristics are mandatory. Therefore, the optimization of natural polyphenol microcapsule generation via sonochemical process is relevant. For this purpose, representative natural polyphenols were selected and the pH value, natural polyphenol concentration, water/oil phase ratio, ultrasonication power as well as ultrasonication time were varied. The results of this screening led to the assumption that pH is eventually very crucial in natural polyphenol microcapsules generation via sonochemical process. Overall, a 1:1 mixture of an aqueous natural polyphenol solution (0.5% w/v, normalised to approximately 0.05 mmol/mL of the total phenolic OH-group) at pH~12 and the oily phase, first magnetically stirred for five minutes and subsequently treated by ultra-sonication at 160 W (40% amplitude) for ten minutes, was found to be the most efficient set-up for the generation of natural polyphenol microcapsules. With these optimized conditions, it was possible to process and isolate microcapsules from lignins like softwood kraft lignin and softwood lignosofonate and tannins like Acacia mearnsii bark extract, Acacia mearnsii sulfited tannin and Acacia dealbata (winter mimosa) tannin and, more importantly also from epigallocatechin gallate of Camellia sinensis (green tea) and tannic acid of Caesalpinia spinosa that from previous study it was possible to generate only nanoemulsions via the ultrasound assisted method.