Microwave assisted extraction of polyphenols using a coaxial antenna and a cooling system

Abstract

Microwave assisted extraction is a powerful tool for natural compounds extraction from plants. The main goal of our research is to obtain a maximum extraction yield without affecting the chemical structure of the valuable natural compounds. In order to avoid the degradation of the latter, a special equipment has been developed. This equipment allows microwave heating using a slot end coaxial antenna into a microwave applicator provided with an efficient cooling system. Consequently, a high specific absorption rate (SAR) is achieved at low temperatures. A slightly non-uniform heating was observed at lower stirring rates that represents an advantage for the extraction process, keeping the extracted product without any degradation. Using this equipment, polyphenols were extracted from sea buckthorn leaves. For these extracts, total polyphenol content, chemical composition, and antioxidant capacity were determined. The extracts obtained by this procedure present higher polyphenol content with a higher antioxidant capacity than those obtained by conventional methods performed at the same temperature profile and in the same extraction cell.