Green Extraction Methods for Polyphenols from Plant Matrices and Their Byproducts: A Review

Polyphenols as phytochemicals have gained significant importance owing to several associated health benefits with regard to lifestyle diseases and oxidative stress. To date, the development of a single standard method for efficient and rapid extraction of polyphenols from plant matrices has remained a challenge due to the inherent limitations of various conventional extraction methods. The exploitation of polyphenols as bioactive compounds at various commercial levels has motivated scientists to explore more eco-friendly, efficient, and cost-effective extraction techniques, based on a green extraction approach. The current review aims to provide updated technical information about extraction mechanisms, their advantages and disadvantages, and factors affecting efficiencies, and also presents a comparative overview of applications of the following modern green extraction techniques-supercritical fluid extraction, ultrasound-assisted extraction, microwave-assisted extraction, pressurized liquid extraction, and pressurized hot water extraction-as alternatives to conventional extraction methods for polyphenol extraction. These techniques are proving to be promising for the extraction of thermolabile phenolic compounds due to their advantages over conventional, time-consuming, and laborious extraction techniques, such as reduced solvent use and time and energy consumption and higher recovery rates with lower operational costs. The growing interest in plant-derived polyphenols prompts continual search for green and economically feasible modern extraction techniques. Modern green extraction techniques represent promising approaches by virtue of overcoming current limitations to the exploitation of polyphenols as bioactive compounds to explore their wide-reaching applications on an industrial scale and in emerging global markets. Future research is needed in order to remove the technical barriers to scale-up the processes for industrial needs by increasing our understanding and improving the design of modern extraction operations.