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.

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Response surface methodology was applied to optimize microwave-assisted extraction (MAE) of total phenolic content (TPC) and antioxidant activity from fruiting bodies of Coriolus versicolor mushroom, and to compare its efficiency with conventional reflux extraction. A central composite design was employed for the optimization of three MAE parameters including extraction time (X 1 , min), ethanol concentration (X 2 , %) and microwave power (X 3 , W) for the highest yield of TPC and antioxidant activity measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and ferric ion reducing antioxidant power (FRAP) assays in C. versicolor extracts. The optimum conditions were predicted as 3.8 min extraction time, 40% ethanol concentration and 125 W microwave power to obtain maximum values of TPC (470 mg GAE/100 g dm) and antioxidant activity measured by DPPH (773 mM TE/ g dm), ABTS (2,930 mM TE/g dm) and FRAP (1,710 mM TE/g dm) assays, which were statistically verified by comparing with the experimentally observed values. PRACTICAL APPLICATIONSIn this study, microwave-assisted extraction (MAE) showed significant potential as a green extraction method for obtaining Coriolus versicolor mushroom extract rich in polyphenols with higher antioxidant activity as compared to the extracts obtained by reflux extraction. Furthermore, MAE resulted in reduced consumption of energy, time and solvent with higher extraction yield and efficiency. This work demonstrated further feasibility studies on MAE of phytochemicals including polyphenols-rich extracts at industrial scale. Moreover, successful application of response surface methodology has opened future research avenues for optimization of bioactive components from other mushrooms of medicinal importance.anticancer and immune-enhancing properties (Cui and Chisti 2003;Szeto 2008;Sun et al. 2014). Hot water extract of C. versicolor is famous as one of the most effective immune support supplements (Mushroom Science 2015). Multistep hot water extraction has been mainly reported to obtain extract from C. versicolor (Cui and Chisti 2003;Szeto 2008). The RE method for extraction of bioactives components involves 4 h of extraction time at 95 6 58C (MFDS

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