Extraction of active chemical compounds from natural products is one of the most important research areas for pharmaceutical and chemical industries. Traditional techniques used for the solvent extraction of natural products are associated with longer extraction times and lower yields, use of large amount of organic solvents and poor extraction efficiency. Ultrasound can be effectively used to improve the extraction rate by increasing the mass transfer rates and possible rupture of cell wall due to formation of microcavities leading to higher product yields with reduced processing time and solvent consumption. The present work presents an exhaustive overview of different aspects of ultrasound assisted extraction (UAE) of various natural products. Mechanism of UAE has been discussed and recommendations for optimum operating conditions have been reported for maximizing the yield. An overview of different applications of UAE has been also presented. Possible intensification of UAE by coupling with traditional solvent and supercritical extraction processes has also been discussed. Overall it appears that ultrasonic irradiations can be effectively used for intensification of the extraction of important constituents from natural products.

Intensification of extraction of natural products using ultrasonic irradiations—A review of current status

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.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1541-4337.12253

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

In order to identify the chemical constituents of vegetal material it is important that an efficient extraction procedure is followed which provides both an efficient extraction and also limits the decomposition of extracted compounds during the process. Traditional methods such as distillation, solvent extraction and cold compression continue to be used but significant improvements can be achieved with the application of either ultrasound or microwave technologies. In this review we will discuss the development of these methods and review the advantages which can be achieved.

Ultrasonically assisted extraction (UAE) and microwave assisted extraction (MAE) of functional compounds from plant materials

Optimization of microwave-assisted extraction of polyphenols from Myrtus communis L. leaves.

Food wastes are produced by a variety of sources, ranging from agricultural operations to household consumption. About 38% occurs during food processing. At present, the European Union legislation encourages the exploitation of co-products. This valorisation can be achieved through the extraction of high-value components such as proteins, polysaccharides, fibres, flavour compounds, and phytochemicals, which can be re-used as nutritionally and pharmacologically functional ingredients. Extraction can proceed according to solid-liquid extraction, Soxhlet extraction, pressurized fluid extraction, supercritical fluid extraction, ultrasound-assisted extraction, microwave-assisted extraction, pulsed electric field extraction, and enzyme-assisted extraction. Nevertheless, these techniques cannot be used indiscriminately and their choice depends on the type of biomolecules and matrix, the scale processing (laboratory or industrial), the ratio between production costs and economic values of the compounds to be extracted. The vegetable wastes include trimmings, peelings, stems, seeds, shells, bran, residues remaining after extraction of oil, starch, sugar, and juice. The animal-derived wastes include wastes from bred animals, wastes from seafood, wastes from dairy processing. The recovered biomolecules and by-products can be used to produce functional foods or as adjuvants in food processing or in medicinal and pharmaceutical preparations. This work is an overview of the type and amounts of food wastes; food waste legislation; conventional and novel techniques suitable for extracting biomolecules; food, medicinal and pharmaceutical uses of the recovered biomolecules and by-products, and future trends in these areas.

Kung, Chung-Hung Chan, Rozita Yusoff, Gek-Cheng Ngoh, Fabian Wai-L

Papers

Microwave-assisted extractions of active ingredients from plants- A Review