Nepal Journal of Biotechnology. Dec. 2018 Vol. 6, No. 1: 74-91 ISSN 2091-1130 (Print)/ISSN 2467-9319 (online) REVIEW ARTICLE Technologies for the Extraction, Separation and Purification of polyphenols – A Review Shyam Suwal1* and Alice Marciniak2 1 Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej Denmark 2Institute of Nutrition and Functional Foods (INAF), Department of Food Sciences, Université Laval, Québec, Canada Abstract Polyphenols are high molecular weight, organic molecules mainly found in plant kingdom. They are mostly known for their positive impact on health, specifically for their antioxidant activity. Indeed, they are widely studied for the prevention of multiple diseases such as cancer, inflammatory, cardiovascular and neurodegenerative diseases. Nevertheless, extractions of these growing interest molecules remain challenging using conventional methods such as solvent extraction. That is why recent researches have focused on improving the extraction of polyphenol by using different technologies such as ultrasound, microwave, pressurized liquid, pulsed electric field, supercritical fluid and high hydrostatic pressure. In the current context, the assisted- extraction should demonstrate their potential to improve the extraction efficiency while being cost-effective and with a low environmental impact. To this end, technologies ought to, for instance, increase the solubility of polyphenol and the permeability of the cell wall. Consequently, this review is focused on the use and potential of these technologies to improve polyphenol extractions from plants as well as their purification using various methods. It discusses of the advantages and disadvantages with some examples of all these technologies assisted-extraction in comparison with conventional extraction method as well as purification technology. Keywords: Polyphenols, Conventional extraction process, Emerging technologies *Corresponding Author Email: [email protected] Introduction them very interesting as an ingredient of The prevention and treatment of chronic diseases functional foods or nutraceuticals [3]. Different mainly cardiovascular diseases (CVD) and cancer beneficial roles on human health such as are the major challenge in modern day health care antihypertensive anticancer, neuroprotector etc. system. About 60% of deaths were caused by the have been confirmed [6]. Therefore, an immense chronic diseases in 2001 and according to the interest of researchers on polyphenols mainly in study of World Health Organization (WHO) the their physiological roles (both in vitro and in vivo), heart disease will overcome the infectious disease their extraction processes and product by 2020 [1]. Therefore, the burden (economical as development in an industrial scale can be noticed. well as social) of chronic diseases is huge and However, extraction of such molecules from the tends to increase day by day alarming an urgent complex plant matrices is the rate limiting factor. need of preventive measures. Undoubtedly, the Several methods of polyphenol extraction from primary cause of these diseases is associated with variety of food and food by-products exist such as unhealthy diets. solvent (Soxhlet), ultrasound assisted, microwave There is an increasing interest in diets and assisted, pressurized liquid, pulse electric field, nutrition which has resulted in an increased supercritical fluid and high hydrostatic pressure importance and beliefs in functional foods and extractions. The extraction methods not only affect nutraceuticals [2]. Several bioactive molecules the input cost, final productivity and purity but (peptides, vitamins, polyunsaturated fatty acids also their biological activity in laboratory assay [7, and polyphenols) have been isolated from food 8]. A cost effective and environment friendly sources of plant as well as animal origin and are method are thus desired for the isolation of claimed to possess health benefits against CVD polyphenols. A separation and purification and cancer [3-5]. Very diverse nature of process is another vital step in product polyphenol in their chemical composition and development with polyphenols. Therefore, the their wide spread prevalence in edible plant make ©NJB, Biotechnology Society of Nepal 74 Nepjol.info/index.php/njb Nepal Journal of Biotechnology. Dec. 2018 Vol. 6, No. 1: 74-91 Surname of autheor et al. present study aims to review different techniques used for the isolation of Figure 1: Chemical structure of principal polyphenols (adapted from [3]). polyphenols published in the literature. In from a simple to polymerized structure and may addition, methods of fractionation and be found in a complex form with some purification of extracted polyphenol or free carbohydrate, protein or plant substances making polyphenols present in liquid beverages are also them highly insoluble [10]. Furthermore, a single discussed may contain several polyphenols whose concentration (several mg to few g per kg or L), Polyphenols and health claims stability and activity vary from one to another. Polyphenols are readily available in the plant- More than 8000 phenolic compounds are known derived food sources consumed by human in to exist and about 4000 flavonoids have been daily basis such as fruits, vegetables, cereals, tea, identified [11]. Further details about different wine etc. [3]. They are responsible for the major type of phenolic compounds in food sources, their organoleptic properties such as color and taste of characteristics and relevance can be found in the plant-derived food and beverages [9]. Plant literature [3, 12]. polyphenols comprise of diverse groups of Polyphenols are very well known as the most compounds that make them difficult to be abundant antioxidant in the diet and they have characterized except for some well-known ones been claimed to possess potential benefits against whose structure, chemical composition and cardiovascular diseases, cancer and functionality are well defined. Ample of neurodegenerative diseases in vitro as well as in polyphenol structures (having several hydroxyl vivo [6, 13, 14]. Due to the vast structural diversity groups in aromatic ring) are found in plants are of polyphenols many of them have not yet been therefore classified according to the number of identified and characterized consequently the phenol rings to one another. They can be mainly functional mechanism are not well established. classified into the phenolic acids, flavonoids Amongst them, the tea polyphenol: catechin also (flavones, anthocyanidins), stilbenes, and lignans known as epigallocatechin-3-gallate (EGCG) is (cinamic acid) as shown in figure 1. Each of these well characterized and a large number of phenolic compounds can be subclassified researches are focused on its mode of action. according to the type of heterocycle involved. The Lorenz [14] discussed the different mechanisms of chemical nature of phenolic compound can vary ©NJB, Biotechnology Society of Nepal 75 Nepjol.info/index.php/njb Nepal Journal of Biotechnology. Dec. 2018 Vol. 6, No. 1: 74-91 Surname of autheor et al. anticancer (apoptosis, inhibition of tumor growth 1. Conventional Solvent extraction and inhibition of telomerase), antioxidant (free Solvent extraction (SE) is one of the conventional radical scavenging, chelation of metal ions, methods of extraction of bioactive molecules from inhibition of ROS producing enzyme and plant sources but is still widely used for the reduction of inflammatory cytokines), extraction of various natural bioactive antihypertensive (vasodilation) and compounds specially the phenolic compounds neuroprotective (antineuro inflammatory effect, from various sources [20]. Pretreated plant activity of EGCG in the cellular and molecular material (washing, drying, etc.) are exposed to levels. In addition, a detail pharmacokinetic study varieties of solvents such as, water, hexane, ether, (absorption, distribution metabolism and chloroform, acetonitrile, benzene, ethanol and elimination) of tea polyphenols is recently methanol which take up the molecules of interest reviewed by Clifford et al. [15]. (polyphenols). However, the efficiency of solvent Extraction process extraction methods is affected by the solvent used (solubility of phenolic compounds depend on the Due to positive effects on human health, phenolic solvent type or its polarity) and the nature of compounds (isolated form or in extract) could be phenolics (degree of polymerization) and their used as food supplements (functional food) or interaction with other plant or food constituents nutraceuticals. To do so, a cost-effective methods [10]. The choice of extraction techniques have to for the extraction and separation of polyphenols is take into consideration of the location of phenolic necessary. A lot of research has focused on the compounds in the plant, most of which are stored analysis of biological activities and in the vacuoles only extractable by alcoholic or characterization of phenolic compound and the organic solvents except that are bound to extraction process are often ignored. The insoluble carbohydrate or protein [21]. Soxhlet extraction and isolation of polyphenols remain extraction also known as solid-liquid extraction is challenging especially due to structural one of the first techniques known to be used for complexity and instability (degradation and the extraction of polyphenols compounds [22]. reaction during processing) [9, 11]. Therefore, the This technique is more often considered as a efficiency