br Conflicts of interest br Contributors

Conflicts of interest
Contributors
Introduction Lipid oxidation and enzymatic activities are some of the most significant problems in the food industry. These reactions lead to changes in chemical composition which in turn reduce the quality and shelf life of food products. Most of the antioxidants that currently have found applications in the food industry are low-molecular-weight compounds. Some processes, such as evaporation and leaching, could change their efficiency. Changes in the physical structure of the antioxidants could influence their protective potential and, resulting in food being unprotected against spoilage agents after a short time [1], [2], [3], [4], [5], [6]. Antioxidant polymers, have the advantages of both polymeric and antioxidant systems. To synthesize the antioxidant, chemical or enzymatic reactions can be used. Acquired materials could maintain the antioxidant properties of the antioxidant moiety and, at the same time, afford the good resistance properties of the macromolecular systems. Macromolecular antioxidants are widely used in functional food and dietary supplement areas but, their main usage is in food packaging. Some antioxidant polymers have been found that were able to change the activity of several fibronectin definition involved in cell homeostasis.
Antioxidant polymers as food additives Additives play an important role in food and food products. They are used to preserve flavor in foods, and to blend, thicken, and color them in all production stages such as processing, treatment, packaging, transportation, or storage. Nowadays, rules are stricter than those in the past about the usage of additives in food. FDA limited the use of additives such as BHA and BHT to about 0.02% of the fat or oil content of foodstuff [7]. In the following sections, the application of naturally occurring polymeric antioxidants and antioxidant-polymer conjugates are discussed.
Antioxidant polymers as dietary supplements and functional foods Nutraceutical compounds are one of the largest and fast growing markets in the world [8]. These compounds were introduced as functional foods and dietary supplements in order to reduce several human food-related pathologies, such as cancer and degenerative diseases [9], [10], [11]. Polyphenols are one of the most important groups that have recently been studied widely as natural compounds in nutraceutical supplements [12], [13], [14], [15], [16], [17], [18], [19]. The medicinal usage of the compounds is limited because of their low chemical stability and fast metabolic rate following their administration [20], [21], [22].
Naturally occurring antioxidant polymers In a study, water soluble polyquercetin was prepared using horseradish peroxidases (HRP) catalysis. Water soluble polyquercetin was found to have thermal resistance properties when tested for possible applications in food and drug industry [23]. Similarly, catechin was polymerized by HRP to obtain poly catechin isolate. It was able to scavenge the superoxide anion in a concentration-dependent manner. The inhibition activity of monomeric catechin (CT) starts at 300μM however, it indicated an almost complete scavenging potential at 200μM [24]. Catechin-aldehyde polycondensates indicated a strong inhibition against both monophenolase and diphenolase activities. This feature has been attributed to the high molecular weight of polycondensates. The inhibitory effect strongly depended on the structure of the polycondensates structure and it could influence on their inhibitory potential. It has been demonstrated that high molecular weight polyphenols could control and interact with some digestive enzymes, such as lipase and α-amylase. It is achieved by the formation of hydrophobic and hydrogen bonds [25], [26]. Proanthocyanins have a higher antioxidant potential in comparison to natural antioxidants such as vitamin C and E. It also could control the lipid peroxides in human plasma after exercise and prevent some disease such as atherosclerosis, gastric ulcer and large bowel cancer [27]. CT-acetaldehyde polycondensates also showed stronger inhibitory potential against low-density lipoprotein peroxidation in a catechin unit concentration- dependent manner, compared to monomeric catechin [28].