Tocols as Antioxidant Molecules in the Agro-Food Field

Introduction

The intake of antioxidant compounds through the consumption of foods and functional foods plays a central role in promoting good health and the proper physiological processes in the human body. The predominant role of these molecules is to prevent the oxidation of natural organic substrates (phospholipids, proteins, DNA) in the body from being attacked by reactive oxygen species (Gęgotek & Skrzydlewska, 2022). All living organisms generate reactive oxygen species from their metabolism, which are involved in normal physiological activities. However, when ROS are produced in large quantities, they can cause significant damage to the organism. Such compounds or reaction intermediates are highly reactive and generate chemical instability. Specifically, the instability of free radicals is due to the presence of a mismatched electron on the outermost orbital with a tendency to interact with electrons from other molecules. Oxidative stress has been associated with several diseases such as diabetes, atherosclerosis, hypertension, respiratory diseases, arthritis, cataract, cancer, cardiovascular diseases etc., as free radicals are implicated in the pathogenesis of these diseases (Engwa et al.,2022; Vaseashta et al, 2022). For this reason, the intake of antioxidant molecules through diet helps to combat oxidative stress (Eggersdorfer & Wyss, 2018, Vaseashta et al, 2021). Studies have shown that dietary intake of tocols (Vitamin E) helps prevent the occurrence of neoplasms and heart disease (Shahidi & De Camargo, 2016). The main antioxidants that are generally present in food and consumed by consumers are vitamin A, vitamin C, vitamin E, polyphenols, and carotenoids. Vitamin A can be present in foods in different molecular forms among which the main ones are retinol, retinoic acid, and retinaldehyde. Foods that contain large amounts of vitamin A are liver, milk, and derivates. Vitamin C, or ascorbic acid is found essentially in large amounts in fruits and vegetables. Regarding vitamin E, the latter comprises two large different molecular classes, specifically tocopherols and tocotrienols. Essentially, vegetable oils, fruits, vegetables, and cereals are the foods that have within them the highest amounts of vitamin E in their different forms (Lee et al., 2018). Tocols are also heat-sensitive molecules and tend during storage, preparation, and cooking to be degraded by oxidative enzymes. Moreover, the amounts of tocols that are degraded during the preparation of food strongly depend on the type of food, the cooking method, and its duration (Diamante et al., 2021). Other studies, on the other hand, point to the possibility that in certain food matrices subjected to cooking processes, degradation of bioactive compounds does not occur, but rather that they are released from the matrix to which they were bound, thus making them more bioavailable (Ruiz-Rodriguez et al., 2008). The term polyphenols denote molecules that belong to the following four major molecular classes: phenolic acids, flavonoids, stilbenoids, and lignans. Foods such as olive oil, chocolate, coffee, tea, fruit and vegetables have been seen to contain significant amounts of polyphenols (Da Silva et al., 2012). Carotenoids, on the other hand, are divided into carotenes and xanthophylls. Carotenes consist of a long chain of carbon atoms, often terminating in a ring and with the variable presence of C-C double bonds (lycopene, β-carotene, etc.). Xanthophylls, on the other hand, consist of chains containing oxygen atoms, which gives them a particular sensitivity to being oxidized (lutein, zeaxanthin, astaxanthin, etc.). Foods that contain large amounts of carotenoids are fruits and vegetables. Focusing on polyphenols, despite having an identical basic structure, are characterized by extremely wide molecular variability. Each of these molecules possesses particular antioxidant activity (Saverini et al., 2016). Generally, most of the antioxidant molecules in food have an apolar molecular structure that allows them to be present in fatty tissues where most of the damage due to oxidative stress occurs. Only a few are water-soluble, namely ascorbic acid, retinol, and some phenols. Antioxidant molecules are by definition, molecules that tend, under certain physico-chemical conditions, to be oxidized very rapidly. High temperatures, the presence of specific enzymes, such as polyphenol oxidase, large quantities of oxygen, and limited quantities of antioxidants under oxidative stress conditions promote the almost instantaneous oxidation of these compounds (Penicaud et al., 2011). On this basis, food is sometimes stored in an unsuitable manner, leading to the degradation of antioxidants and, consequently, to a lower intake of food. It is, therefore, extremely important to correctly conduct all storage operations in order to limit the loss of beneficial molecules as much as possible. Proper respect for the cold chain during transport, sale, and home storage, protection from solar radiation and high temperatures, and removal of oxygen are some of the practices to be used to limit premature oxidation. However, even during food processing, many of these molecules can be degraded due to multiple factors. One of the solutions could be having a process line working at low temperatures and limiting oxygen concentrations. In recent years, many industries have been developing the technique of encapsulation of antioxidant molecules. This technique consists of creating an envelope that protects and optimizes the functional properties of bioactive molecules from technological processes (Beecher, 2003). Encapsulation can also assist with the creation of desirable sensory attributes (e.g., aroma, texture, color, and taste), thus playing a major role in the design and development of novel foods and beverages. Encapsulation is one of the few technologies experiencing continued growth due to its unique potentialities, high versatility, and extensive range of applications. In conclusion, the addition of these molecules or ingredients containing bioactive compounds, together with the adoption of techniques for their preservation molecules during technological processes can contribute to obtaining new foods rich in bioactive compounds that positively influence the health status of consumers.