Antioxidants: A Way to Curb Oxidative Stress

INTRODUCTION

The latest highly infectious COVID-19 disease has already raised a significant danger and severe global public health issue. The pandemic has until now had no unique medical strains, leaving us with the only alternative to maintain our immune system healthy. In addition to genetic causes, food patterns influence our immunity. The immune cell activity of antioxidants against homeostatic stress disorders is widespread. The chemistry of human physiology and metabolism encapsulated a variety of redox reactions and appears dynamically regulated between free and quenching radicality [1]. Certain drugs and xenobiotics are also impaired. Free radicals are reactive chemical species with unpaired electrons in the orbit of other species or molecules that enable them to quickly respond to broad chains of chemical reactions [2] in which free radicals are used to oxidise other chemical species. Free radicals may help combat pathogens when they work properly. Infection is triggered by bacteria. The class of reactive free radicals generally comprises oxygen-free radicals including superoxide anion (O2−.), radical hydroxylic (•OH) and hydrogen peroxide ( H2O2) as reactive oxygen species (ROS) and non-nazote radicals such as nitric oxide (NO) and peroxynitrite (ONOO−). Endogenous and exogenous, synthetic and natural antioxidants are the chemical species that inhibit or minimise the oxidation of others [3] and may donate the electron to a free radical without being dysfunctional. This stabilises the free radical and makes it less reactive. Normally, a good person's human body combines free radical behaviour with antioxidant activity.

OXIDATIVE STRESS

The term "oxidant tension" relates to the disturbance of the oxidant-antioxidant balance [4]. As the equilibrium between free radical generation and antioxidant defenses declines, immune cells adversely affect the body's functions, often contributing to life-threatening cell damage; the immune system is primarily susceptible to oxidative stress. "Chronic stress oxidative to chronic diseases including heart failure, type 2 diabetes and cancer may raise risk. A diet high in antioxidants leads to sustaining a good antioxidant protection that activates the immune system and may effectively mitigate oxidative stress by ending the wide chain chemistry reactions. The most important dietary antioxidants are vitamin C, vitamin E, carotenoids and polyphenols.

The L-enantiomer of ascorbic acid is vitamin C (C6H8O6); the opposite D-enantiomer does not have physiological significance [6]. Being a powerful antioxidant and "scavenger of free radicals throughout the biological system, it contributes to the cellular protection against antioxidants, defends lipid membranes and proteins.. It may function within and outside the cells, becoming water soluble and neutralizing free radicals and preventing free radical damage. It is an ideal supply of electrons for free radicals finding electron stability. It will donate electrons to free radicals and remove their reactivity. Furthermore, vitamin C regenerates another type of vitamin E antioxidant by reducing tocopherol radicals‖ (8). It also interferes in replication of viruses, enhances the

―Vitamin E is the collective term for four tocopherols (α-, β-, γ-, and δ-tocopherols) and four tocotrienols (α-, β-, γ-, and δ-tocotrienols) found in food. Such forms have antioxidant activity, but cannot be interconverted, and the requirement for human vitamin E is fulfilled only by α-tocopherol (figure 1). Vitamin E is an essential fat-soluble antioxidant which scales peroxyl radicals and ends the oxidation of poly-unsaturated fatty acids (PUFAs). The chain reaction of peroxyl radical development is halted if vitamin E reacts with α-tocopherol rather than lipid hydroperoxide, and further oxidation of PUFAs in the membrane is prevented. Tocopheroxyl radicals—produced from α-tocopherol and peroxyl radicals are reduced by vitamin C or glutathione‖ (10) [Scheme 2] (11)

Carotenoids are A diverse omnipresent group of natural isoprenoid polyene pigment types with a perfectly straight symmetrical skeleton formed by a tail-to-tail connection of the two moieties of the C20. The C40 hydrocarbon linear backbone is vulnerable to numerous structural adjustments. Till date more than 700 carotenoids have been described. The most important include β-carotene, α-carotene, δ-carotene , γ-carotene, lycopene, δ-carotene [Figure 2] (12), lutein, zeaxanthin, β-cryptoxanthin, α-cryptoxanthin, neurosporene etc. They are known to be very efficient physical and chemical quenchers of singlet oxygen (1O2) (13), peroxyl radicals add rapidly to polyenes structural unit of carotenoids, where the resulting C-radicals are strongly stabilized by resonance [Scheme 3] (14) playing the role of potent scavengers of other reactive oxygen species (ROS) thereby reduces oxidative stress.

This natural product category is a particularly complex group of compounds with phenolic structural properties which includes many classes and subgroups of phenolic compounds. Polyphenols were classified according to their chemical composition, their biological function and their sources. It can be grouped into four major classes on the basis of chemical structure: flavonoids, phenolic acids, polyphenolic amides and other polyphenols. Querquetin, catechin and anthocyanin, such as apples, onions, black chocolate and red chocolate, are in flavonoids of subgroups including falvones, flavonols. It represents around 60% of all polyphenols (15) and has the general structural backbone C6–C3–C6 of which all units are phenolic. No flavonoid polyphenolic acids constitute nearly 30% of all polyphenols(15) and further categorised into two subgroups, gallic acid and ferulic acid. Phenolic acids are non-flavonoid polyphenolic substances.

Polyphenolic amides, polyphenols with an amide element. Two other groups are avenanthramids, chilli pepper capsaicinoids and oats. Capsaicinoids such as capsaicin have major antioxidant and anti-inflammatory properties and modulate the oxidative function of cell defence. Avenanthramides include an antioxidant that prevents LDL oxidation (16)

Ellagic acid and its berry fruit compounds comprise, for instance, strawberries or raspberries, orange-containing resveratrol and lignans contained in linens, several grain links and curcumins. In an electron or hydrogen molecule, polyphenols are used to neutralise free radicals. In quercetin, for example (3, 4′dihydroxyl), the strongly conjugated mechanism and some hydroxylated patterns are considered important for non-oxidants behaviours, where the chain end of the reaction is rapidly broken off by the free radical (R). Polyphenols hinder free radical growth and destroy active organisms and free reactivity, stopping chain reactions. The Fenton reaction rate can be decreased by transitional metal chelation such as Fe2 +, which can resist oxidation by highly reactive hydroxy radicals. Polyphenols should not function on their own. Polyphenols effectively serve as co-antioxidants and are involved in the regeneration of essential vitamins (16).

1. Hajian S. (2015). Positive effect of antioxidants on immune system. Immunopathol Persa; 1(1):e02.

stress 3. Ayoub, Zeenat & Mehta, Archana (2014). Medicinal plants as potential source of antioxidant agents: A review. Asian Journal of Pharmaceutical and Clinical Research. 11. 50. 10.22159/ajpcr.2014.v11i6.24725. 4. De Las Heras, N., Martín Giménez, V. M., Ferder, L., Manucha, W., & Lahera, V. (2015). Implications of Oxidative Stress and Potential Role of Mitochondrial Dysfunction in COVID-19: Therapeutic Effects of Vitamin D. Antioxidants, 9(9), 897. 5. Healthy Foods High in Antioxidants (2015). Retrieve from https://www.healthline.com/nutrition/foods-high-in-antioxidants 6. The Vitamin C. Molecule Antioxidant Properties.(2015).Retrieved from https://www.worldofmolecules.com/antio 7. Retrieved from https://pubs.rsc.org/en/content/articlehtml/2015/ra/c4ra13315c 8. Pehlivan, F. (2017). Vitamin C: An Antioxidant Agent. Vitamin C. doi: 10.5772/intechopen.69660 9. Retrieved from https://www.researchgate.net/figure/Chemical-structure-of-tocopherol-and-tocotrienol-analogues_fig1_11339969 10. Lee, G. & Han, S. (2014). The Role of Vitamin E in Immunity. Nutrients, 10(11), 1614. DOI: 10.3390/nu10111614 11. Retrieved from https://lpi.oregonstate.edu/mic/vitamins/vitamin-E 12. Retrieved from https://www.researchgate.net/figure/Chemical-structures-of-carotenoids_fig1_233429458 13. Fiedor, J. & Burda, K. (2014). Potential Role of Carotenoids as Antioxidants in Human Health and Disease. Nutrients, 6(2), pp. 466-488. DOI: 10.3390/nu6020466 14. Foti, Mario & Amorati, Riccardo. (2009). Non-phenolic radical-trapping antioxidants. The Journal of pharmacy and pharmacology. 61. pp. 1435-48. 10.1211/jpp/61.11.0002. nols#what-they-are 16. Tsao R. (2010). Chemistry and biochemistry of dietary polyphenols. Nutrients, 2(12), pp. 1231–1246. https://doi.org/10.3390/nu2121231 17. Papuc, C., Goran, G., Predescu, C., Nicorescu, V., & Stefan, G. (2017). Plant Polyphenols as Antioxidant and Antibacterial Agents for Shelf-Life Extension of Meat and Meat Products: Classification, Structures, Sources, and Action Mechanisms. Comprehensive Reviews In Food Science And Food Safety, 16(6), pp. 1243-1268. DOI: 10.1111/1541-4337.12298

Department of Chemistry, Dr. Ambedkar Govt. P. G. College, Unchahar- Raebareli (UP) [Affiliated to CSJM University, Kanpur (U.P.)] nsabeeha11@rediffmail.com