لخّصلي

Human beings have always involved themselves in various activities to ensure their wellbeing and survival.The level of reactive species in the cellular system may be reduced by antioxidants either by restricting the expression or activities of free radical-producing enzymes such as xanthine oxidase (XO) and NAD(P)H oxidase, or by enhancing the expression and activities of antioxidant enzymes such as glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD) (Aziz et al., 2019).At lower concentrations, they have beneficial effects and indulged in different physiological processes such as redox regulation, mitogenic responses, cellular signaling pathways, and an immune function while at a higher level, these reactive species generate nitrosative and oxidative stress (Phaniendra et al., 2015).To reduce or prevent free radical-directed oxidative damage, the human body has developed an antioxidant defence mechanism that involves free radical scavenging, metal chelating, and enzymatic activities to neutralize the reactive species just after they have formed.The reactive nitrogen and oxygen species (RNS/ROS) play a twofold role as both toxic and beneficial compounds to the organism's system.The growing interest in antioxidants among the public, health professionals, and food scientists is due to their protective function in food items against oxidative deterioration and the organism body against oxidative stress-directed abnormal processes.These potent natural antioxidants are in huge demand for pharmaceuticals/nutraceuticals and as food preservatives.

Human beings have always involved themselves in various activities to ensure their wellbeing and survival. In doing so, the human body has directed the release of different free radicals or reactive substances which are either inhaled or consumed (Engwa, 2018). The reactive nitrogen and oxygen species (RNS/ROS) play a twofold role as both toxic and beneficial compounds to the organism’s system. At lower concentrations, they have beneficial effects and indulged in different physiological processes such as redox regulation, mitogenic responses, cellular signaling pathways, and an immune function while at a higher level, these reactive species generate nitrosative and oxidative stress (Phaniendra et al., 2015). To reduce or prevent free radical-directed oxidative damage, the human body has developed an antioxidant defence mechanism that involves free radical scavenging, metal chelating, and enzymatic activities to neutralize the reactive species just after they have formed. In addition, the consumption of dietary antioxidants can maintain an adequate level of antioxidants in the organism’s body (Lobo et al., 2010). The level of reactive species in the cellular system may be reduced by antioxidants either by restricting the expression or activities of free radical-producing enzymes such as xanthine oxidase (XO) and NAD(P)H oxidase, or by enhancing the expression and activities of antioxidant enzymes such as glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD) (Aziz et al., 2019). The growing interest in antioxidants among the public, health professionals, and food scientists is due to their protective function in food items against oxidative deterioration and the organism body against oxidative stress-directed abnormal processes. These potent natural antioxidants are in huge demand for pharmaceuticals/nutraceuticals and as food preservatives. Effective search for new sources of naturally occurring antioxidants and formulation of new antioxidant compounds need reliable methods for evaluation of the antioxidant activity. Many biological models, food models, and chemical assays have been developed that can measure the reducing power, radical scavenging activity and other related attributes along with overall oxidation inhibition in the more complex biological system and food items. These processes vary in terms of ease of operation, result expression, oxidation initiator, substrate type, and antioxidant mechanism. Selection of a specific or combination of the method is required for the proper assessment of antioxidant potential as a health-enhancing agent or as a food preservative (Shahidi and Zhong, 2015; Chaudhary and Janmeda, 2022a). Thus, the current review updates the current information about free radicals, their origin, types, and antioxidants with their mode of action against reactive species. This paper is found to be very helpful for scientists and researchers who are working on the investigation of the molecular and chemical mechanism of antioxidants. It also benefits the physician who is interested in antioxidant therapy for the cure of diseases.