Internship Guideline
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| 3.4 Antioxidant
Life on Earth cannot be possible without oxygen; however, it can be harmful to life by instigating oxidative stress in cells and tissues due to the formation of ROS (reactive oxygen species). Exceptionally high levels of ROS, reactive nitrogen species (RNS), and reactive sulfur species (RSS) cause metabolic malfunctioning, destruction to cellular proteins, nucleic acids (RNA and DNA), lipids and ultimately cell death. Several sources and mechanisms have been advocated, which contribute to the generation of these ROS. Antioxidants are ROS scavengers can shield, scavenge, and repair oxidative damage, thereby defending target assemblies or molecules from oxidative damages. According to the mode of action antioxidants are either primary or secondary antioxidants. Primary antioxidants nullify free radicals by two mechanism, one is by donating an H‐atom known as hydrogen atom transfer (HAT), other is through a single electron transfer (SET) mechanism. These antioxidants are required in lesser amount to neutralize a huge sum of free radicals. For example phenolic antioxidants have high catalytic properties and can be easily regenerated (Zeb, A., 2020). The secondary antioxidants neutralize the ROS through prooxidant catalysts mechanism such as β‐carotene, which neutralize ROS like singlet oxygen by quenching free radical and are thus certainly exhausted. Both primary antioxidants and secondary antioxidants can be either synthetic or natural (Zeb, A., 2020). Synthetic antioxidants, such as butylated hydroxytoluene (BHT), tertbutyl hydroquinone (TBHQ),butylated hydroxyanisole (BHA), and propyl gallate (PG) have been used to prevent lipid peroxidation (LPO), in food products. However, these synthetic antioxidants are cheap and stable at extreme ranges of environmental conditions, but they negatively impact the health causing toxicity that endorses DNA damage. To cope up with such side effects, microorganisms were preferred and since early 1980s, antioxidants from microorganisms were identified and used in healthcare, and agriculture due to their valuable therapeutic efficacy and accessibility (Amany, M. and Abdel-Raheam., 2020). Antioxidants not only protect against ROS but also enhance human physiological functions, consequently assisting to sustain a healthy state and defend against ailments. Living organisms have different antioxidant mechanisms, including enzymatic and non-enzymatic for inactivating ROS. Enzymes, including catalase, glutathione peroxidase and superoxide dismutase are the endogenous antioxidants that control the damage of ROS, whereas carotenes, flavonoids, reduced glutathione, bilirubin, coenzyme Q, and vitamin C, are the sources of exogenous antioxidants. Download 230.5 Kb. Share with your friends:
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