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Antioxidants that are reducing agents can also act as pro-oxidants. For example, vitamin C has antioxidant activity when it reduces oxidizing substances such as hydrogen peroxide; [93] however, it will also reduce metal ions such as iron and copper [94] that generate free radicals through the Fenton reaction.
The free radical theory of aging states that organisms age because cells accumulate free radical damage over time. [1] A free radical is any atom or molecule that has a single unpaired electron in an outer shell. [2] While a few free radicals such as melanin are not chemically reactive, most biologically relevant free radicals are highly ...
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. [1] [2] With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes.
Free radical mechanisms in tissue injury. Lipid peroxidation induced by xenobiotics and the subsequent detoxification by cellular enzymes (termination). Antioxidants play a crucial role in mitigating lipid peroxidation by neutralizing free radicals, thereby halting radical chain reactions. Key antioxidants include vitamin C and vitamin E. [8]
Oxidative stress mechanisms in tissue injury. Free radical toxicity induced by xenobiotics and the subsequent detoxification by cellular enzymes (termination).. Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. [1]
It is an antioxidant in plants, animals, fungi, and some bacteria and archaea. Glutathione is capable of preventing damage to important cellular components caused by sources such as reactive oxygen species, free radicals, peroxides, lipid peroxides, and heavy metals. [2]
In the 1950s Denham Harman proposed the free radical theory of ageing, which he later expanded to the MFRTA. When studying the mutations in antioxidants, which remove ROS, results were inconsistent. However, it has been observed that overexpression of antioxidant enzymes in yeast, worms, flies and mice were shown to increase lifespan.
After years of frustration over his inability to increase maximum lifespan with antioxidant supplements, Harman came to the conclusion that mitochondria were producing as well as being damaged by free radicals, but that exogenous antioxidants don't enter the mitochondria. And that it is mitochondria that determine lifespan.