Abstract
Antioxidant action to afford a health benefit or increased well-being may not be directly exerted by quick reduction-oxidation (REDOX) reactions between the antioxidant and the pro-oxidant molecules in a living being. Furthermore, not all flavonoids or polyphenols derived from plants are beneficial. This paper aims at discussing the variety of mechanisms underlying the so-called “antioxidant” action. Apart from antioxidant direct mechanisms, indirect ones consisting of fueling and boosting innate detox routes should be considered. One of them, hormesis, involves upregulating enzymes that are needed in innate detox pathways and/or regulating the transcription of the so-called vitagenes. Moreover, there is evidence that some plant-derived compounds may have a direct role in events taking place in mitochondria, which is an organelle prone to oxidative stress if electron transport is faulty. Insights into the potential of molecules able to enter into the electron transport chain would require the determination of their reduction potential. Additionally, it is advisable to know both the oxidized and the reduced structures for each antioxidant candidate. These mechanisms and their related technical developments should help nutraceutical industry to select candidates that are efficacious in physiological conditions to prevent diseases or increase human health.
Highlights
May a reducing sugar or a non-reducing sugar be in vivo antioxidants? None of two sugars acts as antioxidants in humans [7,8,9], both are oxidized to obtain energy and, in the case of glucose, to () obtain reducing power to be used in innate antioxidant mechanisms
It has been shown that polyphenols may act in the mitochondrial machinery independently of reactive oxygen species scavenging; the authors of this study indicate that “certain polyphenols affect mitochondrial electron transport chain and ATP synthesis” [62]
Indirect, should be considered since plant derivatives may provide pro-oxidants able to upregulate the expression of enzymes of innate detox pathways or, alternatively, regulators of the expression of vitagenes
Summary
Any reduction-oxidation (REDOX) reaction follows well-established chemical laws. Almost any substance can be oxidized or reduced and this depends on a second reagent. A REDOX reaction requires two semi-reactions and two molecules: one that is oxidized (the reductant) and another that is reduced (the oxidant). Any antioxidant molecule is a reductant able to reduce an oxidized reagent. The chemical laws guiding REDOX processes are valid in vivo and in vitro (i.e., in a test tube). “antioxidants” is a word used to refer to substances that provide benefit to humans due to REDOX-related capabilities. It is often assumed that these capabilities are directly exerted on a given tissue or a given oxidative stressor. This paper aims at highlighting the hormetic and mitochondria-related mechanisms of antioxidants action that can be changed by the phytochemical use
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