Exogenous Antioxidants are Double-edged Swords

Abstract

Oxidant-antioxidant balance is crucially important in maintaining healthy biological systems. Under physiological conditions, the human antioxidative defense system, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione (GSH), allows the elimination of excess reactive oxygen species (ROS), including superoxide anions (O 2 . ), hydroxyl radicals (HO .), and alkoxyl radicals (RO .). In addition, exogenous compounds with reducing capacity, such as vitamin C, vitamin E, carotenoids, and polyphenols are also essential for intact functioning of endogenous antioxidant defense system. Therefore, there is continuous demand for exogenous antioxidants to prevent oxidative stress. However, higher doses of isolated compounds could act as pro-oxidant either by presenting direct pro-oxidant behavior or by interfering with the normal doses of ROS that is required for normal cell functioning. In this review, synthetic antioxidants among supplementary antioxidants, fruit-rich nutrition and various supplementary products to strengthen our body will be considered and discussed under the light of experimental and epidemiological evidence. Antioxidants in physiological dose ranges are considered to be safe in healthy people and overdoses cause damage via pro-oxidative effects; therefore, the importance of doses of antioxidants, the lower preventive doses that protect healthy individuals from illnesses, and higher therapeutic doses that treat cancer patients will be emphasized in this review.

Effects of Foliar Treatment with a Trichoderma Plant Biostimulant Consortium on Passiflora caerulea L. Yield and Quality

“…The stimulation of bioactive compounds accumulation in P. caerulea leaves, especially of polyphenols and flavonoids, could lead to combinations with reduced safety [83]. High doses of polyphenols proved to be toxic in some cases [84]; therefore, a screening of the safety of treated plant extracts was considered to be necessary. An in vitro method based on cultured cell viability assay was selected for safety screening of the blue passion flower extracts.…”

Antioxidant activity of gamma cobalt-60 irradiated chitosan and vitamin E combination to lead acetate-induced rats

“…This condition worsens due to the presence of several divalent metal ions such as Fe, Cu, and other transition metal ions which will reduce antioxidant activity. Antioxidants provide the most reductive power in the presence of the fenton reaction along with increased OH formations (Koçyiğit & Selek, 2016). This reaction has the potential to increase the detrimental effects from free radical activities.…”

Resveratrol and Its Anticancer Effects

“…While antioxidants reduce oxidative stress at low doses, they have therapeutic doses that can increase the selective death of cancer cells and the effectiveness of standard treatment by increasing ROS production with a prooxidative effect at high doses (65). Studies have been shown that RSV at different concentrations offers favorable suppression of cancer generation and cancer treatment as RSV mediates cytotoxicity in cancer cells by increasing intracellular hydrogen peroxide (H 2 O 2 ) and oxidative stress levels that will cause cell death (66).…”