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There are established links between free radicals and more than sixty different human health conditions, including ageing, cancer, diabetes, Alzheimer’s disease, strokes, heart attacks, and atherosclerosis. Consumption of higher levels of dietary antioxidant enzymes and antioxidant molecules-enriched food or antioxidant supplements has been found to reduce the risk of free radical-related health issues. The green halotolerant microalgae Dunaliella can grow in a wide range of saline environments and is a potential natural source for antioxidant production.
Antioxidants | Applications | Ref | |
---|---|---|---|
Natural antioxidants | SOD | Added to cosmetic products to protect against skin damage | [8][12][20][23][24] |
Protect against lipid peroxidation, heat, and cold stress in poultry production | |||
As a therapeutic agent for treatment of inflammatory disorders | |||
Normal cells protector during radiotherapy for cancer patients | |||
CAT | Eliminate excessive H2O2 in the textile industry, pulp, and paper industry used for bleaching fibres and pulp, and as a bactericidal disinfectant in food processing and the pharmaceutical industry | [11][17][25] | |
In aesthetics (mask treatment) to increase cellular oxygenation in the upper layers of facial epidermis | |||
Reducing the risk of diabetes mellitus | |||
GPX | Immune system booster | [10][26] | |
GST | Protective role against neurogenerative diseases | [26][27] | |
Decreases the risk of tumours of the head and neck, oral, cavity and colon | |||
Glutathione | Anti-wrinkle formation, and as a modifier of skin smoothness | [28] | |
Vitamins | As a food preservative and bread improver, protective activity against heart diseases, reduced the risk of colorectal adenomas and prostate cancer, reduction of thyroid hormone levels | [29][30][31][32][33] | |
Flavonoids | As cancer preventive agents, protection against type 2 diabetes Functional food additive | [34][35][36][37] | |
Carotenoid | Anticancer agents, additive to cosmetics and multivitamin preparation Food colouring agent, pro-vitamin A in food and animal feed |
[38][39][40] | |
PUFA | Prevention of heart and inflammatory diseases | [41][42] | |
Synthetic Antioxidants | BHA | Extending the shelf life of vegetable oil, frying oil, animal feed, cereals, chewing gum, potato flakes and cosmetic products | [43][44][45] |
BHT | Increasing the shelf life of animal fats, chewing gum, animal feed, vegetable oils | [44][45] | |
TBHQ | Used as preservative for enhancing storage stability of vegetable oils, margarine, fish oil, fried foods, essential oils, nuts, edible animal fats, butterfat, and packed fried foods | [44] | |
Propyl gallate | As an antioxidant agent in foods and vegetable oil | [44] | |
BHA = butylated hydroxyl anisole; TBHQ = tert-butylhydroquinone; BHT = butylated hydroxyl toluene |
ROS | Reaction | Life Span | Function | Sources of ROS | Scavenging Antioxidants |
---|---|---|---|---|---|
Singlet (1O2) First excited electronic state of O2 |
Chlorophyll triplet state (Chl) is generated sue to insufficient energy dissipation during photosynthesis Chl + 3O2 → 1O2 Reduction of transition metal (Fe3+) O2•− + Fe3+ → 1O2 + Fe2+ |
3 µs (appx.) 4 µs in H2O 100 µs in polar solvents |
Gene up-regulation, molecular defense against photo-oxidative stress | Chloroplast | β-carotene, lycopene, tocopherol, ASc, plastoquinone, and proline |
Superoxide radical (O2•−) One electron reduction of 3O2 |
Reduction of oxygen (3O2) during electron transport during the photosynthesis process in chloroplasts or during oxidative phosphorylation in the mitochondria 3O2 + e− → O2•− 3O2 + Xanthine (Xanthine oxidase) → O2•− + uric acid 3O2 + NADPH (NADPH oxidase) → O2•− + NADP+ + H+ |
2–4 µs | Triggering the formation of more ROS which further participates in membrane lipid peroxidation | PSI in Chloroplast oxidative phosphorylation in mitochondria Peroxisomes Plasma membrane |
SOD, ASc, glutathione (GSH), flavonoids, Cu |
H2O2 Two electron reduction of 3O2 or univalent reduction of O2•− |
Protonation reaction (acidic conditions) O2•− + H+ + HO2• →H2O2 + 2O2 Glycolate + O2 (Glycolate oxidase) → H2O2 + Glyoxylate Fatty acids (β−oxidation) → Acetyl coenzyme + H2O2 |
1 ms | Act as a signaling molecule (low concentration of H2O2), at high concentration of H2O2 triggers tolerance to various stress, as a regulator of physiological processes (photorespiration and photosynthesis) | Chloroplast, Mitochondria, and Peroxisome |
CAT, POD (GPX and APX), peroxiredoxin, ASc, tocopherol, GSH, β-carotene, Se flavonoids, lipoic acid, |
HO2• | Protonation of superoxide ions O2•− + H+ → HO2• |
Attacks PUFA in the negatively charged membrane surface | Mitochondria, microsomes and peroxisomes | ||
HO• (Three electron reduction of 3O2) | Fenton reaction: H2O2 + Fe2+ → HO• + HO− + Fe3+ Haber-Weiss reactions: O2•− + H2O2 → HO• + HO− + O2 |
1 ps | Attack unsaturated fatty acids in membranes | Mitochondria | ASc, GSH, flavonoids, lipoic acid, proline |
Nitric oxide (NO•) | L-arginine + O2 Nitric oxide synthase → NO• + Citrulline | Intercellular messenger, the quencher of O2•−, defense against various protozoa, fungi, and mycobacteria | Peroxisome, cytosol | GSH | |
Peroxynitrite (ONOO−) | NO• + O2•− → ONOO− | React with amino acids residues in enzymes causing inactivation | Peroxiredoxin, Uric acid | ||
Lipid hydroperoxide | Oxidation of PUFA | Tissue injuries and diseases | Mitochondrial membrane PUFA |