What are “free radicals”?

• A free radical is an atom or molecule with one or more unpaired electrons
• Free radicals are very unstable and try to gain stability by gaining the required electron; therefore, free radicals are very reactive
• They react with other chemical compounds by capturing the required electron and thus triggering chain reactions with the formation of further radicals.
• These reactions are unregulated and unpredictable – they can generally damage all biological structures and molecules
• Particularly affected are:
  cell components (e.g. damage to genetic material in the cell nucleus or DNA)
  • Fats (oxidation of lipoproteins) and carbohydrates
  • Proteins / Enzymes
  • Amino acids such as L-cysteine ​​(glutathione building block)

What do “oxidation” and “reduction” mean?

• An antioxidant gives an electron to the free radical and thereby neutralizes it à the free radical becomes a “healthy” molecule again
• Through the release of electrons, the antioxidant is again oxidized (radicalized) and must then be reduced again, etc.

What is “oxidative stress”?

• If there is an imbalance between oxidation and reduction or more free radicals (oxidants) than antioxidants, this is referred to as oxidative stress for the body.

How are free radicals formed?

Free radicals are formed both exogenously (environmental factors) and endogenously (through the body’s own processes):

• Endogenous:
  • Cellular Energy Production in the Mitochondria: in the mitochondria, oxygen is reduced to water. However, this does not happen completely: some of it becomes free radicals (compounds of oxygen with hydrogen or nitrogen). To prevent the reaction of oxygen and hydrogen from causing an explosive gas effect in the body, the electrons are transferred in several stages - this happens in the so-called "respiratory chain" (= electron transport chain). This consists of several redox systems connected in series, in which an electron is removed from molecules by free radicals, which in turn radicalizes them, etc. Example: NADH is oxidized by free radicals to NAD+ with the release of H+
  • Cellular Immune Defense and Inflammation (“Oxidative burst”): in the mitochondria of activated phagocytes (phagocytic cells such as granulocytes and macrophages that absorb viruses and bacteria), free radicals (e.g. H2O2 and hydroxyl radicals) are formed to support the killing of phagocytosed germs (viruses, bacteria) à If the immune system is overly activated (e.g. due to autoimmune diseases) and there is a simultaneous lack of antioxidants, oxidative stress occurs!
  • detoxification (Detoxification phase I): in order for toxic substances to be excreted, they must first be radicalized, i.e. made "reactive". The products of phase I are therefore usually more aggressive than the actual toxin, so that rapid detoxification or excretion in phase II is important. In phase II, polar hydrophilic molecules such as glutathione or cysteine ​​are then attached to the metabolites of phase I, making them available in water-soluble form for excretion via the kidneys.
  • homocysteine ​​metabolism: Formation of H2O2 radicals e.g.through interactions with transition metals or enzymes
  • glucooxidation (in case of high glucose levels or diabetes) with the formation of H2O2
  • Chronic diseases in general: lead to inflammation and increased radical release
  • Physical stress (e.g. physical work, competitive sports)
• Exogenous:
  • sun and UV light
  • ozone O3
  • Radioactive environmental radiation (e.g. when flying)
  • Radioactive medical radiation (e.g. therapy, mammograms and other diagnostics)
  • Medications (e.g. contraceptives, paracetamol, antibiotics, cytostatics)
  • cigarettes and alcohol
  • Other environmental pollutants, e.g. metals, smog, nitrogen oxides, car exhaust fumes, solvents, pesticides & other chemicals

What damage can free radicals cause?

• DNA damage
• Malregulation of carbohydrate, amino acid and fat metabolism
• acceleration of aging
• reduction in performance
• Increased risk of so-called “free radical diseases” (this mainly affects tissues with high oxygen turnover such as heart, skeletal muscles, eye lens, etc.):
  • Neurodegenerative diseases such as Alzheimer's disease
  • arteriosclerosis
  • allergies
  • aging processes
  • Amyotropic lateral sclerosis (ALS): disruption of SOD degradation and destruction of motor nerve cells by free radicals
  • Cataractogenesis macular degeneration
  • diabetes
  • cancer
• Acceleration of the progression and increase in the severity of many diseases
• Increased risk of recurrence in many diseases

What positive functions do free radicals have in the body?

• Training function: Small amounts of radicals train the redox system
  (promote performance, antioxidant production and resilience), comparable to a vaccination
• immune function:
  • Macrophages and granulocytes form redox systems in mitochondria; free radicals kill bacteria and protozoa in interaction with lytic enzymes
  • High doses of vitamin C with radical activity have a cytotoxic effect against cancer cells
  • Radical-producing chemotherapeutic agents and radiation kill cancer cells; ATTENTION: Therefore, antioxidants should not be taken during chemotherapy and/or radiotherapy!
• Signaling function: Radicals can act as signaling substances, e.g. in inflammation (stimulation of the transport of immune cells to the site of inflammation), in the growth of nerve cells (e.g. after spinal cord injuries, in the context of adult neurogenesis) and in wound healing

What are antioxidants?

• Antioxidants are “radical scavengers”, i.e. they give an electron to the radical and thus reduce it (and are usually oxidized themselves in the process)
• When reduced, they have an OH, SH or NH group and react faster with radicals than other biological structures (e.g.: 1 molecule of the antioxidant vitamin E protects up to 1000 fatty acid chains!)
• Antioxidants act synergistically and regenerate each other: they form a network enzymatic and non-enzymatic antioxidants: Vitamin C, E, coenzyme Q10 (ubiquinone as oxidized, ubiquinol as reduced form), glutathione and alpha-lipoic acid regenerate (reduce) each other after oxidation

Enzymatic (higher molecular weight)	Non-enzymatic (low molecular weight)
• Formed in the body (“endogenous”) • Effects depend on genetics (enzymopathy) and synthesis rate • High reaction speed • Do not become radicalized during detoxification (no chain reactions!) • Require cofactors for effect • Are not available indefinitely	• Mostly supplied through food • Effects dependent on supply • Low reaction speed • Become radical during detoxification (must be defused!) • Quick replacement possible • Are (theoretically) available indefinitely

What are the most important antioxidant enzymes?

• superoxide dismutases (SOD)
  • Catalyze the superoxide radical conversion (O2- ) into H202 + O2
  • with copper (Cu)/zinc (Zn) as cofactor in the cytoplasm and extracellular space
  • with manganese (Mn) as a cofactor in mitochondria
• catalases
  • Catalyze the reduction of H202 to H20 (prevention of hydroxyl radicals)
  • With iron (Fe) as cofactor
  • in liver, skin, kidney cells and erythrocytes
• peroxidases
  • Catalyzing in the aqueous cell environment reduction of H202 to H20
  • Selenium-independent peroxidases (iron (Fe)-dependent)
  • Selenium-dependent phospholipid hydroperoxide glutathione peroxidase
  • in erythrocytes, liver, lungs and kidneys

What are the most important non-enzymatic antioxidants?

• carotenoids
  • beta-carotene: antioxidant effect through inactivation (so-called "quenching") of reactive compounds
  • zeaxanthin
  • lutein
  • lycopene
• Polyphenols --> have an antioxidant effect mainly due to the phenolic OH group; the number of OH groups influences the antioxidant effect
  • Resveratrol --> 3 OH groups
  • quercetin --> 5 OH groups and therefore particularly strong antioxidant effect
  • Matcha: has an ORAC value of 1,711 units/g, the highest known ORAC value in a natural product (ORAC stands for "Oxygen Radical Absorbance Capacity", i.e. the ability to reduce oxygen radicals)
  • Brahmi:  Scientific studies have primarily investigated the antioxidant effect of Brahmi in relation to neurodegenerative diseases (cf. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4564646/ )
• vitamins
  • Vitamin C (water-soluble)
  • vitamin E (fat-soluble)
  • Tocopherol E-OH is oxidized to tocopheroxyl radical and then reduced again to tocopherol E-OH by vitamin C or glutathione as a hydrogen donor
  • "Vitamin E contributes to  to protect DNA, proteins and lipids from oxidative damage." (official health claim)
  • vitamin B2 (water-soluble): "Vitamin B2 (riboflavin) helps protect cells from oxidative stress." (official health claim)
  • Vitamin A (fat-soluble)
  • Vitamin K (fat-soluble)
• thiols (with SH group)
  • glutathione
  • L-cysteine
  • alpha-lipoic acid
  • can pass the brain barrier and regenerate used antioxidants such as vitamin C, E, coenzyme Q10 or glutathione; therefore a central component of synergistic antioxidant complexes
  • Deutsche Apotherkerzeitung: "A clinical study in patients with mild to moderate Alzheimer's dementia showed that the additional administration of alpha-lipoic acid to acetylcholinesterase inhibitors extremely slows the progression of the disease." (cf. https://www.deutsche-apotheker-zeitung.de/daz-az/2009/daz-3-2009/liponsaeure-bei-alzheimer-demenz )
• Other sulfur-containing amino acids
  • taurine
  • L-methionine
• Medicinal mushrooms, especially Cordyceps: In laboratory tests, the antioxidant potency of Cordyceps extract was demonstrated (cf. https://pubmed.ncbi.nlm.nih.gov/11114006/ )
• coenzyme Q10
• L-carnitine
• NADP (active vitamin B3)
• cofactors of enzymatic antioxidants
  • Selenium (Se)
  • zinc (Zn)
  • iron (Fe)
  • manganese (Mn)
  • copper (Cu)

Which foods are particularly rich in antioxidants?

antioxidant	Groceries
vitamin C vitamin E selenium glutathione β-carotene lycopene sulforaphane resveratrol spermidine	lemons, oranges, grapefruit, kiwi olive oil, wheat germ oil, wheat germ Wheat germ, sesame, whole grain products, sea fish, redfish Avocado, watermelon, asparagus, broccoli, spinach carrots, tomatoes, apricots tomato juice broccoli Red wine (moderate!), berries, peanuts wheat germ, soy

Indicators and risk factors for oxidative stress (the more questions are answered with “yes”, the greater the risk of oxidative stress; does not replace diagnostics!)

• complaints
  • I am often tired.
  • I suffer from lack of motivation.
  • I have more than 3 colds per
  • My physical and mental performance is not satisfactory.
• lifestyle habits
  • I smoke.
  • I drink more than 20g of alcohol on several days a week.
  • I often spend time in the sun and/or visit tanning salons.
  • I do intensive sports several times a week.
• stresses
  • I am regularly stressed.
  • I am exposed to environmental pollution (e.g. amalgam or radiation).
  • I often go on diets.
  • I work a lot on the computer.
• diseases and health risks
  • overweight
  • lipid metabolism disorders
  • diabetes mellitus
  • heart disease
  • Rheumatic diseases
  • intestinal diseases
  • respiratory diseases
  • allergies
  • cancer
• medication intake
  • painkillers
  • hormone preparations
  • anticontraceptives
  • chemotherapeutic agents
• Nutrition
  • I eat fresh fruit and gently prepared vegetables less than 3 times a day.
  • I drink less than 2 glasses of fruit or vegetable juice per day.
  • My diet does not regularly contain milk and dairy products.
  • I drink less than 1.5 liters of liquid per day.
  • I don't eat fish regularly.

Diagnosis of Oxidative Stress

• antioxidant side
  • Determination of the most important antioxidant blood levels
    • Non-enzymatic such as glutathione, vitamin C + E, coenzyme Q10 and the cofactors selenium and zinc
    • Enzymatic such as superoxide dismutase SOD, glutathione peroxidase GPx
  • Screening to determine antioxidant protection: Total antioxidant capacity TAS / Antioxidative potential TEAC (ability to react with free radicals)
    • In the laboratory: e.g. patient serum (with antioxidants) + defined amount of free radicals; measurement of the remaining amount of radicals after detoxification (dye reaction):
      Initial amount – remaining amount = Antioxidative potential (normal value: 1.3-1.77 mmol/l blood)
    • In practice: e.g.FORD (Free Oxygen Radicals Defense) in capillary blood
• radical side
  • Recording of lipid peroxidation: malondialdehyde (MDA-LDL as a long-term value over 7-10 days), since aldehyde is a measurable degradation product of free radicals
    • 4-Hydroxnonenal HNE (alkenal/aldehyde): oxidative damage of polyunsaturated fatty acids
    • 8-Ispoprostane F2 α(8-iso-prostaglandin F2 α): oxidative damage to prostaglandin synthesis (from arachidonic acid)
    • 2-Propenal (acrolein/aldehyde): oxidative damage to polyunsaturated fatty acids
  • Detection of oxidative damage to genetic material: Deoxyguanosine test (DNA oxidation / 8-OHdG) (excretion of 8-hydroxy-deoxyguanosine as a result of oxidative damage to nucleic acids/DNA in urine; biomarker for the assessment of individual mutagenic/carcinogenic effects of oxidative stress )
  • Detection of protein oxidation: Nitrotyrosine (oxidation of tyrosine with peroxynitrite)
  • Electron spin resonance ESR: Direct detection of radicals (principle: absorption of microwave radiation by unpaired electrons; but not established due to lack of availability and short lifespan of the radicals)

Examples of applications of antioxidants

• aging processes
• Sports (performance-oriented)
• Cardiovascular diseases (e.g. arteriosclerosis)
• Neurologist & Psychologist (e.g. Alzheimer's disease, Parkinson's disease, ALS, schizophrenia) (3)
• immune system and inflammation in general (rheumatism, periodontitis, acute pancreatitis)
• drug-induced disorders
• Other environmental pollution (e.g. alcohol, smoking, pollutants)
• diabetes
• respiratory diseases
• eye diseases (e.g. cataracts)
• Reproductive Medicine and Infertility (2)
• Cancer prevention (Caution: Antioxidants should be avoided during chemotherapy/radiotherapy, as they can prevent the (in this case) desired cell death! (1)

(1) Antioxidants and cancer risk

A five-year follow-up study conducted following the SU.VI.MAX study from France with 12,741 adults (primary prevention, placebo-controlled, double-blind, blood level monitoring) confirmed that the long-term administration of an antioxidant Complex in nutritional doses (vitamin C 120 mg/day, vitamin E 30 mg/day, beta-carotene 6 mg/day, selenium 100 mcg/day, zinc 20 mg/day) in persons with an insufficient supply of antioxidants in the form of of fruits and vegetables resulted in a 31% reduced risk of cancer and a 37% lower mortality rate (cf. https://pubmed.ncbi.nlm.nih.gov/20104528/ ).

(2) Antioxidants and Infertility

Oxidative stress damages sperm. The damage can be repaired by the body’s own antioxidant defense
reduced. Partners of infertile men who took antioxidants as part of a reproductive program experienced an increase in birth rates. See:  Review of 34 randomized controlled trials with 2876 couples; Showell et al, Antioxidants for male subfertility; Cochrane 2012; DOI: 10.1002/14651858.CD007411.pub2 (“Oxidative stress may cause sperm cell damage. This damage can be reduced by the body's own natural antioxidant defenses.Antioxidants can be part of our diet and taken as a supplement. It is believed that in many cases of unexplained subfertility, and also in instances where there may be a sperm-related problem, taking an oral antioxidant supplement may increase a couple's chance of conceiving when undergoing fertility treatment.”)

(3) Antioxidants and dementia
Mitochondrial radicals are partly responsible for the formation of amyloid-ß aggregates. Amyloid
ß in turn leads to mitochondrial dysfunction and to an increase in ROS (cf. Leuner K et al.; mitochondrion derived ROS lead to inhanced amyloid-beta-formation; Antioxid Redox Signal 2012; 16; 1421-1433; “Conclusion: Several lines of evidence show that mitochondrion-derived ROS result in enhanced amyloidogenic amyloid precursor protein processing, and that Aβ itself leads to mitochondrial dysfunction and increased ROS levels. We propose that starting from mitochondrial dysfunction a vicious cycle is triggered that contributes to the pathogenesis of sporadic AD.”