| https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4310837/ Free Radicals: Properties, Sources, Targets, and Their Implication in Various Diseases
https://www.slideshare.net/alokbharti18/free-radicals-and-antioxidants
https://www.slideshare.net/YESANNA/free-radicales-antioxidants
http://articles.mercola.com/sites/articles/archive/2011/05/16/all-about-antioxidants.aspx
Five 5Types of Free Radicals
==Free radicals can be broken down into five types. The first four types come from oxygen atoms and are called Reactive Oxygen Species (ROS), but the fifth type derives from nitrogen:
Superoxide ion (O): An oxygen molecule with an extra electron that can damage mitochondria, DNA and other molecules.
Hydroxyl radical (OH): A highly reactive molecule formed by the reduction of an oxygen molecule, capable of damaging almost any organic molecule in its vicinity, including carbohydrates, lipids, proteins, and DNA. OH cannot be eliminated by an enzymatic reaction.
Singlet oxygen: Formed by your immune system, singlet oxygen causes oxidation of your LDL.
Hydrogen peroxide (H2O2): Not a free radical itself, but easily converts to free radicals like OH, which then do the damage. Hydrogen peroxide is neutralized by peroxidase (an enzymatic antioxidant). H2O2제거에는 catalase, glutathione peroxidase, peroxiredoxins이 관여
Reactive Nitrogen Species (RNS) (NO): Nitric acid is the most important RNS.
----These various free radical species can damage DNA in different ways.
----They can disrupt duplication of DNA, interfere with DNA maintenance, break open the molecule or alter the structure by reacting with the DNA bases. Cancer, atherosclerosis, Parkinson's, Alzheimer's disease, and cataracts are examples of diseases thought to result from free radical damage. In fact, free radicals are implicated in more than 60 different diseases.
Lipids in cell membranes are quite prone to oxidative damage because free radicals tend to collect in cell membranes, known as "lipid peroxidation." (The lipid peroxide radical is sometimes abbreviated as LOO.) When a cell membrane becomes oxidized by an ROS, it becomes brittle and leaky. Eventually, the cell falls apart and dies.
>>singlet oxygen ==>LDL cholesterol 산화, 결과적으로 심혈관질환 초래---폴리페놀로 중화 가능..
Singlet Oxygen (1O2)...meloperoxidase를 이용해서 H2O2 + Cl- → HOCl + OH·를 생성하고 이어서....HOCL + H2O2 --> 1O2 + H2O+Cl-을 산출하는 중성구 호산구 내 균사멸과정에서 생성.....또한, .lipoxygenases [39], dioxygenases [40], lactoperoxidase에 의해서도 발생 ..........DNA damage [42]와 tissue damage유발
>>superoxide 이온 == *미토콘드리아 호흡과정에서 Complex I and Complex III로부터 중간대사산물로 만들어지기도 하며 *다른 효소들, 예를 들면 xanthine oxidase에 의해서도 발생..*침입세균 탐식/사멸과정에 반드시 필요하므로 NADPH oxidase에 의해 대량생산됨((NADPH유전자부위의 유전변이는 특히 catalase양성균반복감염이 특징인 면역결핍증후군인 만성육아종증 발생과 관계되는데, 이어서 세균의 유전자 조작을 통해서 SOD결핍을 유발시켜 보면 독성을 소실함을 볼 수 있다.((즉, 거의 모든 호기성세균은 SOD를 가지고 있음)...superoxide에 의해 산화-환원 되는 다른 단백질들은 약한 SOD같은 성질을 가지고 있게 됨. **iron-sulfur cluster를 함유하고 있는 효소들을 불활화시킴으로써 free iron을 유리시켜서 결국 펜톤반응 통한 히드록시 라디칼 생성하는데 관여함..((Fe2+훼로스이온 + H2O2 ----> Fe3+훼릭이온 + .OH히드록시라디칼 + OH-수산화이온 )) **HO2*(히드로퍼옥시라디칼)형태에서 PUFA의 지질과산화를 개시함.....또한 carbonyl 성분과 halogenated carbon과 반응하여 그 결과 peroxy radical을 산출
Superoxide anion radical (O2∙) : 가장 중요하며, 광범한 영역에 영향 끼침// mitochondria, DNA and other molecules을 손상시킴.. 효소반응(xanthine oxidase [21], lipooxygenase, cyclooxygenase [22, 23] and NADPH dependent oxidase), 비효소반응(미토콘드리아 내 전자전달계 ETC complex I&III에서 산소에 전자전달하는 과정중에서)으로 발생.....생체분자와의 반응력은 낮은편... pH가 낮을 때(산성??) 두 형태로 존재 가능... hydroperoxyl radical은 가장 중요한 형태로서 charged form (O2•−)보다 더 쉽게 인지질내로 유입 가능함 . 생리적 pH에서 가장 발생이 쉬운 형태는 superoxide여서 환원제로서 역할을 나타내게 되는데, . cytochrome-c 및 ferric-ethylene diaminetetraacetic acid (EDTA-Fe3+)같은 iron complexes 들을 환원시키고 그 결과 3가 철이 2가 철로 바뀜,....또한 산화제로서 작용하기도 하며(2가 훼로스이온이 3가 훼릭이온으로 바뀜), 또한 ascorbic acid와 tocopherol을 산화시킴....또한 두개의 superoxide가 반응하면 과산화수소와 산소가 발생함
Hydroxyl radicals...•OH, neutral form of the hydroxide ion (OH−) [생성기전] **외부 균침습시 Macrophages 및 microglia 면역반응 -->주위에 면역과잉반응 파급 : 자가면역신경질환 유발 **펜톤반응에 의해서 생성..H2O2 + Fe2+ --> Fe3+ OH- ＋ *OH . [세포조직 손상...매우 독성이 큼] 탄수화물, 핵산(유전변이). 지질(과산화), 아미노산( Phe를 m-Tyrosine and o-Tyrosine으로 변환) [파급...퍼옥시 라디칼 생성] •OH(히드록시 라디칼) + RH(알킬화합물)-->H2O + R•(알킬 라디칼 .CH3*)......R• + O2 → RO2*(퍼옥시 라디칼)
Hypochlorous Acid (HOCl) 은 산화 및 염소화 반응에 관여하는 major oxidant로서 myeloperoxidae에 의해 위와 같이 생성되는데, thiols와 ascorbate, urate, pyridine nucleotides, tryptophan등을 산화시키며, 아민류를 염소화시켜서 클로라민으로 변환시킴 ---티로신 기의 염소화, 콜레스테롤 및 불포화지방의 클로르히드린 변화 DNA의 염소화 유발...,
Ozone (O3) 강력한 산화제...체내에서는 염증발생에 중요한 역할을 담당하는 water oxidation경로에 대해 촉매작용하는 항체에 의해 생성 가능..다른 산화라디칼을 생성하는 중간체 역할.....더불어 지질과산화 및 아민류, 알코르 알데히드, 설파히드릴기를 산화시킴..또한 직접 또는 다른 산화라디칼 생성을 통해 간접적으로 염색체손상을 유발시킴.
Peroxyl Radical (ROO∙) : 가장 단순한 형태는 superoxide로부터 나온 perhydroxyl radical (HOO•)로서 지방산산화를 촉발하며, 암발생에도 관여
Enzymatic and Non-Enzymatic Antioxidants
==Antioxidants can be categorized into two types:
>Non-enzymatic antioxidants work by interrupting free radical chain reactions. For example, having vitamin E around may interrupt a chain of free radical activity after only five reactions, instead of its snowballing into 100 reactions. Non-enzymatic antioxidants include vitamin C, vitamin E, plant polyphenols, carotenoids and glutathione (GSH).
Glutathione has been called the “master antioxidant” and is found in every single cell of your body, maximizing the activity of all the other antioxidants.
>Enzymatic antioxidants work by breaking down and removing free radicals. In general, these antioxidant enzymes flush out dangerous oxidative products by converting them into hydrogen peroxide, then into water, in a multi-step process that requires a number of trace metal cofactors (copper, zinc, manganese and iron). You can’t supplement these enzymatic antioxidants orally—they must be produced in your body.
Most antioxidants found in foods and supplements are of the non-enzymatic type. They boost your enzymatic antioxidant defense system by doing a "first sweep," disarming the free radicals, which helps prevent depletion of your enzymatic antioxidants.
---The principle enzymatic antioxidants are the following:
Superoxide dismutase (SOD): Assisted by copper, zinc, manganese and iron, SOD breaks down superoxide (which plays a major role in lipid peroxidation) into oxygen and hydrogen peroxide. SOD is present in nearly all aerobic cells and extracellular fluids.
Catalase (CAT): Converts hydrogen peroxide into water and oxygen (using iron and manganese cofactors), hence finishing up the detoxification process that SOD started.
Glutathione peroxidase (GSHpx) and glutathione reductase: These selenium-containing enzymes help break down hydrogen peroxide and organic peroxides into alcohols, and are particularly abundant in your liver.
As you can see, these powerful enzymes do a wonderful dance in your body that turns toxins into harmless water!
==Water-Soluble and Lipid-Soluble Antioxidants
Another categorization of antioxidants is based on whether they are soluble in water (hydrophilic) or in lipids (hydrophobic). You require both types to protect your cells.
The interior of your cells and the fluid between them are composed mainly of water. But your cell membranes are made largely of fat. As you know, oil and water don't mix. Substances that are soluble in water are not soluble in fat, and vice versa.
>The lipid-soluble antioxidants (such as vitamins E and A, carotenoids, and lipoic acid) are primarily located in your cell membranes, whereas the water-soluble antioxidants (such as vitamin C, polyphenols and glutathione) are present in aqueous fluids, such as your blood and the fluids within and around your cells (the cytosol, or cytoplasmic matrix).
Free radicals can strike the watery cell contents or the fatty cellular membrane, so the cell needs defenses for BOTH. The lipid-soluble antioxidants are the ones that protect your cell membranes from lipid peroxidation.
The fact that antioxidants are so complex and multifactorial has led people to be confused about what antioxidants they should be taking. For example, I have been asked on more than one occasion if it's necessary to take Purple Defense if you are already taking astaxanthin. The short answer is, YES.
Astaxanthin is a lipid-soluble antioxidant, and the antioxidants found in Purple Defense (anthocyanins, polyphenols, resveratrol) are water-soluble antioxidants. As you have now seen, each type has its own special function.
But solubility isn't the only variable among antioxidants. |
제 목 : oxidant-antioxidant
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