INTRODUCTION:

Quinones are widely distributed in nature. They are present in Golgi apparatus, lysosomes, peroxisomes, endoplasmic reticulum and in plasma membrane. This distribution suggests that ubiquinone may be involved in a number of biological processes beyond the respiratory electron transport.(1-3).CoQ10 also known as ubiquinone(UQ), ubidecarenone, Co enzyme Q. this oil soluble, vitamin like substance is present in most eukaryotic cells, primarily in the mitochondria. It is a component of electron transport chain and participates in aerobic cellular respiration, generates energy in the form of ATP. 90% of human energy is generated in this way (4, 5). Therefore organs with highest energy requirements such as heart, liver and kidney have the highest CoQ10 concentrations.(6,7)

There are 3 redox states of CoQ10 fully oxidised (ubiquinone), semiquinone (ubi semiquinone), and fully reduced (ubiquinol).(8,9) The redox functions of CoQ10 in cellular energy production and anti oxidant protection are based on the ability to exchange two electrons in a redox cycle between ubiquinol and oxidised CoQ.(10,11)

BIOSYNTHESIS:

The biosynthesis of UQ is studied in great detail in bacteria and yeast but only to a limited extent in animal tissues.(12-14) The biosynthesis of UQ includes at least nine reactions. The formation of 4-hydroxybenzoate from chorismate is the first committed step in the biosynthesis of UQ in bacteria. Three hydroxylation reactions introduce hydroxyl groups at positions C-6, C-4and C-5 of the benzene nucleus of Q (genes ubiB, ubiH, and ubi).

The same O-methyltransferase with dual specificity (UbiG in E.coli and Coq3 in yeast) catalyzes both O-methylation steps in UQ biosynthesis.(15) Genes involved in CoQ10 production are PDSS1, PDSS2, CoQ2 and CoQ8/CABC1.(16)

COQ10 IN ELECTRON TRANSPORT CHAIN:

CoQ10, found in inner mitochondrial membrane, is the co factor for at least three mitochondrial enzymes (complexes I, II and III) that play a vital role in oxidative phosphorylation. It functions as the only non protein component of electron transport chain (ETC) in addition to not being attached to a protein itself. This unique characteristic enables CoQ10 to move and transfer electrons between flavoproteins and cytochromes. Each pair of electrons processed by the ETC must first interact with CoQ10, which is considered the central rate-limiting constituent of the mitochondrial respiratory chain. Therefore, CoQ10 plays an essential role in adenosine tri phosphate (ATP), or biological energy production. (17-20)

COQ10 concentration in foods and intake: (21)

Beef

Heart	113
Liver	39-50
Muscle	26-40

Pork

Heart	11.8
Liver	22.7-54.0
Muscle	13.8-45.0

Chicken

Heart

116.2-132.2

Fish

Sardine	5-64
Red flesh	43-67
White flesh	11-16
Salmon	4-8
Tuna	5

Oils

Soya bean	54-280
Olive	4-160
Grape seeded	64-73
Sun flower	64-73

Nuts

Pea nuts	27
Walnuts	19
Sesame	18-23
Pistachio nuts	20
Hazel nuts	17
Almond	5-14

Vegetables

Parsley	8-26
Broccoli	6-9
Cauli flower	2-7
Spinach	Up to 10
Grape	6-7
Chinese cabbage	2-5

Fruits

Avocado	10
Black current	3
Strawberry	1
Orange	1-2
Grape fruit	1

CLINICAL USES OF UBIQUINONE

HEART DISEASES:

Patient’s life threatening cardiomyopathy has reduced CoQ10 levels in their heart muscles. When CoQ10 was given as a supplement strength of heart muscles increased and their survival time increased.(22) CoQ10 also decreases blood viscosity and improves blood flow to cardiac muscles in patients with ischemic heart disease.(23) CoQ10 is also used as adjuvant in treatment of congestive heart failure.(24,25) CoQ10 supplement is primarily in the treatment of cardio vascular diseases such as elevated cholesterol levels, high blood pressure, congestive cardiac failure, cardiomyopathy, mitral valve prolapsed, coronary artery bypass surgery and angina.(26-28)

MIGRAINE:

Supplementation of CoQ10 has been found to have beneficial effect on patients with migraine headaches. It has been effective when used in combination with riboflavin. (29)

Blood pressure

CoQ10 is found to be potential in hypertensive patients to lower systolic blood pressure up to 17mm hg and diastolic blood pressure up to 10mm hg without any significant side effects. (30)

CANCER:

Numerous studies have noted the incidence of CoQ10 deficiency in a variety of cancers including breast, lung, prostate, pancreatic and colon cancer. (31-33)CoQ10 is used in the cancer treatment along with relief of side effects. (34-37)

It is also used along with Adriamycin which is used in the cancer treatment without its side effects. (38)

PERIODONTAL DISEASE:

Periodontal and gum disease is caused by plaque forming bacteria that live in the mouth which manifest as inflamed gum tissue that results in loss of teeth. So healing and repair of periodontal tissues requires adequate energy production so it’s given by CoQ10. (39)

A deficiency of CoQ10 at its enzyme sites in gingival tissue may exist independently of and/or because of periodontal tissues. If a deficiency of COQ10 existed in gingival tissue for nutritional causes and independently causes and independently of periodontal diseases, then the advent of periodontal disease could enhance the gingival deficiency of CoQ10.In such patients, oral dental treatment and oral hygiene could correct the plaque and calculus, but not that part of deficiency of CoQ10 due to systemic cause; therapy withCoQ10 can be included with oral hygiene for an improved treatment of this type of periodontal tissue.(40)

However effectiveness of CoQ10 for periodontal diseases is of very poor quality, studies is been conducted to know the better results of CoQ10 on periodontal diseases.(41)The periodontal score was also decreased concluding that CoQ10 should be considered as an adjunct for the treatment of periodontitis in current dental practice.(42)

IN STATIN DRUGS:

The painful or tender myopathy with elevated CPK level due to statin drugs is well described and uncommon. (43, 44)More common is a feeling of lack of energy in people taking these drugs. Since statin blocks mevalonate synthesis. (45)the level of fatigue and feeling of lack of energy in some people taking statin is related to skeletal muscle effects of these drugs is unknown. Thus the unintended adverse effect of the intended pharmacological actions of statin due to inhibition of mevalonate synthesis. People taking statin who describe lack of pep or energy may really lack energy because of deficiency of ubiquinone. On intake of ubiquinone their energy level improved and they felt better. (46)

ANTI-OXIDANT FUNCTION:

The antioxidant nature of CoQ10 derives from its energy carrier function. As a energy carrier, this CoQ10 molecule continuously goes through oxidation reduction cycle. As it accepts electrons it becomes reduced. As it gives up electrons, it becomes oxidized. In its reduced form the CoQ10 molecule holds electron rather loosely, so this CoQ molecule will quite easily give up one or more electrons and thus act as an anti-oxidant.(47)Oxygen free radicals are oxidants normally produced in body during metabolism.CoQ10 acts as an antioxidant ,which protects against low oxygen states which results in large amounts of free radical formation and reduced oxidative distress that often results from surgery.(48)During oxidative stress, interaction of H2O2 with metal ions bound to DNA, generates hydroxyl radicals, and CoQ efficiently prevents oxidation of bases, in particular in mitochondrial DNA.(49)

PARKINSON’S DISEASE:

Parkinson’s disease is a degenerative neurological disorder characterized by tremors, muscular rigidity, and slow movements. Decreased activity of complex I of the mitochondrial electron transport chain and increased oxidative stress in a part of the brain called the substantia nigra are thought to play a role.CoQ10 is the electron acceptor for complex I as well as an antioxidant, and decreased ratios of oxidized CoQ10 have been found in platelets of individuals with Parkinson’s disease. Studies are under process supplementation of CoQ10 in Parkinson’s disease. (50, 51)

CONCLUSION:

The extensive role of ubiquinone in heart diseases, migraine, hypertension, cancer, periodontal diseases and its free radical scavenging property was reviewed. Further research on ubiquinone may prove beneficial to mankind.

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Received on 25.10.2013 Modified on 30.10.2013

Research J. Pharm. and Tech. 7(1): Jan. 2014; Page 114-117