Ubiquinol

 ( Nutrition ) 

A ubiquinol is an electron-rich (reduced) form of coenzyme Q (ubiquinone). The term most often refers to ubiquinol-10, with a 10-unit tail most commonly found in humans.

The natural ubiquinol form of coenzyme Q is 2,3-dimethoxy-5-methyl-6-poly prenyl-1,4-benzoquinol, where the polyprenylated side-chain is 9-10 units long in . Coenzyme Q₁₀ (CoQ₁₀) exists in three redox states, fully oxidized (ubiquinone), partially Redox (semiquinone or ubisemiquinone), and fully reduced (ubiquinol). The redox functions of ubiquinol in Bioenergetics and antioxidant protection are based on the ability to exchange two in a redox cycle between ubiquinol (reduced) and the ubiquinone (oxidized) form.

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Characteristics Because humans can synthesize ubiquinol, it is not classed as a vitamin.

Banerjee R (2025). 9780470177327, John Wiley & Sons. . ISBN 9780470177327

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Bioavailability CoQ₁₀ is not well absorbed into the body. Since the ubiquinol form has two additional hydrogens, it results in the conversion of two into on the active portion of the molecule. This causes an increase in the polarity of the CoQ₁₀ molecule and may be a significant factor behind the observed enhanced bioavailability of ubiquinol.

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Content in foods Varying amounts of ubiquinol are found in different types of food. An analysis of a range of foods found ubiquinol to be present in 66 out of 70 items and accounted for 46% of the total coenzyme Q10 intake in the Japanese diet. The following chart is a sample of the results.

Beef (shoulder)	5.36	25
Beef (liver)	40.1	0.4
Pork (shoulder)	25.4	19.6
Pork (thigh)	2.63	11.2
Chicken (breast)	13.8	3.24
Mackerel	0.52	10.1
Tuna (canned)	14.6	0.29
Yellowtail	20.9	12.5
Broccoli	3.83	3.17
Parsley	5.91	1.57
Orange	0.88	0.14

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Molecular aspects Ubiquinol is a benzoquinol and is the reduced product of ubiquinone also called coenzyme Q₁₀. Its tail consists of 10 isoprene units.

The reduction of ubiquinone to ubiquinol occurs in Complexes I & II in the electron transfer chain. The Q cycle is a process that occurs in cytochrome b, a component of Complex III in the electron transport chain, and that converts ubiquinol to ubiquinone in a cyclic fashion. When ubiquinol binds to cytochrome b, the pKa of the phenolic group decreases so that the proton ionizes and the phenoxide anion is formed.

If the phenoxide oxygen is oxidized, the semiquinone is formed with the unpaired electron being located on the ring.

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