Ubiquinol

A ubiquinol is an electron-rich form of coenzyme Q. 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 mammals. Coenzyme Q₁₀ exists in three redox states, fully oxidized, partially reduced, and fully reduced. The redox functions of ubiquinol in cellular energy production and antioxidant protection are based on the ability to exchange two electrons in a redox cycle between ubiquinol and the ubiquinone form.

Characteristics

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

Bioavailability

CoQ₁₀ is not well absorbed into the body. Since the ubiquinol form has two additional hydrogens, it results in the conversion of two ketone groups into hydroxyl groups 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.

Health effects

Blood pressure

Studies have shown that Ubiquinol, coenzyme Q10, may reduce systolic blood pressure in adults. A 2025 meta-analysis of randomized controlled trials published in the International Journal of Cardiology Cardiovascular Risk and Prevention concluded that a daily dose of CoQ10 below 200 mg may be an effective adjunctive therapy for the reduction in systolic blood pressure.
A meta-analysis published in the academic journal Advances in Nutrition assessed CoQ10 dosing to lower systolic blood pressure in patients with Cardiometabolic Disorders. The assessment included 1,831 individuals across 26 studies. Conclusions showed that CoQ10 supplements may be potentially effective for clinically reducing SBP in people with cardiometabolic disorders, such as Type 2 diabetes or Dyslipidemia. The dose recommended was 100 – 200mg per day.

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.

Food	Ubiquinol	Ubiquinone
Beef	5.36	25
Beef	40.1	0.4
Pork	25.4	19.6
Pork	2.63	11.2
Chicken	13.8	3.24
Mackerel	0.52	10.1
Tuna	14.6	0.29
Yellowtail	20.9	12.5
Broccoli	3.83	3.17
Parsley	5.91	1.57
Orange	0.88	0.14

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.