Quercetin and Isoquercetin are two kinds of common natural active products. They have similar names, but they have different functions and efficacy, and It’s also very different in use.

  1. Quercetin:

Quercetin is a flavonol, which exists in a variety of vegetables and herbs. It contains many beneficial biological activities, which can help healthy cell proliferation, cardiovascular immunity.

Quercetin has antioxidant properties, can eliminate free radicals, help cell regulation, promote DNA integrity, and so on. Besides, quercetin can also help the body maintain enough glutathione levels in oxidative stress to support immune regulation.

Quercetin is the basic structure of many flavonoids, such as rutin and Isoquercitrin. At the same time, quercetin ring structure will exist as a part of larger flavonoid molecules, such as hyperglycemia in Hypericum, flavonoid glycosides in Ginkgo biloba, etc. Quercetin is often added to supplements because it is easier to extract from rutin. However, quercetin rarely exists directly in nature and is not easily absorbed on the absorption surface of the small intestine. Its absorption occurs in a slower and more inefficient passive diffusion process.

  1. Isoquercitrin:

Isoquercetin mainly exists in the form of glucoside in nature, usually in the 3 ‘or 4’ position of the glucoside chain. Apples and onions are one of the most abundant food sources of quercetin glucoside, especially quercetin-3-glucoside, Isoquercitrin, and Isoquercetin.

Isoquercitrin and Isoquercetin are two interchangeable terms, even in the eyes of experts, because their molecules are very similar in structure.

Functionally, the two molecules are almost indistinguishable. Studies have shown that Isoquercetin has higher bioavailability than quercetin or rutin.

  1. Three different places:

(1). Chemical structure:

Isoquercetin is a glycoside, while quercetin is an aglycone, It is also known as glycosyl. From figures 1 and 2 followings, quercetin has the same skeleton as Isoquercetin. In terms of chemical synthesis, Isoquercetin is the addition of glucose to the skeleton.

Extraction process: rutin was extracted from high-quality Sophora japonica, and then the rutin was desaturated. One sugar (rhamnose) was removed to form Isoquercetin, and two sugars (glucose + rhamnose) were removed to form quercetin.

(2).Water solubility

Quercetin is completely insoluble in water, while Isoquercetin is soluble in water.

(3).Bioavailability

Isoquercetin has been proved to have higher bioavailability and a faster absorption rate than quercetin or rutin, which is about twice as fast as quercetin and ten times higher than rutin. The glucose part of Isoquercetin accelerated the molecular uptake and transformation to quercetin.

Product nameBioavailabilityCoefficient
Quercetin2%1x
Isoquercetin12%6x