isoquercitrin

Isoquercitrin, also known as quercetin-3-O-glucoside, is a flavonol glycoside in the flavonoid family. It consists of the flavonol quercetin bound at the 3-position to a glucose molecule through a glycosidic bond. Its molecular formula is C21H20O12.

Isoquercitrin occurs in a variety of plants and foods, including onions, apples, buckwheat, berries, and citrus fruits. It is one of several quercetin glycosides that contribute to the color and health properties of plant-derived foods.

In plants, isoquercitrin is produced via the general phenylpropanoid pathway that yields flavonoids. In humans, the glycoside is typically hydrolyzed in the intestine by enzymes or gut microbiota to release quercetin, which is then absorbed and metabolized to glucuronide, sulfate, and methyl conjugates.

Biological activity attributed to isoquercitrin includes antioxidant and anti-inflammatory effects, with additional evidence for vasoprotective, neuroprotective, and anti-cancer potential in preclinical studies. Many of these effects are linked to the activity of quercetin metabolites rather than the glycoside itself.

In foods and supplements, isoquercitrin is used as a source of quercetin activity and as a standardized component of plant extracts. It is generally considered safe as a dietary constituent, though high-dose polyphenol intake can cause gastrointestinal upset in some individuals—and potential interactions with medications should be considered.