Hesperetin

Hesperetin is a flavanone, a type of flavonoid, that occurs in citrus fruits as the aglycone form of the glycoside hesperidin. It is found in small to moderate amounts in the edible portions of oranges, lemons, limes, and mandarins, and is particularly concentrated in the peels and in citrus-derived extracts. In humans, hesperetin is typically released from hesperidin by gut microflora or during food processing.

Chemically, hesperetin belongs to the class of flavanones characterized by a 15-carbon skeleton consisting of two aromatic rings (A and B) joined by a heterocyclic C ring. It is substituted with hydroxyl groups and a methoxy-containing moiety, which contribute to its antioxidant properties and lipophilicity. Its natural occurrence is as the aglycone form; hesperidin is the glycoside form common in citrus fruits.

Biosynthesis of hesperetin in plants involves the flavonoid biosynthetic pathway, arising from phenylpropanoid metabolism. In humans, dietary hesperetin primarily exists as hesperidin, which is deglycosylated by intestinal bacteria to yield hesperetin, and then rapidly conjugated to glucuronides or sulfates for systemic circulation.

Pharmacology and health-related research indicate that hesperetin has antioxidant and anti-inflammatory activities in vitro, and has been explored for potential cardioprotective and anticancer effects. However, clinical evidence remains limited, and bioavailability is relatively low due to poor solubility and extensive metabolism. Safety at typical dietary intakes is generally considered acceptable, while high-dose supplement use requires caution and further study.