Quercetin 120ct by Pure EncapsulationsWhat Is It? Quercetin belongs to a class of water soluble plant pigments called bioflavonoids that cannot be produced in the human body. It is also considered a phytoestrogen.* Uses For Quercetin Diminishes Histamine Release: Quercetin inhibits the synthesis of enzymes necessary for the release and degranulation of histamine. An in vitro study performed on neutrophils reported that quercetin mediated beta glucuronidase and lysozyme release, as well as