Quercetin
Quercetin is a flavonol, a yellow plant pigment found in onions, apples, capers and the flower buds of the Japanese pagoda tree (Sophora japonica). Commercial quercetin is usually made by extracting rutin from Sophora japonica buds and hydrolyzing off its sugar, then purifying and drying the result. It is sold mostly as quercetin dihydrate, a yellow powder with poor water solubility, with anhydrous and modified forms also available.
Suppliers sell different products under the same name. Specify the one you need.
The standard commercial form, containing about two molecules of water of crystallization, sold at 95% or higher purity.
Dried form with the crystal water removed, giving a higher quercetin content per gram.
Quercetin glycosides made by enzyme treatment of rutin, which dissolve in water much better than quercetin.
Quercetin combined with lecithin or other carriers for capsules and drink mixes; the carrier lowers the quercetin percentage.
Compare each result with your own specification when the lot arrives.
Keep quercetin sealed in light-resistant containers in a cool, dry place. The bright yellow powder stains surfaces and can dust, so keep containers closed and handle with dust control. Shelf life is set by the supplier's specification, with assay and water checked at retest.
Record assay, the basis it is reported on, and water content for each lot, because switching between dihydrate and anhydrous lots changes how much powder delivers a given amount of quercetin. Color can vary slightly between lots.
Facts from regulators and standards bodies, each linked to its source.
GRN 341, for quercetin from Quercegen Pharma, closed in November 2010 with FDA having no questions, noting that some uses may require a color additive listing.
Source: hfpappexternal.fda.gov (opens in a new tab)Health Canada's quercetin monograph for natural health products lists quercetin, quercetin anhydrous and quercetin dihydrate, with citrus bioflavonoids as a source ingredient.
Source: webprod.hc-sc.gc.ca (opens in a new tab)This is general information, not regulatory advice. Status differs by country and by how the ingredient is used, so check the rules for your product and market.
Manufacturers and distributors whose own websites say they sell it.
Distributor · City of Industry, CA
California ingredient supplier that sources branded and commodity ingredients for supplement and food makers, from amino acids and vitamins to magnesium L-threonate and a plant-based vitamin D3.
Suppliers are in alphabetical order and none pays to appear. Each claim is checked against the supplier’s own website on the date shown. Ask for the specification sheet and a recent COA before you order, and confirm details with the supplier.
Common forms include quercetin dihydrate, anhydrous quercetin, enzymatically modified isoquercitrin and lecithin and dispersible forms. Ask each supplier for the specification sheet of the exact grade they quote.
Expect assay (HPLC), water (Karl Fischer), related flavonoids, identity, heavy metals and residual solvents and microbiology, each with its method, specification and result for that lot.
Keep quercetin sealed in light-resistant containers in a cool, dry place. The bright yellow powder stains surfaces and can dust, so keep containers closed and handle with dust control. Shelf life is set by the supplier's specification, with assay and water checked at retest.
GRN 341, for quercetin from Quercegen Pharma, closed in November 2010 with FDA having no questions, noting that some uses may require a color additive listing. Health Canada's quercetin monograph for natural health products lists quercetin, quercetin anhydrous and quercetin dihydrate, with citrus bioflavonoids as a source ingredient.
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