The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 11 No. 3 • May 2008

Natural Metabolites of Dietary Quercetin
Target and Protect Macrophages from
Becoming Foam Cells

A very interesting new paper provides experimental evidence to support a novel mechanism whereby dietary flavonoids protect against cardiovascular disease.1 The researchers used quercetin as a prime flavonoid as it is widely distributed in the human diet (onions are particularly rich in it, but it is also found in broccoli, apples, and other foods).

In the standard model of atherosclerosis (well supported by the evidence), macrophages enter the subendothelial linings of arteries, where they ingest modified LDL (especially oxidized LDL), becoming converted into foam cells, a major constituent of atherosclerotic lesions and a source of proinflammatory molecules that promote the development of these lesions. The authors found that pretreatment of RAW macrophages with quercetin-3-glucuronide (Q3GA), a major antioxidative quercetin metabolite, dose-dependently inhibited the accumulation of oxidized LDL in the cells.

Incredibly, the authors showed that Q3GA actually targeted and accumulated in the injured aorta of atherosclerotic plaques, primarily colocalizing with macrophage-derived foam cells—this was determined with an ingenious technique utilizing a monoclonal antibody that specifically bound to Q3GA. They showed that Q3GA dose-dependently downregulated the expression of two major scavenger molecules (SR-A and CD36) which are produced to remove excess cholesterol from foam cells, thus suggesting that the quercetin metabolite might prevent the development of foam cells and, hence, this might be a major source of quercetin’s (and other flavonoids’) protective effects against atherosclerosis. If you take our daily multinutrient supplement, Personal Radical Shield™, at its recommended dosage (3 capsules 4 times a day), you get a daily total of 130 mg of quercetin, which is about three times as much as would be found in a natural vegetarian diet rich in quercetin.


  1. Kawai et al. Macrophage as a target of quercetin glucuronides in human atherosclerotic arteries. J Biol Chem 283(14):9424-34 (2008).

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