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Home > Supplements > Antioxidants >
Quercetin is a potent and versatile flavonoid and
phytonutrient. Bromelain is an enzyme complex derived from the pineapple
stem. (Note: G.D.U. stands for “Gelatin-Digesting Units,” a commonly
accepted measure of enzyme activity.)
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Down-regulates the Body’s Response to Environmental Challenges Quercetin
is a member of the flavonoid family, a diverse group of low
molecular-weight compounds found throughout the plant kingdom.
Flavonoids exhibit numerous biological activities, many of which are
directly beneficial to human health. Quercetin, which belongs to the
“flavonol” subgroup, is one of the most versatile and important
flavonoids. Quercetin has a broad range of activity, much of which stems
from its interaction with calmodulin, a calcium-regulatory protein.1
Calmodulin transports calcium ions across cellular membranes, initiating
numerous cellular processes. Quercetin appears to act as a calmodulin
antagonist.1 Through this mechanism, quercetin
functions at the cell-membrane level with a membrane-stabilizing action.2
Quercetin inhibits calmodulin-dependent enzymes present at cell
membranes such as ATPases and phospholipase, thereby influencing
membrane permeability.3 Quercetin affects other
calmodulin-dependent enzymes that control various cellular functions,
including the secretion of histamine from mast cells.4
A number of investigations have corroborated quercetin’s ability
to reduce histamine secretion from mast cells in various tissues, and
also from basophils.5,6,7,8,9,10 Quercetin
modifies the body’s response to antigenic substances.* Suppression of
histamine secretion from mast cells is one of quercetin’s most
clinically important effects. Quercetin acts on ATPase at the membranes
of histamine-containing granules in mast cells.3
Mast-cell degranulation and subsequent release of histamine into the
bloodstream is an integral part of the body’s response to environmental
challenges. Maintains Tissue Comfort by Regulating Enzymes* Quercetin’s
enzyme-inhibiting action extends to enzymes such as phospholipase, which
catalyzes the release of arachidonic acid from phospholipids stored in
cell membranes.4,10 Arachidonic acid serves as the
key substrate for substances such as thromboxanes, inflammatory
prostaglandins and leukotrienes. In addition, quercetin inhibits the
enzymes cyclooxygenase and lipoxygenase, which catalyze the conversion
of arachidonic acid into its metabolites.4,10,11,12
Reducing levels of these metabolites, as well as histamine
levels, is beneficial in maintaining the normal comfort level of body
tissues and structures. Quercetin has also been shown to limit the
function of adhesion molecules on endothelial cells.13
Adhesion molecules are involved in physiologic processes that
influence tissue comfort.13 Bromelain is a complex
substance derived from the pineapple stem largely composed of
proteolytic (protein-digesting) enzymes. Bromelain acts by a variety of
mechanisms to help maintain tissues in a normal state of comfort.14,15
Several investigators, including Taussig16
and Ako, et. al.,17 have presented evidence that
bromelain is a fibrinolytic agent, i.e., it induces the breakdown of
fibrin, a plasma protein that blocks tissue drainage. The generally
accepted mechanisms involve direct proteolysis of fibrin by bromelain
and activation of plasmin, a serum protease.16
Plasmin acts on fibrinogen (the precursor to fibrin), forming peptides
which stimulate PGE1, a prostaglandin that helps maintain tissue
comfort.16 Helps Maintain Health of Blood Vessels
by Modifying Oxidation of LDL Cholesterol* — Quercetin’s Antioxidant
Action Quercetin is a versatile and effective antioxidant that scavenges
a variety of free-radicals such as hydroxyl and lipid peroxy radicals.18
Quercetin also chelates ions of transition metals such as iron,
which can initiate formation of oxygen free radicals.18
LDL cholesterol is vulnerable to oxidation by lipid peroxides. Oxidized
LDL is absorbed by macrophages and arterial endothelial cells, leading
to the formation of “foam cells,” and eventually plaque deposits, in
arterial walls. Quercetin has been shown to protect LDL from oxidation,
both by lipid peroxides and transition metal ions.19
Helps Maintain Normal Blood Viscosity* Quercetin inhibits blood platelet
aggregation (clumping), by potentiating PGI2, an anti-aggregatory
prostaglandin, and by raising platelet cyclic AMP levels.20
Human studies have revealed that bromelain also reduces platelet
aggregation.21 These properties qualify both
quercetin and bromelain as valuable dietary ingredients for maintaining
cardiovascular health.* Bromelain May Enhance Quercetin Absorption In
addition to the actions described above that support the effects of
quercetin, bromelain may also assist the absorption of quercetin in the
G.I. tract. (Quercetin is generally believed to be poorly absorbed,
although a recent study by Hollman et. al.,22
which concluded that humans do in fact absorb appreciable amounts of
quercetin, contradicts this assumption.) Studies have shown that
bromelain enhances absorption of antibiotics, presumably by increasing
permeability of the gut wall.23, 24 Given that
quercetin is a low molecular-weight compound, it is plausible that
simultaneously ingested bromelain likewise enhances quercetin
absorption.
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Suggested Use: 1 or 2 capsules three times daily, preferably 30 to 60
minutes before meals.
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1. Nishino, H., et. al., “Quercetin interacts with calmodulin, a calcium
regulatory protein.” Experientia 1984;40:184-5.
2. Busse, W.W., Kopp, D.E., Middleton, E., “Flavonoid modulation of
human neutrophil function.” J. Allergy Clin. Immunol. 1984;73:801-9.
3. Havsteen, B,. “Flavonoids, a class of natural products of high
pharmacological potency.” Biochemical Pharmacology 1983;32(7):1141-48.
4. Middleton, E., “The Flavonoids.” Trends in Pharmaceutical Sciences
1984;5:335-8.
5. Otsuka, H. et. al., “Histochemical and functional characteristics of
metachromatic cells in the nasal epithelium in allergic rhinitis:
Studies of nasal scrapings and their dispersed cells.” J. Allergy Clin.
Immunol.1995;96:528-36.
6. Fox, C.C., et. al., “Comparison of human lung and intestinal mast
cells.” J. Allergy and Clin. Immunol. 1988;81:89-94.
7. Pearce, F.L., Befus, A.D., Bienenstock, J., “Mucosal mast cells III.
Effect of quercetin and other flavonoids on antigen-induced histamine
secretion from rat intestinal mast cells.” J. Allergy and Clin. Immunol.
1984;73:819-23.
8. Middleton, E. Drzewiecki, G., Krishnarao, D., “Quercetin: an
inhibitor of antigen-induced human basophil histamine release.” J. of
Immunology 1981;127(2):546-50.
9. Bennett, J.P., Gomperts, B.D., Wollenweber, E.,“ Inhibitory effects
of natural flavonoids on secretion from mast cell and neutrophils.”
Arzneim. Forsch/Drug Res. 1981;31(3):433-7.
10. Middleton, E. Drzewiecki G., “Naturally occurring flavonoids and
human basophil histamine release.” Int. Archs Allergy appl. Immun.
1985;77:155-7.
11. Yoshimoto, T. et. al., “Flavonoids: potent inhibitors of
arachidonate 5-lipoxygenase.” Biochemical and Biophysical Research
Communications 1983;116(2):612-18.
12. Della Loggia, R., et. al., “Anti-inflammatory activity of
benzopyrones that are inhibitors of cyclo- and lipo-oxygenase.”
Pharmacological Research Communications 1988; 20(Supp. V):91-94.
13. Middleton, E., Suresh, A., “Quercetin inhibits
lipopolysaccharide-induced expression of endothelial cell intracellular
adhesion molecule-1.” Int. Arch. Allergy Immunol. 1995;107:435-6.
14. Taussig, S.J., Batkin, S., “Bromelain, the enzyme complex of
pineapple (Ananas comosus) and its clinical application.” An Update
Journal of Ethnopharmacology 1988;22:191-203.
15. Lotz-Winter, H., “On the pharmacology of bromelain: An update with
special regard to animal studies on dose-dependent effects.” Planta
Medica 1990;56:249-53.
16. Taussig, S.J., “The mechanism of the physiological action of
bromelain” Medical Hypothesis 1980;6:99-104.
17. Ako, H. Cheung, A.H.S., Matsuura, P.K., “Isolation of a fibrinolysis
activator from commercial bromelain.” Arch. Int. Pharmacodyn.
1981;284:157-67. | |
