I originally published this article on my site Nat_anti_hiv on Yahoo:

Start of Article

I decided to go out onto the World Wide Web to try and find some answers
to my questions about absorption and anti-viral activity of Quercetin. Please
remember that at this stage, these conclusions are somewhat speculative.
I came to the following tentative conclusion:

High-dose Vitamin C is an essential companion for Quercetin therapy.

There are reasons for this, none of which are absolutely established.

2. Vitamin C is essential for the anti-viral activity of Quercetin

The other possibility that needs to be given serious consideration is that
high Vitamin C may also increase the already long half-life of Quercetin.
Since I have not been able to find any references to high-dose C and
Quercetin on the Web, we may be on our own on that. If it was true that
high C resulted in a longer half-life, then this would imply that daily
maintenance doses may need to be even lower than my original proposal.
It may even be that you only need to take a little Quercetin every few days,
once you have established Quercetin saturation. The best way to decide
many of these things, will be if there is a test for blood level of
Quercetin. I will continue to carefully experiment. My motto will be, "with
Quercetin and high Vitamin C: "it's better to under-dose Quercetin, rather
than over-dose"

The other implication of the possibility that Vitamin C increases half-life is
for over-dose situations. When you are building up to effective blood
concentration, the long half-life is valuable. If you have overdosed, you
want to do the opposite - increase decay of Quercetin, i.e. shorten half-life.
This means removing the possible inhibitor of decay - principally Vitamin C.
In overdose situations, you quit not just the Quercetin, but all
nutritional supplementation especially Vitamin C. It would also be
logical to avoid all foods high in Vitamin C. You'd probably only need to
do this for a couple of days, hopefully. In any case, for short periods, it
can't be harmful.

I have made some recommendations for supplemental nutrition in a previous
post. I realize that some people may not be able to afford this. Based on my
current research, for those who want to experiment, and are willing to take
the risk, I would recommend that if you do nothing else, take lots of
Vitamin C and a mineral supplement to get magnesium. They're both cheap.
It will save money on the Quercetin, because you can use it at lower dose
when you take Vitamin C. Be very aware that if you mega-dose Vitamin C,
the dosage of Quercetin required will be much smaller than is currently
recommended. If my research and personal experience is valid, it is absolutely
essential for absorption and anti-viral activity of Quercetin. Dosage of
Vitamin C? It is very difficult to say what the minimum required dosage would
be. My guess is 5 grams, but preferably 10 grams. I take 10-20 grams per day.
If you get severe flatulence at any dose of Vitamin C, this is simply a sign that
you have ingested more Vitamin C than the body needs, and the excess has
been left over in the gut. Since vitamin C is acidic, it produces gas. You simply
cut back your dose, until that doesn't happen. Do this when you're home alone.
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I simply typed "Quercetin" into the Yahoo search engine. Try doing this search
yourself sometime! I found that Quercetin is widely known and used for many
other health problems and quite alot is known about it. It is generally regarded
as safe, with no serious side effects! This has not been my experience!

My current opinion is that my use of high doses of Vitamin C (10-20grams/day)
in conjunction with Quercetin has resulted in very high absorption, so I am
getting side effects at doses that are generally recommended. I believe this also
means that a good blood concentration of Quercetin can result from what are
generally regarded as low doses. There are recommendations that as well as
Vitamin C, magnesium and bromelain are required for absorption. I do indeed take
Magnesium, (I supplement practically all known micro-nutrients!) but not bromelain.
I believe that since I am getting excellent absorption, the bromelain is not necessary.

Although alot more research needs to be done, I think anyone who uses Quercetin
for any purpose, needs to know about the possibilities of Vitamin C. Also it should
be realized that when you have good absorption, lower doses are required,
and that it is easy to overdose.

I see very little knowledge of the very long half-life of Quercetin. It is vital to
consider this when determining dosage. As I noted in the previous post about
the dangers of overdose, it seems to me that the strategy of establishing an initial
blood concentration, and then simply replacing every day the loss due to natural
causes. Since the half-life is about a day, then after the initial dose, you are looking
at half the initial dose on a daily basis, to maintain more or less even blood levels.

If indeed high Vitamin C results in even longer Quercetin half-life, then daily
maintenance dose will be even lower.

I see nothing about the uses of high Vitamin C with Quercetin on the Web. We
may be in new territory there.

I think these conclusions are somewhat substantiated by some of the articles that
I have reproduced below.
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Anti-Viral Abstracts
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The following article is a real gem. It gives some crucial information about the
anti-viral activity of Quercetin. Although it does relate to poliovirus, I would
think it also applies to HIV.

The following extract is taken from the site:

http://vir.sgmjournals.org/cgi/content/abstract/69/7/1749

Begin Extract
Antiviral activity of flavones and potentiation by ascorbate
R Vrijsen, L Everaert and A Boeye
Department of Microbiology and Hygiene, Vrije Universiteit Brussel, Belgium.
We compared the anti-poliovirus activities of three flavones, quercetin, luteolin
and 3-methylquercetin, which differ only at ring position 3. 3-Methylquercetin
was the most potent compound. Quercetin exhibited antiviral activity only when
protected against oxidative degradation by ascorbate. The antiviral activity of
luteolin was comparable to that of ascorbate-stabilized quercetin.

End Extract
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Absorption Abstracts and Extracts
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This site does recommend Vitamin C be taken with Quercetin, but I
personally think they have it the wrong way round. You take Vitamin C
to support and potentiate the Quercetin, not the other way round!
In my experience the dosage they recommend is far too high, if you
are also megadosing Vitamin C.

The following text has been extracted from:

http://www.nat-med.com/archives/quercetin.htm

Begin Extract:
Who is likely to be deficient? No clear deficiency of quercetin has been
established.

How much is usually taken? Common supplemental intake of quercetin
is 400 mg two to three times per day.

Are there any side effects or interactions? No clear toxicity has been identified.

Early quercetin research suggested that large amounts of quercetin could cause
cancer in animals.2 Most, 3 4 5 but not all,6 current research finds quercetin to
be safe or actually linked to protection from cancer.

Since flavonoids help protect and potentiate vitamin C, quercetin is often taken
with vitamin C.

Certain medications may interact with quercetin. Refer to the drug interactions
summary for a list of those medications. It is recommended you discuss the use
of quercetin and your current medication(s) with your doctor or pharmacist.

End Extract

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This is an advertisement for a particular supplement.
It doesn't say how much Vitamin C, or quercetin, so
it may be the Vitamin C is too low so they recommend
high doses of Quercetin. They do say that quercetin
is "activated" by Bromelain, Vitamin C and Magnesium.

The following extract is taken from:

http://www.horizonnutra.com/bioactive.html

Begin Extract:
Horizon Nutraceuticals
BioactiveQuercetin

Bioactive Quercetin™ is the most potent
supplemental source of Quercetin, a unique
bioflavonoid derived from plant sources.
Bioflavonoids are the natural pigments in
leaves, barks, rinds, seeds, flowers, fruits and
vegetables, found through extensive research
to be important to the optimal health of
humans. Quercetin is particularly well known
for its ability to help seasonally sensitive
individuals enjoy nature all year long.
Quercetin is "activated" by three key
substances: Bromelain (a proteolytic enzyme
derived from pineapple), Vitamin C, and
Magnesium. Vitamin C and Magnesium are
provided in Bioactive Quercetin magnesium in
the form of magnesium ascorbate, to help
neutralize C's acidity and enhance the
absorption of C, Magnesium and Quercetin.
Recommended Use: 3 to 6 tablets daily in
divided doses, between meals. If you have a
delicate, easily irritated stomach, take with
meals, or as advised by your health care
professional.

End Extract

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This article gives another tantalizing clue:

"Synergistic effects were present in.....as well as in all combinations of
vitamin C plus phenolic antioxidants". (quote from article below)
This relates to the anti-oxidant properties of Quercetin, but
suggests to me that in general the combination of vitamin C and quercetin
is synergistic.

Extract comes from Medline

J Agric Food Chem 2000 Jun;48(6):2266-70
Individual and combined antioxidant effects of seven phenolic agents in
human erythrocyte membrane ghosts and phosphatidylcholine liposome
systems: importance of the partition coefficient.

Liao K, Yin M

Institute of Nutritional Science, Chungshan Medical & Dental College,
Taichung, Taiwan, R.O.C.

Antioxidant activities of seven phenolic agents against Fe(2+)-induced
lipid oxidation were compared with alpha-tocopherol, beta-carotene, and
vitamin C in human erythrocyte membrane ghosts and liposome systems.
The antioxidant activity of five test flavonoids followed the order
catechin > epicatechin > rutin > quercetin > myricetin in both systems
(p < 0.05), which was negatively correlated with their partition coefficients.

The antioxidant interaction of these phenolic agents with alpha-tocopherol,
beta-carotene, or vitamin C in inhibiting Fe(2+)-induced lipid oxidation was
examined. Synergistic effects were present in the combinations of
alpha-tocopherol plus caffeic acid, catechin, or epicatechin as well as in all
combinations of vitamin C plus phenolic antioxidants. On the basis of the
stronger individual and combined effects present in caffeic acid, catechin,
and epicatechin, the application of these three phenolic agents with or
without alpha-tocopherol, beta-carotene, and vitamin C may provide
stronger protective benefits against lipid oxidation, which may be helpful
for oxidation-related diseases prevention.

PMID: 10888534, UI: 20347776

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The following article gives some background information, but appears to be the
result of not realizing the absorption resulting from high Vitamin C. Note dosage
recommendations! I already know from experience that this would give me quite
nasty side-effects. Also note the "Side Effects/drug interactions" section. This
is comforting, but it may not be true if you're using high Vitamin C. I think if you
keep the dose of Quercetin low, you're O.K. The article mentions the fact that
absorption from onions is fairly good. I suspect that onions may also be high
in Vitamin C. I will try to research this.
The following extract comes from:

http://www.nat-med.com/archives/quercetin.htm

Begin Extract
Quercetin: A Review of Clinical Applications

By L. Stephen Coles, M.D., Ph.D.

Los Angeles Gerontology Research Group

Introduction

Quercetin (3,3',4',5-7-pentahydroxyflavone), a chemical cousin of the glycoside
rutin, is a unique flavonoid that has been extensively studied by researchers
around the world, starting with the discovery of both vitamin C and flavonoids
by Albert Szent-Gyorgyi who received the Nobel Price in 1937 for research in this
area. Flavonoids, by the way, are plant polyphenolics found as the pigments in
leaves, barks, rinds, seeds, and flowers-frequently closely associated with
Vitamin C and offering synergistic effects. Both flavonoids and Vitamin C benefit
plants by providing them with antioxidant protection and also confer protection
against climatic variations (in wind, rainfall, temperature, and sunlight).
Flavonoids are also important for human health. Like vitamins, these compounds
are not produced endogenously by the body and must be supplied either through
the diet or nutritional supplements. Quercetin has been the subject of dozens of
scientific reports over the past 30 years. It has shown the greatest activity among
the flavonoids studied in experimental models. Quercetin is frequently used
therapeutically in allergic conditions, including asthma and hayfever, eczema, and
hives. Additional clinical uses include treatment of gout, pancreatitis and prostatitis,
which are also, in part, inflammatory conditions. The common link is its ability to
mediate production and manufacture of pro-inflammatory compounds.

However, its uses also may be important in cancer therapeutics. Quercetin is a
recognized antioxidant and has been studied for its gastro-protective effects,
inhibition of carcinogenicity either alone or in combination with chemotherapeutic
agents, reducing risk of cataract. Again, the ability of quercetin to inhibit
inflammatory leukotriene production may be a key to its beneficial impacts.
Sources of quercetin include green vegetables, berries, onions, parsley, legumes,
green tea, citrus fruits, and red grape wines.
.
.
.
Absorption
It is known that oral doses of quercetin are absorbed. In one study, plasma
quercetin concentration in subjects with an intact colon, after ingestion
of fried onions, apples, and pure quercetin rutinoside, decreased slowly
with an elimination half-life of about 25 hours. Thus, repeated dietary intake of
quercetin will lead to accumulation in plasma. The relative bioavailability of
quercetin from apples and rutinoside was one-third of that from onions.
Dietary quercetin would appear to increase the antioxidant capacity of blood
plasma. It is also thought that the combination of the proteolytic enzyme
bromelain with quercetin enhances absorption and bioavailability of quercetin.
.
.
.

Dosages
Most dosages range from 200 to 500 mg, taken 20 minutes before meals.
§ Asthma and Hay Fever: Take 400 mg 20 minutes before each meal.
§ Canker Sores: Take 400 mg 20 minutes before each meal.
§ Eczema: Take 400 mg 20 minutes before each meal.
§ Gout: Take 200 to 400 mg of quercetin with bromelain between meals
three times daily.
§ Hives: Take [200 - 400] mg 20 minutes before each meal.
A new water-soluble form of quercetin may be able to reduce dosages to
250- mg three times a day.
Side-effects/Drug Interactions
There are no known drug interactions. No long-term adverse effects from
the use of quercetin are noted in the medical literature.

End Extract

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Once again, the following article is at odds with my experience, probably
due to my use of high dosage Vitamin C. I suspect that if they are not
using Vitamin C, they may be getting very little absorption. Note the
first paragraph about anti-viral activity of flavonoids.
The following extract is taken from:

http://www.healthywave.com/ingredients/quercetin.html

Begin Extract
.
.

Although all flavonoids possess antiviral activity, studies have shown
that quercetin has the strongest antiviral activity. Quercetin protects
against the common cold and has antiviral activity against polio virus,
herpes virus type I, Coxasackie viruses, ECHO viruses, and respiratory
syncytial virus (Murray, 1996; Kirschmann, 1996)
.
.
.

SAFETY ISSUES

There are no known toxicities or adverse reactions for flavonoids, including
quercetin (Lieberman, 1997). Quercetin is well-tolerated in humans. Animal
studies have shown that even large quantities (2,000 milligrams per kilogram
of body weight and 5 to 10 percent of the total diet) for long periods of time
(up to 2 years) produce no adverse side effects. Administration of up to
2,000 milligrams per kilogram of body weight in pregnant rats had no
teratogenic effects. If an extremely rare allergic reaction should
occur, the supplement should be discontinued (Murray, 1996).

End Extract

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Yet another site to read about Quercetin:

http://www.thorne.com/altmedrev/fulltext/flavonoids1-2.html

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