Category: Natural chemicals
Introduction and description
Quercetin is a flavonol found in many fruits, vegetables, leaves and grains. The name has been used since 1857, and is derived from quercetum (oak forest), after Quercus. It is pale-yellow in colour and was first isolated from an oak (Quercus) but is widely distributed in nature. A weak acid, it combines with strong acids to form orange salts, which are not very stable and readily dissociate in water. Quercitin is a strong dyestuff; it yields more than one colour, depending on the mordant used.
It is one of the most abundant dietary flavonoids with [according to Wikipedia ] “an average daily consumption via various foods of 25–50 mgs”.
This means that those who sell supplements of Quercetin claiming various health benefits are not being entirely honest. The health benefits are real, as we shall see shortly, but people have no need of supplements, when something is this easy to obtain via good food. We have provided Dr Duke’s analysis of the foods which contain Quercetin to provide you with a list.
This said, the following is [if you will excuse the pun] food for thought:
Understanding how environment, crop management, and other factors, particularly soil fertility, influence the composition and quality of food crops is necessary for the production of high-quality nutritious foods. The flavonoid aglycones quercetin and kaempferol were measured in dried tomato samples (Lycopersicon esculentum L. cv. Halley 3155) that had been archived over the period from 1994 to 2004 from the Long-Term Research on Agricultural Systems project (LTRAS) at the University of California-Davis, which began in 1993. Conventional and organic processing tomato production systems are part of the set of systems compared at LTRAS. Comparisons of analyses of archived samples from conventional and organic production systems demonstrated statistically higher levels (P < 0.05) of quercetin and kaempferol aglycones in organic tomatoes. Ten-year mean levels of quercetin and kaempferol in organic tomatoes [115.5 and 63.3 mg g(-1) of dry matter (DM)] were 79 and 97% higher than those in conventional tomatoes (64.6 and 32.06 mg g(-1) of DM), respectively. The levels of flavonoids increased over time in samples from organic treatments, whereas the levels of flavonoids did not vary significantly in conventional treatments. This increase corresponds not only with increasing amounts of soil organic matter accumulating in organic plots but also with reduced manure application rates once soils in the organic systems had reached equilibrium levels of organic matter. Well-quantified changes in tomato nutrients over years in organic farming systems have not been reported previously. PMID: 17590007
Let me repeat these figures
“quercetin and kaempferol in organic tomatoes were 79% and 97% higher than those in conventional tomatoes”,
in other words eating tomatoes produced by factory farming is a pointless activity, as you are eating a nutritionally worthless product.
Activities of Quercetin
What biological activities does Quercetin possess?
Quercetin is contraindicated with some antibiotics; it may interact with fluoroquinolones (an antibiotic), as quercetin competitively binds to bacterial DNA gyrase. Whether this inhibits or enhances the effect of fluoroquinolones is not certain. AHFS Drug Information (2010 identifies quercetin as an inhibitor of CYP2C8, and specifically names it as a drug with potential to have harmful interactions with taxol/paclitaxel. As paclitaxel is metabolized primarily by CYP2C8, its bioavailability may be increased unpredictably, potentially leading to harmful side-effects.
which says more about the dangers of antibiotics than it does about Quercetin.
Since it ‘competitively binds to bacterial DNA' we can assume it probably has its own antibacterial activity – so a natural antibiotic. And we will see that this hypothesis is correct when we look at Dr Duke’s analysis.
A glance down the list of activities identified by Dr Duke from his research [and those of others] shows that Quercetin has some interesting healing effects. It is a pain killer and anti-inflammatory. It is an antiviral of some potency – flu, herpes, polio, HIV etc. It is, as is suggested above, an antibacterial, again of some potency.
It appears to have selected anti-parasitic activity – antimalarial and antileishmania being mentioned. It can even help with dental caries [from the antibacterial properties].
It is a natural antidepressant.
There are actions against pancreatic disease and liver disease, skin diseases, heart disease and blood circulatory system problems. It can help with prostate problems, stomach problems including ulcers,
It has some impressive anti-tumour activity.
It is a fungicide, again of some potency as it has action against candida.
At overdose levels – the sort of levels found in supplements – it is carcinogenic.
Dr Duke’s list of Biological Activities of QUERCETIN
Carcinogenic; 40,000 ppm (diet) mus;
The sinister side of science
Researchers have recognised that Quercetin is a very useful and healing natural chemical. All the activities identified by Dr Duke in the list above were obtained by plant researchers experimenting to see what the chemical is capable of. From what one can ascertain the majority of its activity is achieved via its anti-bacterial, anti-fungal, anti-parasitic and anti-viral properties. All these are CAUSES of illness and as such depending on which bacteria, which fungi, which parasites and which viruses it is able to combat it will, by definition, have extensive healing capabilities. But of course an illness can have more than one cause, as such for some it may heal for others with apparently the same disease it may not – simply because the cause is different and the chemical does not address every pathogen.
This has not stopped those with money making goals from ignoring the causes of illness altogether and pursuing the chemical as though it was yet another pharmaceutical – a prolongation of the old failed symptom based approach to illness.
Although quercetin is under basic and early-stage clinical research for a variety of disease conditions, there exists no evidence that it has any beneficial effect on DNA repair, liver and kidney systems, mental performance or cardiovascular health in the human body. The US FDA has issued warning letters, e.g., to emphasize that quercetin is …..not regulated as a drug to treat any human disease.
Let us now look at an example research paper based on the old symptom based model of medicine [no healing involved, simply sympton suppression] and contributed by those looking for pharmaceuticals to sell: First the good news:
Flavonoids are plant polyphenolic compounds present in the daily diet. Latest epidemiological studies point to a crucial role of the flavonol quercetin in the prevention of cardiovascular diseases. It is assumed that this protective effect derives from the antioxidative capacity which quercetin shows in in vitro experiments. The antiproliferative and antimutagenic activities in vitro have made it a candidate for clinical trials in cancer therapy. Quercetin is also regarded as a putative active compound in various phytopharmaceuticals. PMID: 10363620
‘It is assumed’ – wonderful science eh? So they don’t know why it is so good, nor have they bothered to find out, all they know is that they want to sell it – a ‘phytopharmaceutical’.
Remember that to get the benefits of Quercetin, all you have to do is eat it in foods – inexpensive, pleasurable and at the right dose. But here we have the chemist in full flood.......
The pharmacokinetic parameters following intravenous injection were determined in two studies. The elimination half-life was reported to be 2.4 h and 0.7 h, the volume of distribution at steady-state was 92.6 l and 6.2 l, and total body clearance was 34.6 lxh(-1) and 28.1 lxh(-1), respectively. PMID: 10363620
If you inject a substance into the blood stream and your body’s immune system is working effectively, it will fight that substance and build up an immunological record. By injecting somebody with Quercetin you will give them an allergy to quercetin containing foods – something of a disaster. I wish researchers would try out their experiments on each other for a change and leave the rest of us in peace.
- Dr Duke's list of Chemicals and their Biological Activities in: Morus alba L. (Moraceae) -- Sang-Pai-Pi, White Mulberry 027433
- Dr Duke's list of chemicals having anti-malarial activity 018059
- Dr Duke's list of Chemicals with Antiaflatoxin Activity 019138
- Dr Duke's list of chemicals with AntiHIV activity 017977
- Dr Duke's list of Chemicals with Tyrosine-kinase-inhibitor Activity 018251
- Dr Duke's list of Plants Containing QUERCETIN 021446
- Dr Duke’s list of Chemicals with Antiescherichic activity 021244
- Effects of dietary polyphenols on metabolic syndrome features in humans: a systematic review 021219
- Pharmacological safety evaluation of a traditional herbal medicine "Zereshk-e-Saghir" and assessment of its hepatoprotective effects on carbon tetrachloride induced hepatic damage in rats 027503
- Prevention and treatment of alopecia areata with quercetin 027899