Quercetin

Quercetin Uses and Synthesis Methods
Expectorant
Quercetin is a commonly used expectorant in Chinese medicine. It has good expectorant and antitussive effects, as well as certain antiasthmatic effects. It also has the pharmacological functions of lowering blood pressure, improving capillary resistance, reducing capillary fragility, lowering blood lipids, dilating coronary arteries, and increasing coronary blood flow.
Clinically, quercetin is mainly used for bronchitis and phlegm inflammation. It also has an auxiliary therapeutic effect on patients with coronary heart disease and hypertension. The use of this product may cause dry mouth, dizziness, and burning sensation in the stomach area, which disappears after stopping the drug.
Quercetin is widely present in angiosperms, such as red tube medicine, cat's eye grass, iron-wrapped gold, red mountain, small-leaf loquat, purple flower azalea, Zhaoshanbai, dwarf tea, and Luobu Ma. This substance is a kind of aglycone, which is often combined with sugar in the form of glycosides, such as quercetin, rutin, hyperoside, etc.
Plant sources
Quercetin is a flavonol compound with a wide distribution in the plant kingdom and multiple biological activities. It exists in a variety of vegetables and fruits, such as acai berries, broccoli and apples, and also in foods such as tea, red wine, olive oil and propolis. Among them, the content is higher in Sophora japonica, buckwheat stems and leaves, sea buckthorn, hawthorn and onion.
Quercetin mainly comes from plants such as acerola, tea, red onion, raspberry, and bilberry.

The content of quercetin in some vegetables and fruits in the American Flavonoid Database.
Pharmacological effects
Quercetin can significantly inhibit the effects of cancer promoters, inhibit the growth of malignant cells in vitro, and inhibit the DNA, RNA and protein synthesis of Ehrlich ascites carcinoma cells.
Quercetin has the effect of inhibiting platelet aggregation and the release of 5-hydroxytryptamine (5-HT). It has a significant inhibitory effect on platelet aggregation induced by ADP, thrombin and platelet activating factor (PAF). Among them, the inhibitory effect on PAF is the strongest. It can also significantly inhibit the release of 3H-5-HT from rabbit platelets induced by thrombin.
(1) Intravenous drip of 0.5mmol/L quercetin at a concentration of 10ml/kg can significantly shorten the duration of arrhythmia in mice with myocardial ischemia-reperfusion, reduce the incidence of ventricular fibrillation, reduce the MDA content and xanthine oxidase activity in the myocardial tissue of the ischemic perfusion area, and have a significant protective effect on SOD, which may be related to inhibiting the formation of oxygen free radicals in the myocardium and protecting SOD in the myocardial tissue or directly scavenging oxygen free radicals.
(2) In vitro tests, quercetin and rutin can disperse platelet thrombi adhered to the rabbit aortic endothelium, with EC50 of 80 and 500nmol/L respectively. In vitro tests of quercetin at 50-500 μmol/L showed that it could increase the cAMP level of human platelets, increase the cAMP level of human platelets and inhibit ADP-induced human platelet aggregation. Quercetin at 2-50 μmol/L had a concentration-dependent enhancement effect on PGI2. Quercetin at a concentration of 300 μmol/L in vitro almost completely inhibited platelet aggregation induced by platelet activating factor (PAF) in rats, and also inhibited thrombin and ADP-induced platelet aggregation, and had an inhibitory effect on the release of 3H-5HT from rabbit platelets induced by thrombin; a concentration of 30 μmol/L could significantly reduce the membrane fluidity of rat platelets.
(3) Quercetin at a concentration of 4×10-5-1×10-1 g/ml inhibited the release of histamine and SRS-A from the lungs of guinea pigs sensitized to ovalbumin; 1×10-5 g/ml also inhibited the contraction of the guinea pig ileum induced by SRS-A. Quercetin at a concentration of 5 to 50 μmol/L has a concentration-dependent inhibitory effect on the release of histamine from human basophils induced by ragweed antigens. It has a concentration-dependent inhibitory effect on the contraction of the ileum of guinea pigs sensitized to ovalbumin, with an IC50 of 10 μmol/L. 5×10-6 to 5×10-5 mol/L can inhibit the proliferation of mouse cytotoxic T lymphocytes (CTL) and also inhibit ConA-induced DNA synthesis.
Efficacy and Function
As the most common flavonoid compound, quercetin has a variety of biological activities and can resist oxidation, playing an important role in the clinical treatment of cancer and cardiovascular diseases.
Antioxidant Function
Quercetin not only participates in in vitro antioxidant activity and can inhibit DNA oxidative damage, but also protects tissues from oxidative damage in vivo by reducing the concentration of peroxides in tissues.
Anticancer Effect
On the one hand, quercetin can effectively inhibit the production of free radicals. The flavonoid components such as quercetin it contains can significantly reduce the incidence of gastric cancer, directly inhibit the growth of cancer cells or may act on the cell transduction pathway of cancer cell proliferation.
On the other hand, it can enhance the effect of anticancer drugs and significantly improve the efficacy of drugs.
Protect cardiovascular system
The third major effect of quercetin is to protect cardiovascular system. It is mainly reflected in five aspects:
Dilation of blood vessels and lowering blood pressure;
Prevention and treatment of coronary heart disease: Through animal experiments, it has also been found that it can reduce the incidence and mortality of myocardial infarction and lower blood sugar;
Reducing myocardial hypertrophy;
Inhibiting the proliferation and hypertrophy of vascular smooth muscle cells;
Anti-thrombosis.
In addition, quercetin also has neuroprotective, anti-inflammatory and antiviral effects.
Anti-inflammatory effect: When the human immune system fights against bacterial invasion, lipopolysaccharide (LPS) can cause the body's immune response and inflammatory response. Some studies have shown that quercetin has an inhibitory effect on the inflammatory response caused by LPS.
Antibacterial effect: Quercetin is also a broad-spectrum antibacterial substance that can be used to prevent and treat various bacterial infectious diseases.
Antiviral effect: Quercetin can fight against many viruses, such as HIV, anti-sarcoma virus, human herpes simplex virus, parainfluenza virus type 3 (Pf-3), respiratory syncytial virus (RSV).
Preparation
Quercetin and its derivatives are widely found in various vegetables and fruits. They can be obtained from onions of the Liliaceae family and other plant extracts such as rutin, quercetin, isoquercetin, fennel glycosides, quercetin, and calycin. It can also be prepared by hydrolysis of rutin. The synthetic reaction formula of quercetin is as follows:

Figure 1 Synthetic reaction formula of quercetin

Experimental operation:

Method 1.

Accurately weigh 4.00g (about 2.69mmol) of refined rutin and place it in a 500mL round-bottom flask, add 400mL of 2% dilute sulfuric acid, react at 80-90℃ for 4h, track the reaction by TLC until the end of the reaction, let it stand for 4h, perform vacuum filtration, wash the filter cake with distilled water until it is neutral, and dry it to obtain THQ crude product. . The obtained crude product was recrystallized with 400mL of anhydrous ethanol to obtain 2.41g of yellow powder quercetin.

Method 2,

Ultrasonic-mechanical oscillation assisted extraction method

Accurately weigh about 0.4g of Guizhou Liping radix scutellariae leaf sample, put it in a 50ml stoppered centrifuge tube, add the extraction solvent of methanol: 6.5mol/L hydrochloric acid solution in a ratio of 4:1, add and mix at a solid-liquid ratio of 1:70, ultrasonic frequency 59Hz, ultrasonic power 100W, water bath temperature 65℃ for 40min, then oscillate and extract at room temperature for 30min, take it out, place it at room temperature, weigh it (use methanol to make up for the lost weight), shake it well, centrifuge it at 8000r/min for 10min, take the supernatant, filter it through a 0.2m filter membrane, and test it.

Chemical properties
Yellow needle-shaped crystalline powder. Stable to heat, decomposition temperature 314℃. It can improve the light resistance of pigments in food and prevent the change of food flavor. It will change color when it encounters metal ions. It is slightly soluble in water and easily soluble in alkaline aqueous solution. Quercetin and its derivatives are a class of flavonoid compounds widely found in various vegetables and fruits. Such as onion, sea buckthorn, hawthorn, sophora japonica, tea, etc. It has anti-free radical, anti-oxidation, antibacterial, anti-viral, anti-allergic and other effects. When used in lard, etc., various antioxidant indicators are similar to BHA or PG.

Because it has a double bond between the 2nd and 3rd positions, and two hydroxyl groups at the 3' and 4' positions, it has the function of being a free radical acceptor generated during metal chelation or oxidation of oils and fats, so it can be used as an antioxidant for ascorbic acid or oils. It has a diuretic effect.
Uses
Antioxidant. Mainly used in oils, beverages, cold drinks, and meat processing products.
Uses
It has good expectorant, antitussive, and antiasthmatic effects. It is used to treat chronic bronchitis and has an auxiliary therapeutic effect on patients with coronary heart disease and hypertension.
Uses
Analytical standard
Uses
A flavonoid compound with anticancer activity, an inhibitor of mitochondrial ATPase and phosphodiesterase, inhibits PI3 kinase activity and slightly inhibits PIP kinase activity, IC50: 3.8μM. It has anti-proliferative effects on cancer cell lines, reduces cancer cell growth through type II estrogen receptors, and blocks human leukemia T cells in the G1 late stage of the cell cycle. Inhibits fatty acid synthase activity.
Production method
Grind the bark of the Quercus plant of the Fagaceae family into powder, wash with hot salt water, extract with dilute ammonia water, and neutralize with dilute sulfuric acid. Boil the filtrate and precipitate crystals to obtain it.
It can be extracted from the onion (Alliumcepa) of the Liliaceae family with 95% ethanol; it can also be obtained by hydrolyzing rutin (rutin) extract and quercetin, isoquercetin, anise glycoside, hyperoside, quercetin, and calycin with rutin decomposition enzymes or acidic aqueous solutions.