Views: 0 Author: Site Editor Publish Time: 2023-04-10 Origin: Site
Quercetin is widely found in the stem bark, flowers, leaves, buds, seeds and fruits of many plants, mostly in the form of glycosides, such as rutin, quercitrin, hyperoside, etc. Quercetin can be obtained by acid hydrolysis. Among them, the content is higher in the rods and leaves of buckwheat, sea buckthorn, hawthorn, and onion. Quercetin is also found in many foods such as onions, shallots, asparagus, cabbage, mustard greens, green peppers, chicory, grapefruit, lettuce, hawthorn, apples, mangoes, plums, radishes, black currants, potatoes, and spinach. In addition, there are about 100 kinds of medicinal plants (such as Sophora japonica, Arborvitae leaves, Galangal, Coltsfoot, Sangji, Panax notoginseng, Ginkgo, Elderberry, etc.) contain this ingredient.
The research on the content of quercetin in tea, fruit juice and wine shows that the content of quercetin in some drinks (such as beer, coffee, chocolate milk, Baijiu) is below 1 mg/L, while the content of quercetin in red wine is 4-16 mg/L, and that in grape juice is 7-9 mg/L; In fruit juice, except for lemon juice (7 mg/L) and tomato juice (13 mg/L) with higher quercetin content, other fruit juices have lower content, generally below 5 mg/L; The highest content of quercetin in tea is 10-25 mg/L.
The preparation methods of quercetin include extraction and separation, acid hydrolysis, and enzymatic conversion, among which enzymatic conversion is the most practical.
1. Natural extraction and separation
Since the content of quercetin in plants is only a few thousandths to a few ten thousandths, and the extraction and separation are difficult and the cost is high, it is not practical to directly extract quercetin from plants. However, when analyzing and identifying flavonoids or preparing analytically pure samples, quercetin extraction and separation technology should be used.
2. Acid hydrolysis
The rutin (rutin) of quercetin is widely distributed in nature, and its content is high, such as the content in Sophora japonica is as high as 20%. It is feasible to extract rutin from Sophora japonica first, and then produce quercetin after acid hydrolysis.
The extraction methods of rutin mainly include alkali extraction and acid precipitation method, organic solvent extraction method and dipping method, among which the alkali extraction and acid precipitation method is the most practical. Select a 0.05% NaOH solution to boil for 20 minutes, filter while hot, and extract 4 times using the same method to obtain an alkaline aqueous solution of rutin. Add acid to precipitate it, filter, and then add acid to hydrolyze it to obtain insoluble quercetin. Filter, wash with water, and dry to obtain a solid quercetin.
3. Enzyme conversion method
Enzymatic hydrolysis of rutin is used to prepare a large amount of quercetin monomers with low content in plants. The operation is simple and safe, the entire process is economical and applicable, the yield is large, and it is suitable for industrial production. The purity of the product is>90%, which can meet the needs of food and clinical applications. Therefore, enzymatic conversion is undoubtedly a promising preparation method.
As the most common flavonoid compound, quercetin has a variety of biological activities, can resist oxidation, and plays an important role in the clinical treatment of cancer and cardiovascular diseases.
1. Antioxidant function
Quercetin not only participates in anti-oxidation in vitro, can inhibit DNA oxidative damage, but also protects tissues from oxidative damage in vivo by reducing the concentration of peroxides in tissues.
2. Anticancer effect
On the one hand, quercetin can effectively inhibit the production of free radicals. Its flavonoids such as quercetin 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 action of anticancer drugs and significantly improve the efficacy of the drugs.
3. Cardiovascular protection
The third major effect of quercetin is to protect the cardiovascular system. Mainly reflected in five aspects:
Dilate blood vessels, lower blood pressure;
Prevention and treatment of coronary heart disease: Through animal experiments, the function of reducing the incidence and mortality of myocardial infarction and blood sugar has also been found;
Reduce cardiac hypertrophy;
Inhibit hypertrophy of vascular smooth muscle cells;
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.
Several studies have shown that quercetin has an inhibitory effect on the inflammatory response induced by LPS.
Antibacterial effect: Quercetin is also a broad-spectrum antibacterial substance, which can be used to prevent and treat various bacterial infectious diseases.
Anti viral effect: Quercetin can fight against various viruses, such as HIV, anti sarcoma virus, human herpes simplex virus, parainfluenza virus type 3 (Pf-3), respiratory syncytial virus (RSV).
1. Antioxidant. It is mainly used in oils, beverages, cold drinks, and processed meat products.
2. It has good effects of eliminating phlegm, relieving cough and relieving asthma. It is used to treat chronic bronchitis, and also has auxiliary therapeutic effect on patients with coronary heart disease and hypertension.