Quercetin

Description

The name of quercetin has been used since 1857, which is derived from quercetum (oak forest) after Quercus. Quercetin is widely found in flowers, leaves, and fruits of various plants. Vegetables (such as onions, ginger, celery, etc.), fruits (such as apples, strawberries, etc.), beverages (such as tea, coffee, red wine, fruit juice, etc.), and more than 100 kinds of Chinese herbal medicines (such as Threevein Aster, mountain white chrysanthemum, Huai rice, Apocynum, Ginkgo biloba, etc.) contain this ingredient.
Threevein Aster is a Chinese herbal medicine and used in Jiangxi province, China, for more than 30 years. Its plant name is three veins Mala, Compositae. It is rich in drug sources, which can be found in Southern provinces of China. Clinical practice proved that it has significant anti-inflammatory and expectorant effects, and it is a good prescription for the treatment of elderly chronic bronchitis.

Chemical Properties

Yellow to green yellow crystalline powde

Physical properties

Appearance: yellow needle-like crystalline powder. Solubility: slightly soluble in water; soluble in ethanol, acetone, pyridine, and acetic acid; easily soluble in ether and methanol. Melting point: 314–317 °C.

History

In 1936, Szent-Gyorgyi firstly reported the separation and identification of biological activity of quercetin. Usually quercetin is presented in the form of glycosides such as lutin, quercitrin, and mycoside, which can be hydrolyzed to get the quercetin.
Quercetin has a polyphenol hydroxyl structure, which is of weak lipophilicity and poor hydrophilicity, resulting in its low bioavailability and limiting its clinical application. The synthesis of phenolic derivatives improves its bioavailability, which are lipid-soluble quercetin derivatives such as 3-O-methylquercetin, hydrophilic quercetin derivatives such as 3′-ON-carboxymethylformamide quercetin, and quercetin glycosides.
Threevein Aster, having quercetin as one of the main active ingredients, has been used for the domestic clinical treatment for chronic bronchitis in China since 1971.

Uses

• Quercetin has been used as an antioxidant which reversed the immunosuppressive effects of high glucose and hyperglycemic sera in type 2 diabetic patients.
• It has been used as a detoxifying phytochemical in Apis mellifera.
• It has been used as a positive control in DPPH (2,2- diphenyl-1-picryhydrazyl) radical scavenging assay. It has also been used for the preparation of calibration curve to determine total flavonoid content.

Indications

It is mainly used for the treatment of chronic bronchitis.

General Description

Yellow needles or yellow powder. Converts to anhydrous form at 203-207°F. Alcoholic solutions taste very bitter.

Air & Water Reactions

Sensitive to exposure to air and light. Insoluble in water.

Reactivity Profile

3,3',4',5,7-Pentahydroxyflavone is a strong antioxidant and a metal chelator. Promotes the formation of nitrosamines .

Hazard

Questionable carcinogen.

Health Hazard

ACUTE/CHRONIC HAZARDS: When heated to decomposition 3,3',4',5,7-Pentahydroxyflavone emits acrid smoke and irritating fumes.

Fire Hazard

Flash point data for 3,3',4',5,7-Pentahydroxyflavone are not available; however, 3,3',4',5,7-Pentahydroxyflavone is probably combustible.

Biological Activity

Anti-tumor agent; induces apoptosis and inhibits synthesis of heat shock proteins. Inhibits many enzyme systems including tyrosine protein kinase, phospholipase A 2 , phosphodiesterases, mitochondrial ATPase, PI 3-kinase and protein kinase C. Can also activate Ca 2+ and K + channels and behaves as an agonist at estrogen (GPR30) receptors.

Pharmacology

Experimental studies showed that quercetin had antitumor, anti-inflammatory, anti-oxidation, hypoglycemic, anti-obesity, antidepressant, and other effects. In vitro cell experiments and in vivo animal experiments have shown that quercetin could inhibit the growth of various malignant tumor cells such as human ovarian cancer, breast cancer, gastrointestinal tumor cells, and leukemia, and it could induce cancer cell apoptosis and had a reversal of tumor multidrug resistance (MDR) effect, while, combined with other anticancer drugs, it could enhance the effect of anticancer drugs.
Quercetin could alleviate the inflammatory response that was aggravated by the activation of the central granulocytes. In the experimental study on the treatment of non-bacterial prostatitis and acute gouty arthritis, quercetin also showed a good anti-inflammatory effect.
The experimental results showed that quercetin had a good direct scavenging effect on free radicals and exhibited antioxidant activity. In addition, it also had the anti-hepatic fibrosis, pulmonary fibrosis, keloid hyperplasia and glaucoma filtering bubble scarring and other effects, its mechanism involving the inhibition of fibroblast proliferation, inhibition of collagen synthesis, preventing oxidative damage and so on. Moreover, studies have shown that quercetin also had antibacterial, antiaging, antidepressant, antileukemia, antidiabetic, and other pharmacological effects.

Clinical Use

Since the first clinical phase I trial of quercetin in 1996 found that it had antitumor activity, quercetin has also been reported in early clinical trials of cardiovascular disease, diabetes, and other diseases. However, there is still insufficient evidence shown that quercetin has a significant effect on the treatment of the disease in clinic.The US FDA has issued a warning, emphasizing that quercetin is not a definite nutrient, unable to determine its content in the diet, nor can it be used as a drug.
China’s Threevein Aster consists of a single Chinese herb, which was released by the Pharmacopoeia of the People’s Republic of China (1977) Part I. One of the main active ingredients obtained following the hydrolysis of Threevein Aster is quercetin, which has the function of relieving cough and eliminating phlegm and can be used for the treatment of chronic bronchitis. The anti-inflammatory effect of Threevein Aster is poor. Side effects after use include stomach discomfort, dizziness, and abdominal pain, while withdrawal can make them disappear.

Safety Profile

Poison by ingestion, subcutaneous, and intravenous routes. Experimental teratogenic and reproductive effects. Questionable carcinogen with experimental carcinogenic, neoplastigenic, and tumorigenic data. Human mutation data reported. Used as a pharmaceutical and veterinary drug. When heated to decomposition it emits acrid smoke and irritating fumes