Quercetin can fight cancer, why is it a three-type carcinogen?

Quercetin is in yellow color and It is insoluble in water and has a bitter taste. Quercetin is widely found in nature, and its English name “quercetin” reveals that it was originally derived from a plant – oak tree (English name: quercetum)

Sources of Quercetin

Quercetin is abundant in tea, apples, onions, tomatoes, broccoli and many other foods. In plants, quercetin exerts a natural inhibitory effect on auxin transport, which is extremely important for the normal growth and development of plants. Quercetin is an aglycone (component) of many other flavonoid glycosides, for example, quercetin combines with rhamnose to form quercitrin, rutose to form rutin, arabinose to form guavaside, and Lactose combines to form hypericin and the like.

How about the benefits of Quercetin?

Quercetin is generally used as a health supplement and is often used to increase immunity or prevent infection. Quercetin has a variety of effects, has good expectorant, antitussive effect, and has a certain antiasthmatic effect for the treatment of chronic bronchitis. In addition, it has the functions of lowering blood pressure, enhancing capillary resistance, reducing capillary fragility, lowering blood lipids, expanding coronary arteries, and increasing coronary blood flow. It also has adjuvant therapy for patients with coronary heart disease and hypertension. Our daily intake of vegetables and fruits is rich in bioflavonoids, most of which are quercetin, which shows the importance of these compounds in the human diet.

In terms of anti-cancer, many studies have shown that quercetin has an inhibitory effect on various cancer cells. As far as the specific mechanism of action is concerned, quercetin has a variety of biological effects, inhibiting various enzymes in cancer cells involved in cell proliferation and signal transduction pathways.

Low-dose quercetin exerts a cancer cell-specific proliferation inhibitory effect, which is caused by cell cycle arrest in the G1 phase. Quercetin-induced p21 CDK inhibitor was accompanied by a decrease in phosphorylation of pRb, which inhibits G1/S cell cycle progression by trapping E2F1. Low doses of quercetin induce mild DNA damage and activation of Chk2, which are master regulators of p21 expression by quercetin. In addition, quercetin downregulates cyclin B1 and CDK1, which are important components of G2/M cell cycle progression. Inhibition of the recruitment of the key transcription factor NF-Y to the cyclin B1 gene promoter by quercetin results in transcriptional repression. This study demonstrates that the chemopreventive efficacy of quercetin at physiologically relevant doses can be achieved by inhibiting cell cycle progression.

On the other hand, there are also studies showing that the use of quercetin in combination with common chemotherapeutic agents or radiotherapy has a certain synergistic effect and has certain application prospects. For example, quercetin can act on chemosensitizing and radiosensitizing chemotherapy and also act as anti-radiation, protecting normal cells from the side effects of chemotherapy and radiotherapy, these advantages can significantly enhance its anti-cancer therapeutic effect.

However, in the list of carcinogens published by the International Agency for Research on Cancer of the World Health Organization in October last year, quercetin, an extract of oak tree, was included in the list of three types of carcinogens. In fact, class 3 carcinogens have a different meaning than what we usually understand as carcinogens. Category 3 carcinogens refer to the fact that the available evidence cannot confirm human carcinogenicity, that is, the evidence of carcinogenicity is insufficient. For example, tea, caffeine, saccharin and its salts, diazepam, iron oxide, organic lead compounds, electrostatic magnetic fields, melamine, mercury and its inorganic compounds are all class 3 carcinogens. Compounds with carcinogenic potential.

Therefore, although quercetin is listed in the list of 3 types of carcinogens, it is still uncertain whether it has carcinogenic potential. Quercetin has many functions such as antioxidant, scavenging free radicals, and inhibiting lipid peroxidation. It can resist oxidation, protect cardiovascular health, and also shows good effects in anti-cancer. However, such research data are all from cytological experiments or animal experiments, and whether it will work directly in humans remains to be more verified. The author does not recommend the use of quercetin health products, because it is different from other health products, quercetin and its analogs can be adequately ingested through vegetables and fruits.

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