ケルセチン

解説ケルセチン，黄色の針状晶で2分子の水和水を含む．95～97 ℃ で無水和物となる．分解点314 ℃．λmax 258，375 nm(log ε 2.75，2.75．エタノール)．pKa 6.89±0.60．熱エタノール，氷酢酸に易溶，冷エタノール，エーテルに難溶，冷水にはほとんど不溶．FeCl3で暗緑色を呈する．配糖体のおもなものにクエルシトリン(3-ラムノシド)，クワMorus albaの葉などにあるイソクエルシトリン(3-グルコシド)，ソバFagopyrum esticulentumの全草，サンシキスミレViola tricolorの花などに含まれるルチン(3-ラムノシルグルコシド)がある．森北出版「化学辞典（第2版）

説明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.

来歴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.

使用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.

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