ABSTRACT
Water extract from commercial English tea has a potent inhibitory activity against human placenta aldose reductase (NADPH oxidoreductase, E.C.1.1.1.21.). Inhibitory activity was separated into five major fractions by one-step chromatography with a C-18 reverse phase column. The most active fraction was further subjected to reverse phase column chromatography. As a result, a well-known flavone-glycoside, isoquercitrin, was isolated as the most potent chemical. The inhibitory character of isoquercitrin for aldose reductase was a mix of uncompetitive and noncompetitive inhibitions, and its IC50 was 1 x 10(-6) M. In rat sciatic nerve tissue preparations, sorbitol accumulation in the presence of high concentrations of glucose (30 mM) was inhibited by 38% at 5 x 10(-4) M of isoquercitrin. The flavone-glycoside isoquercitrin is the active inhibitor of aldose reductase inhibitor present in English tea. Given the ability of aldose reductase inhibitors to prevent diabetic complications, an epidemiological study of the effect of tea consumption on the pathogenesis and progression of diabetic complications would be interesting.
Subject(s)
Aldehyde Reductase/antagonists & inhibitors , Enzyme Inhibitors/pharmacology , Quercetin/pharmacology , Tea/chemistry , Aldehyde Reductase/metabolism , Animals , Binding Sites , Enzyme Inhibitors/isolation & purification , Enzyme Inhibitors/metabolism , Female , Humans , In Vitro Techniques , Placenta/enzymology , Plant Extracts/metabolism , Plant Extracts/pharmacology , Quercetin/analogs & derivatives , Quercetin/isolation & purification , Rats , Sciatic Nerve/metabolism , Sorbitol/metabolismABSTRACT
Recently, endoscopic treatments have been applied for the curative treatment of early gastrointestinal cancers and for the palliative treatment of end-stage gastrointestinal cancers. As a curative treatment for early gastric cancers, the endoscopic Nd-YAG laser therapy was initially applied and a satisfactory results were obtained. However, the endoscopic mucosal resection (EMR) is evaluated as the reliable endoscopic treatment for early gastric cancers because curability can be histologically detected by resected specimen. EMR technique is also applied for early esophageal cancers and early flat or depressed colon cancers. EMR-L (EMR with the use of Ligating device) developed by us is mainly practiced in our department. By the use of EMR-L technique. Resectability has been improved compared with 2 channel EMR technique. As the palliation of end-stage gastrointestinal cancers endoscopy recanalization of malignant esophageal stenosis is very effective to improve the patient's QOL. The memorial metallic stent for esophageal stenosis is very useful to keep cavity for a long term after endoscopic recanalization. PEG (percutaneous endoscopic gastrostomy) is also very effective to reduce the symptoms of the patients with peritonitis carcinoma or ileus. In this paper, the present status of curative and palliative endoscopic treatment for gastrointestinal cancers was reported. In recent future, endoscopy will be more widely applied as a less invasive therapeutic procedure for gastrointestinal cancers.
