Interaction of magnolia bark extracts with Staphylococcus aureus DNA and evaluation of the stability of their antibacterial activities.

Magnolia bark is an edible traditional Chinese medicine that has antibacterial activity against Staphylococcus aureus. In the present study, interactions between S. aureus DNA and raw magnolia bark (RMB) and ginger mix-fried magnolia bark (GMB) aqueous extracts were determined via spectroscopic methods. Fluorescence spectroscopy and Stern-Volmer constants showed that S. aureus DNA quenched the fluorescence of the extracts by static quenching. UV-Vis spectroscopy and iodide quenching experiments indicated that the interactions between S. aureus DNA and the fluorescent substances might involve groove binding or electrostatic interactions. In 4', 6-diamidino-2-phenylindole competitive assays, the fluorescence intensity at decreased as the extract amount was increased. This indicates that groove binding is responsible for the fluorescence quenching. The antibacterial activity of GMB aqueous extract treated under light, cold, heat and cycling hot-cold conditions decreased by 13.99, 9.31, 10.89 and 14.40%, respectively, whereas that of RMB aqueous extract treated under the same conditions decreased by 8.91, 14.99, 14.99 and 13.70%, respectively. The results indicate that S. aureus DNA quenches the fluorescence of GMB and RMB aqueous extracts by grooving interactions. Additionally, the antibacterial activities of GMB and RMB extracts are sensitive to light and temperature, respectively.

CO2-Mediated Formation of Chiral Carbamates from meso-Epoxides via Polycarbonate Intermediates.

Carbon dioxide has attracted broad interest as a renewable C1 feedstock for efficient transformation into value-added organic chemicals; nevertheless, far less attention was paid to its stereochemically controlled catalytic fixation/conversion processes. Here, we report a new strategy for the selective synthesis of chiral carbamates from carbon dioxide via polycarbonate intermediates, which are formed by the desymmetric copolymerization of meso-epoxides using enantiopure dinuclear Co(III) catalyst systems with 99% enantioselectivity. Subsequent degradation reaction of the resultant polycarbonates with various primary or secondary amine nucleophiles can afford optically active carbamates, with the complete configuration retention of the two chiral carbon centers. Our accomplishment reported here opens up a new route to prepare a wide range of CO2-based carbamate scaffolds with excellent yields and 99% enantiomeric excess.

Crystalline-gradient polycarbonates prepared from enantioselective terpolymerization of meso-epoxides with CO2.

The development of efficient processes for CO2 transformation into useful products is a long-standing goal for chemists, since CO2 is an abundant, inexpensive and non-toxic renewable C1 resource. Here we describe the enantioselective copolymerization of 3,4-epoxytetrahydrofuran with CO2 mediated by biphenol-linked dinuclear cobalt complex, affording the corresponding polycarbonate with >99% carbonate linkages and excellent enantioselectivity (up to 99% enantiomeric excess). Notably, the resultant isotactic polycarbonate is a typical semicrystalline polymer, possessing a melting point of 271 °C. Furthermore, the enantioselective terpolymerization of 3,4-epoxytetrahydrofuran, cyclopentene oxide and CO2 mediated by this dinuclear cobalt complex gives novel gradient polycarbonates, in which the decrement of one component and the increment of the other component occur sequentially from one chain end to the other end. The resultant terpolymers show perfectly isotactic structure and have unique crystalline-gradient nature, in which the crystallinity continuously varies along the main chain.

[Transportal variceal sclerotherapy with n-butyl-2-cyanoacrylate for gastric fundal varices].

OBJECTIVE: To evaluate the technique, safety and clinical efficacy of transportal variceal sclerotherapy with n-butyl-2-cyanoacrylate (NBCA) for gastric fundal varices. METHODS: Twenty-one patients with gastric fundal varices confirmed by endoscopy were enrolled in this study. The causes of the gastric varices were cirrhosis caused by hepatitis virus B or C (n = 16) and hepatocellular carcinoma with portal venous obstruction (n = 5). Percutaneous transhepatic or transplenic portography were performed on all 21 patients. The gastric varices were treated with NBCA-lipiodol mixture injected via a microcatheter introduced into the varices. For 8 patients who had large gastrorenal shunts (GRS), a balloon-occluded catheter was introduced into the GRS via the right femoral and left renal veins before injecting the NBCA-lipiodol. During the NBCA-lipiodol injection, the balloon was inflated to block the flow of GRS. Follow-up evaluations included findings of the laboratory liver function tests, upper intestinal endoscopies, and the occurrences of rebleeding. RESULTS: In 20 patients (95.2%), the gastric varices were successfully obliterated with 2-8 ml of NBCA-lipiodol. In one patient with a large GRS, sclerotherapy was not successfully performed because a balloon-occluded catheter was not available during the procedure. In five patients, small amounts of NBCA-lipiodol entered into the distal pulmonary artery branches. Two of them suffered from transient irritable coughs; no patient developed severe pulmonary embolism. Embolization of portal venous branches occurred in two patients, which were not treated specifically. In comparison with the findings before the treatments, the serum alanine aminotransferase levels decreased at both 3 and 6 months after treatments (P less than 0.05); serum albumin levels increased at 6 months (P less than 0.05); the prothrombin times decreased at 6 months (P less than 0.05); but no significant changes were seen in the serum bilirubin levels. Fifteen patients were followed-up endoscopically for 3 months after the treatment. Gastric varices were completely resolved in 10 patients (66.7%) and were markedly smaller in 4 patients (26.6%). Worsening of the esophageal varices occurred in 3 patients (20%). All the patients were followed-up from 1 to 30 months [(16.7+/-8.8) months]. Rebleeding was observed in 4 patients, and the cumulative rebleeding rate at 1 year was 9.52%. CONCLUSION: Transportal variceal sclerotherapy with NBCA is a safe and effective method for treating gastric varices. Microcatheter technique and occlusion of the large gastrorenal shunt with a balloon-occluded catheter are necessary to ensure obliteration of gastric varices and prevent pulmonary embolism.

[The role of multi-detector row CT in the diagnosis and hemodynamic studies of gastric varices in portal hypertension].

OBJECTIVE: To evaluate the value of multi-detector row CT (MDCT) in the diagnosis and hemodynamic studies of gastric varices (GV) in portal hypertension by comparison with endoscopy and DSA direct portography. METHODS: Thirty-six consecutive cirrhotic patients with GV confirmed by endoscopy underwent tri-phase contrast-enhanced CT scans and CT portography (CTP) within 2 weeks after endoscopy examination. Three independent experienced radiologists, who were blinded to the patients' clinical data, analyzed the CT images, including the size and location of GV as well as afferent and efferent veins of GV, separately. Interobserver agreement among the 3 radiologists with regard to the diagnosis of submucosal and perigastric GV was determined by Kappa (k) values. The findings of endoscopy were used as standards. RESULTS: Sub mucosal GV was diagnosed in 34 of the 36 patients (94.4%) and perigastric GV in all 36 patients (100%) by the observation of the 3 radiologists. MDCT showed an excellent interobserver reliability with regard to the diagnosis of submucosal GV (kappa = 0.85) and perigastric GV (kappa = 1.0). Agreement between MDCT and endoscopy with regard to the opacification of variceal size and location were 86.1% and 88.9% respectively. The sensitivity, specificity, accuracy, and positive predictive value of CTP in the opacification of afferent and efferent veins of GV were all more than 80%. The frequencies of participation of posterior gastric vein and short gastric vein in blood supply to gastric fundal varices in the isolated gastric varices and gastroesophageal varices type 2 (GEV2) were 94.1% and 70.6% respectively, both significantly higher than those in the gastroesophageal varices type 1 (GEV1, 52.6% and 31.6%, respectively, both P < 0.05). The main blood drainage route of GEV1 was via azygous system into the super vena cava (100%), whereas in the gastric fundal varices the main blood drainage route was via the gastrorenal shunts into the inferior vena cava (82.4%). CONCLUSION: MDCT can be used as an important tool for detecting submucosal and perigastric GV, and can clearly reveal the size, location, and hemodynamics of GV.