Characterization of a D-mannitol oxidase from Paenibacillus sp. and its application in the preparation of D-mannose / 生物工程学报

D-mannose has many functional activities and is widely used in food, medicine, agriculture and other industries. D-mannitol oxidase that can efficiently convert D-mannitol into D-mannose has potential application in the enzymatic preparation of D-mannose. A D-mannitol oxidase (PsOX) was found from Paenibacillus sp. HGF5. The similarity between PsOX and the D-mannitol oxidase (AldO) from Streptomyces coelicolor was 50.94%. The molecular weight of PsOX was about 47.4 kDa. A recombinant expression plasmid pET-28a-PsOX was constructed and expressed in Escherichia coli BL21(DE3). The Km and kcat/Km values of PsOX for D-mannitol were 5.6 mmol/L and 0.68 L/(s·mmol). Further characterization of PsOX showed its optimal pH and temperature were 7.0 and 35 ℃, respectively, while its enzyme activity could be stably remained below 60 ℃. The molar conversion rate of 400 mmol/L D-mannitol by PsOX was 95.2%. The whole cells of PsOX and AldO were used to catalyze 73 g/L D-mannitol respectively. The reaction catalyzed by PsOX completed in 9 h and 70 g/L D-mannose was produced. PsOX showed a higher catalytic efficiency compared to that of AldO. PsOX may facilitate the enzymatic preparation of D-mannose as a novel D-mannose oxidase.

Genotoxicity assessment of three reference chemicals in rat hepatocytes by alkaline comet assay / 上海预防医学

Objective:To establish a comet test method for detection of genotoxicity of three reference chemicals in rat liver cells. Methods:6-10 week old Sprague Dawley rats were randomly divided into 4 groups， with normal saline （0.9% NaCl solution） as negative control group. Animals in three test groups were treated， respectively， with ethyl methanesulfonate （EMS） 200 mg/kg， N-methyl-N-nitrosourea （MNU） 50 mg/kg， and D-mannitol 2 000 mg/kg. There were 10 animals in each group， 5 males and 5 females. The animals received two times （21 h interval） of test compounds through intragastric administration， and their clinical symptoms and body weight changes were recorded during the experiment. The rats were sacrificed 3 h after the last exposure. The liver was weighed， then used to prepare single-cell suspensions for the alkaline comet test which determines the average tail DNA content percentage （DNA%） of hepatocytes and other comet indicators. Results:（1） D-mannitol， EMS and MNU did not show significant toxicity in the whole animal. （2） The mean values of tail DNA content percentage （DNA%） of rat hepatocytes in EMS ［（60.07±24.69）%］ and MNU ［（41.66±22.35）%］ groups were higher than that in the negative control group ［（2.32±1.39）%］ and the difference was statistically significant （P<0.05）. The difference between D-mannitol group ［（3.06±3.30）%］ and the negative control group was not significant （P>0.05）. Conclusion:This laboratory has established a comet test method using hepatocytes from treated rats. Among three testing chemicals， EMS and MNU have displayed genotoxicity by this assay， but no genotoxicity was observed in D-mannitol treated animals.

Gum Arabic Enhances Paracellular Transport of Water in Amphibian Everted Small Intestinal Segments.

Gum Arabic (GA) is known for its proabsorbent activity in normal intestine as well as in animal models of diarrhea. The aim of the study was to find the effect of GA on intestinal transport of water and possible route of absorption in frog everted gut sacs. D-Mannitol was used as a marker of paracellular transport to find the route of absorption. Everted gut sacs (n=4,5) were placed in Ringer containing GA (2.5 g/L) with or without D-Mannitol (0.5 g/L), incubated for 1 hour and analysed for change in weights of the sacs and D-Mannitol uptake. There was significant increase in uptake of water and D-Mannitol in the presence of GA compared to controls (P<0.05).Gum Arabic improves water uptake by the intestinal mucosa, possibly by opening the paracellular pathways.

GC-MS analysis of Polygala rosmarinifolia Wights & Arn.

This study was carried out to analyze the active constituents present in the whole plant of Polygala rosmarinifolia. Twelve compounds in ethanol extract were identified by Gas chromatography-Mass spectrometry (GC-MS) analysis. 1, 5–Anhydro-d-mannitol (73.35%) was the prevailing compound in ethanol extract, which is suggested to be an anticancer compound. This is the first report of identification of active constituents from whole plant of Polygala rosmarinifolia.

Protective effects of 3, 4-di-O-methyl-1,2,5,6-D-Mannitol tetranitrate on myocardial ischemia induced by ligating coronary artery in rats / 中国药学杂志

OBJECTIVE: To study the effects of 3, 4-di-O-methyl-1, 2, 5, 6-D-mannitol tetranitrate(DMMTN) on acute myocardial ischemia induced by ligating coronary artery in rats. METHODS: Acute myocardial ischemia model was developed by ligating the anterior descending branch of left coronary artery in rats. The rats were randomly divided into 6 groups: sham group, model group, Lunanxinkang group, low-dose (15 mg · kg-1) DMMTN group, middle-dose (30 mg · kg-1) DMMTN group and high-dose (60 mg · kg-1) DMMTN group. The changes of ST segment and T segment of electrocardiogram at different moment were recorded after myocardial ischemia injury. At 3 h after ligation, the myocardial infarct size was measured by nitroblue tetrazolium (NBT) staining method. And the activities of creatine phosphokinase (CK), lactate dehydrogenase (LDH) and superoxide dismutase (SOD), and the content of malondialdehyde (MDA) were determined to evaluate the protective effects of DMMTN. RESULTS: DMMTN could reduce the size of myocardial infarct significantly, inhibit the rising of ST segment and T segment of electrocardiogram, decrease the level of CK, LDH and MDA, and increase the activity of SOD. CONCLUSION: DMMTN showed obvious protective effects on acute myocardial ischemia induced by ligating the coronary artery in rats. Copyright 2012 by the Chinese Pharmaceutical Association.