Streptozotocin

Effects of the intragastric administration of various samples on the body weight of mice are shown in Fig. 3, which was produced using Origin software. It could be observed that the variation in the trend of the average weights of all treated groups, no matter the sample doses, was similar to that of the streptozocin (STZ)-model group. From 1 to 4 weeks there was little difference in the average weight of the mice between the seven groups.Within the first four weeks, after streptozocin (STZ) injection, all sample groups showed no evident difference in the average weights. However, the gain ratio of the body weight of treated mice slowed within the 4th week after streptozocin (STZ) injection, which may be due to a metabolic disorder caused by injection of streptozocin (STZ).Within the 4th week after the streptozocin (STZ) injections it could also be found, by careful observation, that the positive rate of weight gain of the streptozocin (STZ)-model group seemed constant, and was obviously higher than that of all other treated groups. This may be because the streptozocin (STZ)-model mice had not been fed the antioxidant substances, so the metabolism of these streptozocin (STZ)-model mice was not disordered, resulting in an large increase in body weight. In other words, the mice treated with the sericin/ethanol extracts for 4 weeks had strong anti-oxidation activities and protection against streptozocin (STZ) oxidation. It is possible that the administration of the sericin/ethanol extracts could inhibit the effect of obesity resulting from streptozocin (STZ) injections.

Streptozocin (STZ)-induced diabetic mice Mice were weighed every week. The mice were fasted for 12 h before administration of Streptozocin (STZ) (100 mg kg^-1), buffered in cold sodium citrate (pH 4.2–4.5), by intraperitoneal injection. An Accu-check meter was employed to measure fasting blood glucose levels. Blood samples were collected from the tail vein. Fasting blood glucose was measured before induction in order to ensure that all experimental animals had normal FBG levels. During the induction period, the FBG levels were measured on the third day after the Streptozocin (STZ) injection. Mice with high levels of blood glucose were randomly assigned to different treatment groups. For labeling, the picric acid test was used to number the mice in each group. After the four-week treatment, the FBG levels of all mice were measured to determine whether the treatment had a glucose-lowering effect in diabetic mice.

For instance, a derivative of N-nitrosoaniline, dephostatin (Fig. 1, A) is known to be a potential inhibitor of cysteine-containing enzymes such as protein tyrosine phosphatases, papain and caspase. The cyclic-nitrosamines B and C have been found to inhibit thrombus formation in the arterioles and venules of rats. Although N-methyl-N-nitrosourea is a cancer inducer, its derivatives were found to be potent anti-tumor agents. For example, carmustine (Fig. 1, D) and related compounds (e.g. lomustine and semustine) are widely used as alkylating agents in chemotherapy. Streptozocin (E) is a sugar derived N-methylnitrosourea used as an antibiotic and anti-neoplastic agent. In addition, streptozocin is also a well- known diabetogenic agent currently used in medical research to produce animal models for hyperglycemia and Type 1 diabetes. The N-nitrosohydroxylamine derivative dopastin (Fig. 1, F) is used as an experimental antihypertensive agent that inhibits copper-dependent dopamine β-hydroxylase efficiently. Similarly, N-nitroso-N-cyclohexylhydroxylamine (G) is used as a synergistic agent which increases the insecticidal activity of chlordane.

During the course of our studies directed towards synthesis of glycosamine containing glycoconjugates, we serendipitously came across the formation of a 1,2-cis-fused bicyclic furanoside oxazolidinone from D-glucosamine, which is quite difficult to prepare otherwise. There are sporadic reports on the formation of such furanoside oxazolidinone derivatives formed mostly as side products, decomposition products or as components of mixtures. In 1979, Argoudelis and co-workers, in the course of the structure determination of the antibiotic streptozocin via degradation studies, reported that the reaction of streptozocin with 2 N NaOH gave a bicyclic furanoside oxazolidinone. Hammer and co-workers reported that chlorozotocin decomposes in aqueous buffer solutions (pH 7.4) at 37 ℃ to give a complex mixture of six intramolecular five-membered ring carbamate (1,3-oxazolidin-2-one) sugars.