Indium(III) Triflate–Mediated One-Step Preparation of Glycosyl Halides from Free Sugars

In(OTf)₃ has been found to be an efficient catalyst for the direct conversion of reducing sugars to their respective acylated glycosyl halides in good yields under mild conditions. The glycosyl halides so obtained can be converted to alkyl glycosides in the same pot by reacting them with the respective alcohols in good yield.     

Separation and purification of ergosterol and stigmasterol in Anoectochilus roxburghii (wall) Lindl by high-speed counter-current chromatography

Ergosterol and stigmasterol are the most common phytosterols in the traditional Chinese medicine. They are two major sterol compounds in Anoectochilus roxburghii (wall) Lindl (A. roxburghii) and have been proved to have many important biological activities. A method by using high-speed counter-current chromatography (HSCCC) has been successfully developed for separation and purification of ergosterol and stigmasterol in A. roxburghii simultaneously in this paper. The optimum conditions used in this method were as follows: The two-phase solvent system consisted of n-hexane-ethylacetate-butanol-methanol-water (3.5:0.3:0.5:2.5:0.3, v/v); the rotation speed was 900 rpm; the flow rate of the lower phase was 1.5 mL/min. About 36.5 mg of ergosterol and 43.6 mg of stigmasterol were obtained from 100 g of A. roxburghii. The purity of ergosterol and stigmasterol was examined to be 92.0 and 95.5%, respectively, by using HPLC. The chemical structures of these components were identified by UV spectra, FT-IR, MS, (1) H-NMR and (13) C-NMR. The results demonstrated that high-speed counter-current chromatography was a feasible method to separate and purify ergosterol and stigmasterol from the herb. This separation and purification method was more effective than many other conventional techniques.     

In situ demonstration and quantitative analysis of the intrinsic properties of glycoside hydrolases

Based on digital image analysis techniques and a series of optimizations in native electrophoresis, a new direct method to simultaneously detect the intrinsic properties of each active component in the enzymatic system of glycoside hydrolase was established. The key technique is that the concentration changes of substrate (or product) on the gel can be determined quantitatively by the gray value changes of the corresponding band after electrophoretic separation. In this manner, the catalytic characteristics of each glycoside hydrolase component were demonstrated in situ and were easily determined after immersing the gel in a series of solutions containing substrates or their derivatives. Because of its high throughput, great sensitivity, and convenient operation, this method can be used to demonstrate the natural diversity of glycoside hydrolases and to study spatial and temporal regulation in multienzyme expression systems. Thus, it is an effective approach to study the functional proteomics of glycoside hydrolases.