An Improved Helferich Method for the α/ß-Stereoselective Synthesis of 4-Methylumbelliferyl Glycosides for the Detection of Microorganisms.

An improved Helferich method is presented. It involves the glycosylation of 4-methyl-umbelliferone with glycosyl acetates in the presence of boron trifluoride etherate combined with triethylamine, pyridine, or 4-dimethylaminopyridine under mild conditions, followed by deprotection to give fluorogenic 4-methylumbelliferyl glycoside substrates. Due to the use of base, the glycosylation reaction proceeds more easily, is uncommonly α- or ß-stereoselective, and affords the corresponding products in moderate to excellent yields (51%-94%) under appropriate conditions.

[Evaluation on effects of chromogenic medium in rapid detection of Coliform and Escherichia coli].

OBJECTIVE: To evaluate the detective efficacy of Chromogenic Coliform and Escherichia Coli Agar (CCEA). METHODS: A new chromogenic medium CCEA prepared by Huankai laboratory was used to compare with a classical medium of violet red bile agar (VRBA), and other two Chromogenic media Agar I and Agar II by detecting separately 11 reference strains, thirteen sterile samples with Coliform or E.coli and other four samples, and the accordant rates of detection were observed. RESULTS: CCEA had the good selectivity. To seven kinds of quality strains in the resultant analysis, CCEA with VRBA and Agar I had not shown salience difference (P > 0.05), and CCEA with Agar II had significant difference (P < 0.05). CCEA showed more advantages than the Agar II. To thirteen sterile samples with Coliform or E.coli in resultant analysis, CCEA with Agar I and Agar II had shown no significant difference (P > 0.05), while CCEA with VRBA had significant difference (P < 0.05). CCEA might be more advantageous than the VRBA. In analysis of the four actual samples of Coliform, CCEA with VRBA, Agar I and Agar II showed no significant difference (P > 0.05). The accordant rates were 90%, 71.88%, 86.25% and 81.25% respectively, showing CCEA > Agar I > Agar II > VRBA. To two actual samples of E.coli in the resultant analysis, the CCEA with Agar I and Agar II had not shown significant difference (P > 0.05). The accordant rates were 100% respectively. CONCLUSIONS: The CCEA might be more advantageous than the VRBA, having the same efficacy as with Agar I and Agar II.

Synthesis of precipitating chromogenic/fluorogenic ß-glucosidase/ß-galactosidase substrates by a new method and their application in the visual detection of foodborne pathogenic bacteria.

We developed a new efficient method for the synthesis of important indoxyl glycoside substrates for ß-glucosidase and ß-galactosidase by using 1-acetylindol-3-ones as intermediates. This method was used to synthesise novel precipitating fluorogenic substrates for ß-glucosidase based on 2-(benzothiazol-2'-yl)-phenols. We also assessed the application of these substrates in the detection of foodborne pathogenic bacteria.