The Use of Exoglycosidases for the Assay of Two New Enzymatic Substrates, b-D-xylopyranosyl-4-nitrocatechol-1-yl and a-lactosyl-4-nitrocatechol-1-yl

Abstract

Glycosylation acceptor, 4-nitrocatechol, has been prepared via 4-nitrocatechol sulfate (2-hydroxy-5-nitrophenyl sulfate). The two carbohydrates, D-xylose and lactose, were peracetylated and then served as glycosylation donors in a modified Helferich glycosylation method, by using BF3� OBu2 as a promotor. The new synthesized glycosides were crystallized from ethanol and then submitted to Z�mplen saponification and separated by preparative thin layer chromatography (TLC). We have isolated two xylosides. Reaction mixture of lactoside proved to be unitary, a single product could be isolated. Small portions of the synthetic glycosides were re-acetylated and their 1H and 13C NMR spectra registered. The two separated xylosides were b- and a-xylopyranoside-4-nitrocatechol-1-yl. Being submitted to the action of an enzymatic extract from digestive tract of snail (Helix pomatia) only the b-anomer was susceptible to enzymatic hydrolysis. The isolated lactoside proved to be the a-isomer. Under the action of an enzymatic extract from wheat (Triticum aestivum) germs, it was sequencially cleaved, as indicated by a kinetic TLC analysis.