Purification of an isoflavonoid 7-O-β-apiosyl-glucoside β-glycosidase and its substrates from Dalbergia nigrescens Kurz

A beta-glycosidase was purified from the seeds of Dalbergia nigescens Kurz based on its ability to hydrolyse p-nitrophenyl beta-glucoside and beta-fucoside. This enzyme did not hydrolyze various glycosidic substrates efficiently, so it was used to identify its own natural substrates. Two substrates were identified, isolated and their structures determined as: compound 1, dalpatein 7-0-p-D-apiofuranosyl-(l -> 6)-beta-(D)-glucopyranoside and compound 2, 6,2 ',4 ', 5 '-tetramethoxy-7-hydroxy-7-O-beta-(D)-apiofuranosyl-(1 -> 6)-beta-(D)-glucopyranoside (dalnigrein7-O-beta-(D)-iofuranosyl-(1 -> 6)-beta-(D)-glucopyranoside). The beta-glycosidase removes the sugar from these glycosides as a disaccharide, despite its initial identification as a beta-glucosidase and beta-fucosidase. (c) 2005 Elsevier Ltd. All rights reserved.