Synthesis of Ester-Linked Paclitaxel-Glycoside Conjugate as a Water-Soluble Paclitaxel Derivative—Maltoside Modification of Paclitaxel through Ester-Linker (Ester-Spacer)

To synthesize a water-soluble paclitaxel derivative, the anomers of diols of allyl 2,3,4-tri- O-benzyl-6- O-tritylglycoside (maltoside) were prepared, which can be separated by chromatographic procedure. One anomer was converted into α-glycosyloxyacetic acid (maltosyloxyacetic acid) by oxidative cleavage of the diol and subsequent oxidation. Ester-linked paclitaxel-glycoside conjugate, 7-glycolylpaclitaxel 2″- O-α-maltoside, was provided by condensation of 2′-TES paclitaxel with α-glycosyloxyacetic acid (maltosyloxyacetic acid) followed by deprotection of hydroxy groups.

Isolation and characterization of a novel glucosyltransferase involved in production of emodin-6-O-glucoside and rhaponticin in Rheum palmatum

Anthraquinones are widely distributed in various organisms and known as bioactive ingredients. Some of the anthraquinones accumulate as glycosides in higher plants. Plant secondary product glycosyltransferases (PSPGs) are the well-characterized enzymes producing plant secondary metabolite glycosides. However, PSPGs involved in the formation of anthraquinone glycosides remains unclear. The rhizome of Rheum palmatum contains anthraquinones as laxative agents, some of which are accumulated as glucosides. We isolated a glucosyltransferase, R. palmatum UDP-glycosyltransferase (RpUGT) 1 from the rhizome of R. palmatum, and characterized functionally. RpUGT1 glucosylated emodin yielding emodin-6-O-glucoside, and it also glucosylated rhapontigenin, a compound belonging to stilbenes, yielding rhaponticin. The expression patterns of RpUGT1 and the accumulation of the metabolites revealed that RpUGT1 contributes to the production of these glucosides in R. palmatum. These results may provide important information for the substrate recognition of the PSPGs for anthraquinones and stilbenes.

Glycosylation of Artepillin C with Cultured Plant Cells of Phytolacca americana

Biotransformation of artepillin C was investigated using cultured plant cells as biocatalysts. Artepillin C was converted into its 4- and 9-β-D-glucosides, and 4,9-β-D-diglucoside by cultured cells of Phytolacca americana. In contrast, cultured Ipomoea batatas cells glucosylated artepillin C to only its 4- and 9-β-D-glucosides.