calycosin-7-o-beta-d-glucopyranoside and daidzein

Nonsteroidal anti-inflammatory drugs reportedly reduce the risk of developing cancer. One mechanism by which they reduce carcinogenesis involves the inhibition of the activity of cyclooxygenase-2, an enzyme that is overexpressed in various cancer tissues. Its overexpression increases cell proliferation and inhibits apoptosis. However, selected cyclooxygenase-2 inhibitors can also act through cyclooxygenase-independent mechanisms. In this study, using ultrafiltration, enzyme-immobilized magnetic beads, high-performance liquid chromatography, and electrospray-ionization mass spectrometry, several isoflavonoids in Trifolium pratense L. extracts were screened and identified. Semi-preparative high-performance liquid chromatography and high-speed counter-current chromatography were then applied to separate the active constituents. Using these methods, seven major compounds were identified in Trifolium pratense L. As cyclooxygenase-2 inhibitors: rothindin, ononin, daidzein, trifoside, pseudobaptigenin, formononetin, and biochanin A, which were then isolated with >92% purity. This is the first report of the presence of potent cyclooxygenase-2 inhibitors in Trifolium pratense L. extracts. The results of this study demonstrate that the systematic isolation of bioactive components from Trifolium pratense L., by using ultrafiltration, enzyme-immobilized magnetic beads, semi-preparative high-performance liquid chromatography, and high-speed counter-current chromatography, represents a feasible and efficient technique that could be extended for the identification and isolation of other enzyme inhibitors.

Topics: Chromatography, High Pressure Liquid; Countercurrent Distribution; Cyclooxygenase 2 Inhibitors; Enzymes, Immobilized; Genistein; Glucosides; Isoflavones; Magnetic Phenomena; Trifolium; Ultrafiltration

A novel isoflavone 7- O -glucosyltransferase PlUGT1 was isolated from Pueraria lobata . PlUGT1 could convert daidzein to daidzin, genistein to genistin as well as formononetin to ononin. Pueraria lobata roots are traditionally consumed as a rich source of isoflavone glycosides that have various human health benefits. However, to date, the genes encoding isoflavone UDP-glycosyltransferases (UGTs) have only been isolated from the roots of soybean seedlings (GmIF7GT), soybean seeds (UGT73F2) and Glycyrrhiza echinata cell suspension cultures (GeIF7GT). To investigate the isoflavone metabolism in P. lobata, 40 types of partial UGT cDNAs were isolated from P. lobata, and seven full-length UGT candidates with preferential expression in roots were identified. Functional assays in yeast (Saccharomyces cerevisiae) revealed that one of these UGT candidates, designated PlUGT1 (official UGT designation UGT88E12), efficiently glycosylated isoflavone aglycones at the 7-hydroxy group. Recombinant PlUGT1 purified from Escherichia coli cells was characterized and shown to be relatively specific for isoflavone aglycones, while flavonoid substrates were poorly accepted. The biochemical results suggested that PlUGT1 was an isoflavone 7-O-glucosyltransferase. The deduced amino acid sequence of PlUGT1 shared only 26 % identity with GeIF7GT, 27 % with UGT73F2 and 63 % with GmIF7GT. The PlUGT1 gene was highly expressed in P. lobata roots relative to other organs and strongly induced by methyl jasmonate signal in P. lobata cell suspension culture. The transcript abundance of PlUGT1 was correlated with the accumulation pattern of isoflavone glycosides such as daidzin in P. lobata plants or in cell suspension culture. The biochemical properties and gene expression profile supported the idea that PlUGT1 could play a role in isoflavone glycosylation in P. lobata.

Topics: Acetates; Cloning, Molecular; Cyclopentanes; Glucosides; Glucosyltransferases; Isoflavones; Molecular Sequence Data; Oxylipins; Phylogeny; Plant Proteins; Plant Roots; Pueraria