ABSTRACT
Multivalent carbohydrate ligands have been prepared by assembling alpha-cyclodextrin-based pseudo-rotaxanes through "click chemistry". The inclusion complex formed by a lactosyl-alpha-CD conjugate and a decane axle carrying a lactosyl stopper at one extremity and an azido group at the other end was dimerized by bis-propargyl spacers of different lengths to provide oligorotaxanes having adjustable threading ratios. For the first time, saccharidic ligands have been introduced on rotaxanes both as a biological recognition element and as a capping group. The supramolecular species have been isolated and characterized by mass spectrometry as well as by 1D and DOSY NMR experiments. Their ability to inhibit the binding of Arachis hypogaea agglutinin to asialofetuin, assayed by enzyme linked lectin assays (ELLA), was shown to be valency-dependent.
Subject(s)
Asialoglycoproteins/metabolism , Peanut Agglutinin/metabolism , Rotaxanes/chemical synthesis , Rotaxanes/metabolism , alpha-Cyclodextrins/chemical synthesis , alpha-Cyclodextrins/metabolism , alpha-Fetoproteins/metabolism , Arachis/chemistry , Arachis/metabolism , Fetuins , Ligands , Magnetic Resonance Spectroscopy , Protein Binding , Rotaxanes/chemistry , alpha-Cyclodextrins/chemistryABSTRACT
Hederagenin saponins are largely represented in nature and possess many biological activities such as haemolytic, antiviral, fungicidal, molluscicidal or cytotoxic, partially due to their interaction with the cell membrane. The lysis of erythrocytes (haemolysis) is a simple test to evaluate this adsorption, and this activity has been linked to the structure of the aglycone and also depends on the sugar moiety of the saponin. To further complete our study of the structure-activity relationships of triterpenoid saponins, alpha-hederin and related hederagenin diglycosides were synthesized to better understand the influence of the second sugar (alpha-L-rhamnose, beta-D-xylose or beta-D-glucose) and the substitution of this sugar on alpha-L-arabinose (position 2, 3 or 4). Haemolysis and cytotoxic activity on KB cells were tested. These compounds probably interact with membrane cholesterol and produce destabilization of the membrane inducing haemolysis. Cytotoxicity could involve the same mechanism, although some saponins induce an apoptotic process. The nuclear structure of the KB cell was thus investigated by confocal microscopy. The cytotoxic activity of a second group of hederagenin glucoside saponins was also evaluated. Our results showed that cytotoxicity was a result of both the sugar part and the structure of genin (carboxylic acid or methyl ester).
Subject(s)
Apoptosis/drug effects , Hemolysis/drug effects , Oleanolic Acid/analogs & derivatives , Arabinose/chemistry , Cell Line, Tumor , Cell Nucleus/drug effects , Glucose/chemistry , Glycosylation , Humans , Molecular Structure , Oleanolic Acid/chemistry , Oleanolic Acid/toxicity , Saponins/chemistry , Saponins/toxicity , Structure-Activity RelationshipABSTRACT
Glycosylation of hederagenin with the trichloroacetimidate derivatives of six commercial disaccharides (D-cellobiose, D-lactose, D-maltose, D-melibiose, D-gentiobiose, D-isomaltose) was performed giving the protected saponins in high yields. Deprotection then gave the saponins which were transformed into the corresponding methyl esters. The hemolytic activity of these synthetic hederagenin diglycosides was measured in order to establish structure-activity relationships based on the type and sequence of the attached sugar for the free carboxylic acid and methyl ester saponins.
