title: Improved enzyme-mediated synthesis and supramolecular self-assembly of naturally occurring conjugates of β-sitosterol.
abstract: Naturally occurring acylated β-sitosteryl glucosides have been investigated for their novel properties. The synthetic protocol based on the literature data was improved and optimized. The main improvement consists in employing systems of ionic liquids combined with organic solvents in lipase-mediated esterification of (3β)-stigmast-5-en-3-yl β-d-glucopyranoside to get (3β)-stigmast-5-en-3-yl 6-O-acyl-β-d-glucopyranosides. Maximum yields of these products were achieved with Candida antarctica lipase B immobilized on Immobead 150, recombinant from yeast, in absolute THF and in the presence of either ionic liquid [1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM]BF4) or 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM]PF6)] employed. Pharmacological activity of (3β)-stigmast-5-en-3-yl 6-O-acyl-β-d-glucopyranosides was studied in tests on MCF7 tumor cell lines; the compounds displayed moderate activity which was higher than the activity of β-sitosterol. Supramolecular characteristics were discovered at (3β)-stigmast-5-en-3-yl 6-O-dodecanoyl-β-d-glucopyranoside that formed supramolecular polymer through multiple H-bonds in a methanol/water system (60/40). Its formation was confirmed by the independent UV-vis measurements during certain time period, by variable temperature DOSY-NMR measurement in deuteriochloroform, and visualized by transmission electron microscopy (TEM) and atomic force microscopy (AFM) showing chiral helical structures and complex superassembly systems based on fibrous supramolecular polymer. In contrary, no such properties have been observed for the other two (3β)-stigmast-5-en-3-yl 6-O-acyl-β-d-glucopyranosides under the given experimental conditions.
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Isotope Laboratory, Vídeňská 1083, 14220 Prague 4, Czech Republic; University of Chemistry and Technology, Department of Chemistry of Natural Compounds, Technická 5, Czech Republic.
authors.forename: Martina
authors.initials: M
authors.lastname: Wimmerová
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Isotope Laboratory, Vídeňská 1083, 14220 Prague 4, Czech Republic.
authors.forename: Věra
authors.initials: V
authors.lastname: Siglerová
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo náměstí 2, 16610 Prague 6, Czech Republic.
authors.forename: David
authors.initials: D
authors.lastname: Šaman
authors.affiliation: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Sq. 2, 162 06 Prague 6, Czech Republic.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Šlouf
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo náměstí 2, 16610 Prague 6, Czech Republic.
authors.forename: Eva
authors.initials: E
authors.lastname: Kaletová
authors.affiliation: Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Isotope Laboratory, Vídeňská 1083, 14220 Prague 4, Czech Republic; University of Chemistry and Technology, Department of Chemistry of Natural Compounds, Technická 5, Czech Republic. Electronic address: wimmer@biomed.cas.cz.
authors.forename: Zdeněk
authors.initials: Z
authors.lastname: Wimmer
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D006860:Hydrogen Bonding; D052578:Ionic Liquids / Q000737:chemistry; D008049:Lipase / Q000378:metabolism; D061986:MCF-7 Cells; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D012855:Sitosterols / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D052578:Ionic Liquids; D012855:Sitosterols; C025473:gamma-sitosterol; D008049:Lipase
keywords: Acylated steryl glycoside; Ionic liquid; Lipase; Pharmacological activity; Supramolecular self-assembly; β-Sitosterol