title: In silico discovery of acylated flavonol monorhamnosides from Eriobotrya japonica as natural, small-molecular weight inhibitors of XIAP BIR3.
abstract: Targeting the baculoviral inhibitor of apoptosis proteins repeat (BIR) 3 of X-linked inhibitor of apoptosis proteins (XIAP) represents an innovative strategy for the design of chemosensitizers. Acylated flavonol monorhamnosides (AFMR) from Eriobotrya japonica Lindl. (Rosaceae) were virtually predicted as ligands of the XIAP BIR3 domain by using a previously generated pharmacophore model. From the methanol leaf extract of E. japonica an enriched mixture of AFMR was obtained showing chemosensitizing potential in combination with etoposide in XIAP-overexpressing Jurkat cells. The HPLC-SPE-NMR hyphenated technique facilitated the structure elucidation of three known and two new natural AFMR. The main constituent and virtual hit, kaempferol-3-O-α-l-(2″,4″-di-E-p-coumaroyl)-rhamnoside (3) was isolated from the enriched fraction. Applying a fluorescence polarization based binding assay, 3 was identified as XIAP BIR3 ligand with a dose-dependent affinity (IC₅₀ 10.4 μM). Further, 3 induced apoptosis in XIAP-overexpressing Jurkat cells and activated caspase-9 in combination with etoposide. Docking experiments revealed a major impact of the coumaric acid and sugar moieties of 3 on XIAP BIR3 binding, which was experimentally confirmed. To conclude, this study elucidates 3 as natural, small-molecular weight XIAP BIR3 inhibitor using a combination of in silico and HPLC-SPE-NMR hyphenated techniques.
authors.affiliation: Institute of Pharmacy/Pharmacognosy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Austria.
authors.forename: Petra H
authors.initials: PH
authors.lastname: Pfisterer
authors.forename: Chenxi
authors.initials: C
authors.lastname: Shen
authors.forename: Zaneta
authors.initials: Z
authors.lastname: Nikolovska-Coleska
authors.forename: Lilianna
authors.initials: L
authors.lastname: Schyschka
authors.forename: Daniela
authors.initials: D
authors.lastname: Schuster
authors.forename: Anita
authors.initials: A
authors.lastname: Rudy
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wolber
authors.forename: Angelika M
authors.initials: AM
authors.lastname: Vollmar
authors.forename: Judith M
authors.initials: JM
authors.lastname: Rollinger
authors.forename: Hermann
authors.initials: H
authors.lastname: Stuppner
mesh_terms: D001665:Binding Sites; D045744:Cell Line, Tumor; D003198:Computer Simulation; D004353:Drug Evaluation, Preclinical; D031983:Eriobotrya / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D018515:Plant Leaves / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D005419:Flavonoids; D051636:X-Linked Inhibitor of Apoptosis Protein