Discovery of Chemosensitizing Flavonoids from Eriobotrya japonica Using in silico and HPLC-SPE-NMR Techniques

Mimetics of the second mitochondria-derived activator of caspases (Smac) increase the sensitivity of tumor cells towards chemotherapeutics in cancer therapy [1]. Our aim was the discovery of naturally derived small molecule Smac-mimetics from the medicinal plant Eriobotrya japonica Lindl. (Rosaceae), which is known to contain cytotoxic constituents [2]. Using a previously generated and validated pharmacophore model [3] 122 3D-molecules (ERIO-database) of known constituents from the leaves of E. japonica were subjected to virtual screening. We focused on acylated flavonol monorhamnosides (AFMR) as promising phytochemical class due to the statistical evaluation of the virtual hits. AFMR were identified in the methanol extract by LC-MS and enriched by different chromatographic methods. In the Nicoletti test [4], the combination of the AFMR-mixture with sub-optimal concentrations of the chemotherapeutic etoposide strongly induced cell death in S-Jurkat and XIAP overexpressing Jurkat cells. Since the AFMR-mixture was not separable by conventional methods, we used an HPLC-SPE-NMR approach for the structural identification of single compounds. The combination of the in silico and HPLC-SPE-NMR techniques enabled the insight into ligand-target interactions of single compounds from a complex mixture.