The first chrysin-based receptor for anions recognition: Experimental investigations, DFT studies and its in vitro antitumor activity

Anion recognition has been the focus of extensive research due to the significant role these species play in numerous physiology and environment processes. Despite the increasing interest, the construction of novel receptors rationally-designed for anions has been particularly challenging. Inspired by the unique and beautiful structures of phytochemicals, herein we designed and synthesized a novel chrysin-linked difluoroboron (Ch-FB) receptor, which is the first example of natural chrysin-based receptor for anions recognition. The recognition behavior of the Ch-FB towards various anions was investigated by UV-vis absorption and fluorescence spectroscopy. Highly sensitive and selective recognition of F-, H2PO4- and AcO- with the same 1:1 binding stoichiometry was obtained. Furthermore, Ch-FB displayed a low detection limit (1.12 mu M for F- , 1.92 mu M for H2PO4and 0.48 mu M for AcO-) and rapid response time (about 30-150 s). The binding constant (K) of Ch-FB for F- (K = (7.27 +/- 0.33) x 105 M-1) was slightly higher than that of Ch-FB for AcO- (K = (1.21 +/- 0.03) x 105 M-1) and H2PO4- (K = (1.02 +/- 0.05) x 105 M-1). This anions-sensing mechanism could be attributed to the strong hydrogen bonding between the hydroxyl group of Ch-FB and the three anions, which was also confirmed by the 1H NMR experiments and density functional theory (DFT) calculations. Importantly, the antitumor activity of receptor Ch-FB against two cancer cell lines (MCF-7 cells and SKOV3 cells) exhibited enhanced activity in comparison with the precursor chrysin, implying its potential feasibility in further investigation of the other pharmacological activities with more novel performance.