Paramagnetic NMR shift, spectroscopic and molecular modeling studies of lanthanide(III)-morin complexes

Synthesis and Structural Investigation of New Bio-Relevant Complexes of Lanthanides with 5-Hydroxyflavone: DNA Binding and Protein Interaction Studies

In the present work, we attempted to develop new metal coordination complexes of the natural flavonoid 5-hydroxyflavone with Sm(III), Eu(III), Gd(III), Tb(III). The resultant hydroxo complexes have been characterized by a variety of spectroscopic techniques, including fluorescence, FT-IR, UV-Vis, EPR and mass spectral studies. The general chemical formula of the complexes is [Ln(C₁₅H₉O₃)₃(OH)₂(H₂O)_x]·nH₂O, where Ln is the lanthanide cation and x = 0 for Sm(III), x = 1 for Eu(III), Gd(III), Tb(III) and n = 0 for Sm(III), Gd(III), Tb(III), n = 1 for Eu(III), respectively. The proposed structures of the complexes were optimized by DFT calculations. Theoretical calculations and experimental determinations sustain the proposed structures of the hydroxo complexes, with two molecules of 5-hydroxyflavone acting as monoanionic bidentate chelate ligands. The interaction of the complexes with calf thymus DNA has been explored by fluorescence titration and UV-Vis absorption binding studies, and revealed that the synthesized complexes interact with DNA with binding constants (K_b) ~ 10⁴. Human serum albumin (HSA) and transferrin (Tf) binding studies have also been performed by fluorescence titration techniques (fluorescence quenching studies, synchronous fluorescence spectra). The apparent association constants (K_a) and thermodynamic parameters have been calculated from the fluorescence quenching experiment at 299 K, 308 K, and 318 K. The quenching curves indicate that the complexes bind to HSA with smaller affinity than the ligand, but to Tf with higher binding affinities than the ligand.

Properties and applications of flavonoid metal complexes

Flavonoid metal complexes have a wide spectrum of activities as well as potential and actual applications.

Synthesis and characterisation of morin reduced gold nanoparticles and its cytotoxicity in MCF-7 cells

There is significant interest in investigating the therapeutic potential of phytochemical reduced and bound gold nanoparticles (AuNPs) as it bridges the gap between nanotechnology and therapy. In the present study, AuNPs prepared using the flavonoid morin (mAuNPs) are characterised and have been studied for their anti-cancer effects. The -OH groups of morin reduce Au(3+) and stabilize Au(0) to form spherical and crystalline mAuNPs. These mAuNPs are biocompatible towards normal human blood cells and breast epithelial cells. Through TEM analysis, we report that they are readily taken up by breast cancer cells (MCF-7) to induce cell death. Apoptosis has also been assessed by other morphological observations and cell viability studies. Flow cytometric studies reveal that the cells undergo a transient phase of apoptosis progressing towards secondary necrosis as the dose and time of mAuNPs treatment increases. The ability of mAuNPs to induce cell death in MCF-7 cells indicates its potential as an anti-cancer agent.