Characterization and Stability of the AntimonyQuercetin Complex

Purpose: Quercetin is a flavonoid known for its therapeutic properties and for forming complexes. Although the antimonyquercetin (SbQ) complex has been produced before, no previous exploration of its characteristics has been published in literature. Thus, this study aimed to characterize this complex, assess its stability and investigate its complexation site through its antibacterial activity. Methods: The SbQ complex was synthetized using Sb(III) potassium tartrate trihydrate and quercetin anhydrous (1:1) (v/v) as a solution and dried using three methods: rotaevaporation, lyophilization and spray drying. The material, in solution, was analyzed by UVvis and fluorimetry; and, in the powder, by Xray diffraction (XRD), both scanning electronic and fluorescence microscopy and infrared spectroscopy (FTIR). Antimicrobial activity was evaluated via broth microdilution. Results: UVvis exhibited a shoulder peak at 291 nm indicating metal chelation at Cring of quercetin and confirmed 1:1 stoichiometry. Spectrofluorimetry showed an increase of intensity with the complex formation with an emission band (525 nm). After drying, XRD and SEM indicated loss of crystallinity and a difference in shape and size of the complex compared to its precursors. FTIR suggested by a shift of frequency of the carbonyl group (1661 cm1) that the quercetin bond to antimony by the C3, followed by positions C5 and C4 carbonyl, which has been confirmed by MIC through the structureactivity relationship of the antibacterial activity of quercetin. Conclusion: These results provided a characterization of SbQ complex with the confirmation of its binding site, working as a guide for future studies involving this complex.