Metal - based curcumin and quercetin complexes: cell viability, ROS production and antioxidant activity

Flavonoids, also known as polyphenols, contain carbonyl and hydroxyl groups and are capable of forming complexes with metal ions. In this perspective, complexation of curcumin and quercetin were achieved by using magnesium and calcium divalent cations to enhance the solubilities of curcumin and quercetin. The cell proliferation and antioxidant effects were tested on colon carcinoma cells (HCT-116). Metal complexes of curcumin and quercetin were characterized using XRD analysis, TOF mass spectrometry, FT-IR and UV-Vis spectroscopies. A solubility assay was conducted to demonstrate the improvements in the solubility of curcumin and quercetin. Cell viability was measured by cell viability detection kit-8 (CVDK-8) and imaged by crystal violet assay. 2′,7′-dichlorodihydrofluorescein diacetate fluorogenic (DCFH-DA) dye was used to determine intracellular reactive oxygen species (ROS) production. Radical scavenging activity of metal complexes were analyzed by 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH) assay. Cell viability, reactive oxygen species (ROS) production assays reveal that curcumin and its complexes showed better antiproliferative effect at lower concentrations compared to quercetin complexes. In contrast, quercetin complexes had better radical scavenging activity compared to curcumin complexes based upon DPPH assay. Metal complexes of curcumin and quercetin can be useful to elucidate alternative strategies in cancer prevention and therapy by enhancing their solubilities.