Synthesis, characterization, antioxidant activity and DNA binding affinity of novel metal complexes based on amentoflavone extracted from Ginkgo biloba leaves

Abstract

Amentoflavone (Ame) is a kind of precious biflavonoid with various bioactivities. To further develop and use Ame, Ame was extracted and purified from Ginkgo biloba leaves, and Ame complexes with metal ions (Mn²⁺/Fe³⁺/Co²⁺/Ni²⁺/Cu²⁺/Zn²⁺) were synthesized for the first time. The structures of Ame complexes were characterized using UV/vis, FT-IR, HRMS and DFT calculations. Their antioxidant activity was evaluated using pyrogallol auto-oxidation and ABTS methods. DNA binding affinity was explored via fluorescence studies and molecular docking simulations. The structural analysis indicated that the stoichiometric ratios of Ame and Mn²⁺/Co²⁺/Ni²⁺/Cu²⁺/Zn²⁺ were 1 : 1, and the chelation sites were between the 5″-hydroxyl and 4″-carbonyl, while the stoichiometric ratio of Ame and Fe³⁺ was 2 : 2, and the chelation sites were between the 5″-hydroxyl and 4″-carbonyl and the 5-hydroxyl and 4-carbonyl. The investigation of pyrogallol auto-oxidation and ABTS methods demonstrated that Ame complexes had superior scavenging activities for O₂⁻˙ and ABTS⁺˙ free radicals. What's more, free radical scavenging activity of some Ame complexes was stronger or similar compared with VC. The results of fluorescence studies indicated that Ame complexes had a stronger DNA binding affinity with intercalation mode. A molecular docking study confirmed that Ame and its complexes interacted with DNA via van der Waals forces, conventional hydrogen bonding and π–π stacking effects. These results demonstrated that bioactivities of Ame could be enhanced via forming complexes with metal ions and provided theoretical support for the application of biflavonoids as potential drugs, dietary supplements and cosmetic agents.