Synthesis, light-controlled antibacterial and anti-tumor activities of Ginkgo biloba leaves polyprenols-based polypyridine metal complexes.

ABSTRACT

In this study, Ginkgo biloba leave polyprenols (GBP) and polypyridine metal complex were individually utilized as functional ligand and main ligand, four kinds of novel GBP-based polypyridine metal complexes were successfully synthesized and their cell absorption capacity, light-dark stability, photodissociation efficiency, ROS production capacity, light-controlled antibacterial and anti-tumor activities as well as mechanisms were systematically investigated by ultraviolet visible spectrophotometer (UV-vis), confocal laser scanning microscope (CLSM), gel electrophoresis (GE), scanning electron microscope (SEM), oxford cup method, MTT method etc. The lipid water distribution coefficients of complex 1, 2 and 4 were all within the range of 0∼3, demonstrating their better cell absorption capacity and more competitive bioavailability potentiality compared with GBP. All of the synthesized complexes possessed excellent stability in a dark environment, and could conduct ligand dissociation under the condition of visible light irradiation except complex 1. In which, complex 2 and complex 4 were able to achieve degradation rates of 37.9 % and 54.4 % within 5 min, separately. In addition, complex 2 and complex 4 exhibited superior inhibitory activities on the HN-3 tumor cells on account of their stronger ROS production capacity. Moreover, the constricted expression of BCL-2 and NF-kB p-p65, especially the promoted expression of BAX may be one of the root cause. The four synthesized complexes had preferable inhibition effects against S. aureus under the condition of visible light irradiation in contrast to darkness, in which complex 4 was the best and its MIC and MBC values were 6.25 and 12.5 µg/mL, respectively. The antibacterial mechanism of the complex 4 may be in relation to the synergistic effect of multiple factors, including leakage of bacterial inclusion, change of cell membrane permeability and disruption of cell wall etc. All of the above generalized researches will pave a way for the high-value development and application of GBP-based functional products.