Transition Metal Coordination Complexes of Flavonoids: A Class of Better Pharmacological Active Molecules to Develop New Drugs

Flavonoid metal ion complexes are one of the classes of biologically active molecules with immense pharmacological potential, including antioxidant, antidiabetic, antimicrobial, and anticancer activity, to name a few. The effectiveness of this complexion depends on the state and nature of the transition metal ions and on the position to which the metal ion coordinates with their corresponding parent flavonoid. The metal coordination of flavonoids also improves the biological activities to a maximum extent compared to the parent compound. This may be attributed to many factors such as metal ions, coordination sites, structural configuration, and stability of the complexes. On the other hand, some of the metal ion complexes reduce the biological efficiency of the corresponding parent flavonoids, which can be due to the shift from antioxidant to pro-oxidant nature as well as the stability of the complexes both in in vitro and in vivo conditions. However, the literature on the stability of flavonoid metal ion complexes in in vivo conditions is very scanty. Therefore, this review summarizes and critically addresses all these parameters a favor together in a single slot that favours for the researchers to put forward to understand the mode and detailed molecular mechanism of flavonoid metals complexes compared with their corresponding parent flavonoids.