Interactions of Flavonoids with Biomacromolecules

Flavonoids are widely distributed in the plant kingdom and have broad-spectrum pharmacological activities and extensive biological effects. The pharmacological investigations indicated that flavonoids can regulate the structure and functions of proteins and nucleic acids by controlling their signaling pathways and expressions to achieve their effects. In this review, the main approaches for investigating the interaction of flavonoids with biomacromolecules in vitro and related theoretical issues were presented and some important parameters including their binding constants, the number of binding site, and the position of the flavonoids on the protein have been summarized. The investigation details of the interaction mechanisms and binding mode were compared and discussed. The binding sites of flavonoids on the protein were usually determined by replacement experiments using warfarin (WAR) (site I) and ibuprofen or diazepam (site II) as site markers, and the structural alterations of the protein or flavonoids before and after the combinations were probed by Fourier transform infrared (FTIR), circular dichroism (CD) or UV absorption methods. Flavonols attracted much attention due to their special structural features and spectroscopic characteristics. The interaction of nucleic acids with flavonols has been the focus of extensive research in recent years. Investigation of the interaction between flavonoids and biomacromolecules can provide useful knowledge for optimizing molecular structure of the drugs, prescriptions and route of administration, and also the information for their bioavailability and bioactivity. Keywords: Binding mode, flavonoids, flavonol, fluorescence enhancement, nucleic acids, protein, spectroscopic methods, Fourier transform infrared (FTIR), circular dichroism (CD), warfarin (WAR), phytotherapeutics, genistein, quercetin, methoxylated !avones, proanthocyanidins