| Flavonoids are ubiquitous natural organic compounds, which are theproducts of botanic metabolizability. They display a wide range of biological activities.For instance, they have been pharmacologically shown with the effects ofantidysrhythmic, antioxidant, inhibiting cardiovascular disease and tyrosinekinases.Therefore, flavonoids have good value for development and application. However, theirbiological utilization rates are low and the doses are high for their poor solubilities,which limit their wide applications. Modifying flavonoids with chemical methods andenriching the species and properties of them are not only the important tasks in today'sresearch field but also the sources to find new promising leading compounds andbiologically active components.Firstly, the structure and classification, properties and applications of flavonoidsare summarized. The sulfonation reaction and bromination reaction are discussed bystudying references. At the same time, the flavonoids sulfo-group andthe metal ionsself-assembled mainly by the action of hydrogen bonding and aromatic stacking is alsointroduced. The sulfonate coordination complexes with DNA are investigated.Secondly, hesperetin, luteoin and baicalein, as the leading compounds, weremodified. 3',4',5,7-tetramethoxylflavanone (1), 3',5-dihydroxy-4',7-dimethoxy flavone(3), baicalein-8-sulfonate sodium (5) were synthesized and characterized by IR, ~1HNMR, element analysis and X-ray single-crystal diffraction analysis. On the other hand,using irisolidone as a starting compound, 5,6,7-trihydroxy-4'-methoxylisoflavone (7)and 8-bromo-5,7-dihydroxy-4',6-dimethoxylisoflavone (8) were synthesized bydemethylation and bromination reaction, respectively. Sulfonation reaction obtainedsodium 5,6,7-trihydroxy-4'-methoxylisoflavone-3'-sulfonate (9) and sodium 8-bromo-5,7-dihydroxyl-4',6-dimethoxylisoflavone-3'-sulfonate (10). They were allcharacterized by IR, ~1H NMR and element analysis. Then, compounds (9) and (10)were assembled with different metal ions. Eight compounds were obtained, they werehexaaquacobalt (Ⅱ) bis(4'-methoxy-5,6,7-trihydroxyisoflavone-3'-sulfonate)tetrahydrate (11), hexaaquazinc (Ⅱ) bis(4'-methoxy-5,6,7-trihydroxyisoflavone-3'-sulfonate) tetrahydrate (12), hexaaquacobalt (Ⅱ) bis(8-bromo-6,4'-dimethoxy- 5,7-dihydroxyisoflavone-3'-sulfonate) dehydrate (13), hexaaquazinc (Ⅱ)bis(8-bromo-6,4'-dimethoxy-5,7-dihydroxyisoflavone-3'-sulfonate) dehydrate (14),hexaaquairon (Ⅱ) bis(8-bromo-6,4'-dimethoxy-5,7-dihydroxyiso-flavone-3'-sulfonate)dehydrate (15), hexaaquanickel (Ⅱ) bis(8-bromo-6,4'-dimethoxy-5,7-dihydroxyisoflavone-3'-sulfonate) dehydrate (16), hexaaquamagnesium (Ⅱ) bis(8-bromo-6,4'-dimethoxy-5,7-dihydroxyisoflavone-3'-sulfonate) dehydrate (17) andhexaaquacadmium (Ⅱ) bis(8-bromo-6,4'-dimethoxy-5,7-dihydroxyisoflavone-3'-sulfonate) dehydrate (18). Crystal structures of 7, 11-18 were determined by X-raysingle-diffraction analysis. In compound 1, 3 and 7, O—H...O hydrogen bonding,C—H...O soft hydrogen bonding, C—H...πinteraction andπ...πstacking heldtogether with them to form a three-dimensional super-molecular structure. In otherflavonoids sulfonates, O—H...O hydrogen bonding and C—H...O soft hydrogenbonding existed among sulfo-group, latticed water molecules, coordinated watermolecules, methoxyl groups and hydroxyl groups, which formed a hydrophilic region.C—H...O soft hydrogen bonding, C—H...πinteraction andπ...πstacking existedbetween the flavonoids skeletons, which formed a hydrophobic region. The sulfo-groupwas a vital bridge between the hydrophilic region and the hydrophobic region. Thehydrogen bonds,π-πstacking interactions and the electrostatic interaction betweenthe caitons and the anions lead the flavonoids into three-dimensional supramolecularstructures. In the crystal structures of 13-18, O—H...Br hydrogen bonding and Br...πwere found along with hydrogen bonds and aromaticπ...πstacking interactions. Thehydrogen bonds and aromatic stacking interaction played very important role in theformation, stability and crystallization of the compound.Finally, the interaction of sodium irisolidone-3'-sulfonate and aquariumirisolidone-3'-sulfonate with calf thymus DNA in Tris-NaCl buffer solution (pH=7.1)were investigated by using fluorescence spectra. The results suggested that thecomplexes bind to DNA in intercalating mode.By modifying the flavonoids and studies on the crystal structures of sulfonatedflavonoids not only enrich the properties and species of flavonoid, but also supply thetheoretical foundations for further developing the new drug.
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