Studies On The Structure Modification And Crystal Structures Of Isoflavone Components From Flowers Pueraria

Flowers Pueraria is the dried bud of Pueraia lobata or Pueraria thomsonii. It is a traditional Chinese herbal medicine, and can be used in therapy to counteract problems associated with alcohol drinking. Insolidone (5,7-dihydroxy-6,4'-dimethoxy- isoflavone), a kind of isoflavone, as one of the effective components in the flowers Pueraia, has the most potent inhibitory activities against ethanol, hepatic injuries and resistance to hypoxia. However, its biological utilization rate is low for its poor solubility, which limits its wide applications. Modifying isoflavones with chemical methods and enriching the species and properties of them are not only the important tasks in today's research field but also the sources to find new promising leading compounds and biologically active components.Firstly, irisolidone was isolated from flowers Pueraria. Flowers Pueraia were refluxed for 60 min with 70% ethanol three times and extracted using n-butanol, the n-butanol portion was dried on a rotary evaporator under reduced pressure to obtain a deposition. When recrystallized using 50% ethanol for 3 times, the deposition was hydrolyzed by 5% HC1 for 60 min and recrystallized 3 times from 95% ethanol to obtain irisolidone. Its purity exceeds 98% (HPLC) and yield is up to 0.8%. The method is simple and convenient, yield is high.Secondly, irisolidone as the leading compound, 5-hydroxyl-6,7,4'-trimethoxy-isoflavone, 5,6,7,4'-tetramethoxylisoflavone, 5-hydroxyl-6,4'-dimethoxy-7-ethoxy-isoflavone were synthesized. Sulfonation reaction obtained sodium 5-hydroxy-6,7,4'-trimethoxyisoflavone-3'-sulfonate, sodium 5,6,7,4'-tetrametroxyisoflavone-3'-sulfonate and sodium 5-hydroxyl-6,4'-dimetroxy-7-ethoxyisoflavone-3'-sulfonate. They were all characterized by ~1H NMR and IR. In addition, considering the biological functions of microelement and the potential effects that they combines with natural medicine, we obtained the isoflavonesulfonate derivatives, which are rubidium 5,7-dihydroxy-6,4'-dimethoxyisoflavone-3'-sulfonate, cesium 5,7-dihydroxy-6,4'-dimethoxyisoflavone-3 '-sulfonate, strontium 5,7-dihydroxy-6,4'-dimethoxyisoflavone-3'-sulfonate, copper 5-hydroxy-6,7,4'-trimethoxyisoflavone-3'-sulfonate, nickel 5,6,7,4'-tetrametroxyisoflavone-3 '-sulfonate.Lastly, irisolidone (1), kakkalidone (2), 5,6,7,4'-tetramethoxylisoflavone (3), 5-hydroxy-6,4'-dimethoxyl-7-ethoxyisoflavone (4), rubidium 5,7-dihydroxy-6,4'-di-methoxyisoflavone-3'-sulfonate (5), cesium 5,7-dihydroxy-6,4'-dimethoxyisoflavone-3'-sulfonate (6), strontium 5,7-dihydroxy-6,4'-dimethoxyisoflavone-3'-sulfonate (7), sodium 5-hydroxy-6,7,4'-trimethoxyisoflavone-3'-sulfonate (8), copper 5-hydroxy-6,7,4'-trimethoxyisoflavone-3'-sulfonate (9), nickel 5,6,7,4'-tetrametroxyisoflavone-3'-sulfonate (10) were determined by X-ray single-crystal diffraction analysis. Aromatic 7i—n stacking interactions and C-H-O, O-H-0 hydrogen bonds exist in the crystal structures of 1 and 2. The molecules of 3 are linked to a two-dimensional network structure by aromatic n-n stacking interactions and C-H-0 hydrogen bonds. However, the molecules of 4 are linked to 1-D columns by C—H-n interaction. 5 and 6 are isomorphic and possess similar crystal structures. Both of them are assembled to three-dimensional network structures through coordination of rubidium and cesium with oxygen atoms and hydrogen bonds from lattice water molecules. 5,7-dihydroxyl-6,4'-dimethoxyisoflavone-3'-sulfonate anion is not only the anion, but also the ligand of 7. Compound 8 is a dimeric centrosymmetric species. Each sodium atom is five-coordinated by oxygen atoms to form a distorted trigonal bipyramidal geometry. C-H'n interaction, hydrogen bonds, the coordinated interaction of metal and oxygen atoms, the electrostatic interactions between the cation and the anion assemble 7 and 8 into 3-D framework structures. In 9 and 10, the metal atoms are six-coordinated to water molecules. Combination of the hydrogen bonds generates fhe hydrophilic region, the hydrophobic region is built by n-n stacking interactions of isoflavone skeleton, the hydrophobic and hydrophilic region are bridged by the sulfo-group.The properties and species of isoflavones were enriched by structural modification of irisolidone. Studies on the crystal structures of isoflavone derivatives provided the theoretical foundations for developing and selecting high-technical new dugs.