Mangosteen Flavonoids And Metal Ions, Serum Albumin, And The Dna Interaction Studies

Mangostins have antibacterial, anti-inflammatory, antioxidant, antitumor biological and pharmacological activities, and also can inhibit HIV virus. Due to these biological and pharmacological activities, mangostins were paid much more attention in recent years. Our research focused on the interactions between mangostins and metal ions, serum albumins and DNA. The main contents and conclusions are as following:Firstly, Compared to the UV-Vis spectra of a-mangostin (α-MAG) andγ-mangostin (γ-MAG), the variation of UV-vis spectra of the complexes of theα-MAG andγ-MAG with metal ions, including Mg²⁺, Al³⁺ and Fe³⁺ et al, was investigated by UV-Vis spectrometry. Through measurement of the UV-Vis absorbance of the reaction solution containing different concentrations of the two MAGs and metal ions, the stoichiometric compositions of the complexes were determined according to the molar ratio method. Meanwhile the molar absorptivity and stablity constant of the complex were derived further. The results show that there are obvious changes in the UV-Vis spectra before and after the complexes of the two MAGs with metal ions formed. After the formation of the complexes of the two MAGs with metal ions, there occurs a bathchromic shift of the maximum absorption wavelength for the two MAGs, which may contribute to the coordination role of the hydroxyl group and keto group of the two MAGs. The stoichiometric compositions ([M]/[L]) of the complexes formed betweenα-MAG and Al³⁺, Fe³⁺ are 1: 1 and 1: 2, respectively. The stablity constants are 2.857×10⁶ and 1.527×10⁹, correspondingly. The stoichiometric compositions ([M]/[L]) of the complexes formed betweenγ-MAG and Mg²⁺, Al³⁺, Fe³⁺ and Cu²⁺ are 1: 2, 1: 1, 1: 1 and 1: 2, respectively. The stablity constants are 1.200×10⁹,2.227×10⁶,2.251×10⁶ and 2.311×10⁹, correspondingly. Secondly, The interaction betweenα-MAG and bovine serum albumin (BSA) or human serum albumin (HSA) was studied by fluorescence spectrometry. The results indicate that the mechanism of the quenching betweenα-MAG and BSA is a dynamic quenching process. The binding constants at 289K and at 300K are calculated to be 1.309×10⁵ and 6.776×10⁴ respectively, and the number of binding sites is about one. The binding locality is a distance 1.70 nm away from tryptophan residue based on Forster non-radiation energy transfer mechanism. The binding power is mainly the hydrogen bond and van der Waals force according to the thermodynamic parameters, the mechanism of the quenching betweenα-MAG and HSA is a dynamic quenching process. The binding constants at 298K and at 308K are calculated to be 3.327×10⁴ and 1.349×10⁴ respectively, and the number of binding sites is about one. The binding locality is a distance 1.82 nm away from tryptophan residue based on Forster non-radiation energy transfer mechanism. The binding power is mainly the hydrophobic force according to the thermodynamic parameters. Thirdly, The interactions betweenγ-MAG and deoxyribonucleic acid (DNA) were investigated in Tris-HCl buffer (pH=7.4) by fluorescence spectrometry and UV-vis absorption spectrometry, and were verified through viscosity method. The results indicate that DNA can obviously increase the fluorescence intensity ofγ-MAG, the part intercalative binding is the major model forγ-MAG and DNA, the ionic strength has an obvious effect on the interaction betweenγ-MAG and DNA.