Synthesis,characterization And Antioxidant Activity Of Chrysophanol Metal Complexes

The traditional Chinese medicine plants provided many compounds with pharmacological activities.Structural modification of these active components was an important research direction to find new drugs.Chrysophanol was an anthraquinone derivative,which was the main active component in Polygonum cuspidatum,rhubarb root and rhizome.Chrysophanol had many pharmacological activities,such as antioxidant,anticancer,neuroprotective,improving learning and cognitive impairment,myocardial protection and other pharmacological activities.Chrysophanol was easy to oxidize,which affected its antioxidant activity.It was of practical significance to modify the structure of chrysophanol to improve its antioxidant activity,so it was very important to study the structure modifycation of chrysophanol as the leading compound to improve its antioxidant activity.The study discussed mechanism of scavenging different free radicals perliminary,and obtain the metal complexes with better antioxidant activity.It provided a valuable practical basis for the development of high efficiency chinese medicine monomer drugs and their derivatives.The study was based on the synergistic effect of ligand structure and electronic effect on the metal complexes of native compound.The+2-valent metal complexes were synthesized by the coordination reaction of chrysophanol with metal ions Zn（Ⅱ）,Cu（Ⅱ）and Mn（Ⅱ）.The effects of reaction p H value were 6.0,6.5,7.0,7.5,8.0,return time were 1h,2h,3h,4h,5h,heating temperature were 20℃,30℃,40℃,50℃,60℃on the productivity of metal complexes were separately investigated by single factor experiment.The synthesis process of metal complexes was optimized by orthogonal test with reaction p H value of 6.5,7.0,7.5,return time of 3h,4h,5h,heating temperature of 30℃,40℃,50℃.The molecular weight of metal complexes was determined by mass spectrometry,and the contents of C,H,N and metal elements were obtained by elemental analysis and inductively coupled plasma mass spectrometry,so the molecular formula of metal complexes were calculated.The characteristic absorption peaks of chrysophanol and chrysophanol metal complexes were detected by ultraviolet visible spectrophotometry and infrared spectroscopy,then it can be inferred that the structure of metal complexes.The scavengi-ng activities of chrysophanol and metal complexes on 1,1-diphenyl-2-picr-ylhydrazyl（DPPH）,hydroxyl radical（OH·）and superoxide anion radical（O₂^-·）were studied by ultraviolet visible spectrophotometry,and ascorbic acid was used as positive control.The scavenging ability of chrysophanol and chrysophanol metal complexes on DPPH was observed by comparing the absorbance of DPPH solution at 517nm before and after adding free radical scavenger.Hydrogen peroxide was catalysed by Fe²⁺to form OH·,and salicylic acid will capture OH·to form colored substance with absorption at 510nm.The scavenging ability of chrysophanol and chrysophanol metal complexes on OH·was compared by comparing the absorbance changes of colored substances before and after adding free radical scavenger.By comparing the effects of chrysophanol and chrysophanol metal complexes on the self-oxidation rate of pyrogallol,the O₂^-·scavenging ability of chrysophanol before and after coordination was determined.The results showed that the effect of three factors on the synthesis of chrysophanol metal complexes was p H>heating temperature>return time.The optimum synthesis technology obtained by orthogonal test was as follows:the reaction p H value was 7.0,the return time was 4h,and the heating temperature was 40℃.It was showed that the peak shape of the absorption band of the conjugated system of benzene ring and quinone carbonyl group did not change after the coordination of chrysophanol by UV-vis,but a slight red shift was occurred,and a new absorption peak appeared at about 510nm.The infrared spectrum showed that the stretching vibration peak of hydroxyl group was weakened after the coordination of chrysophanol,and the stretching vibration peak of C=O was red shifted,and the stretching vibration peak of M（Ⅱ）-O appeared at about 530cm^-1.The content of Zn in chrysophanol-zinc was 11.57%.The content of Cu in chrysophanol-copper was 11.28%.The content of Mn in chrysophanol-manganese was 10.11%.There were determined by inductively coupled plasma mass spectrometry,The stoichiometric ratio of chrysophanol to metal ions was 2:1.The mass spectrometry determination of chrysophanol-zinc,chrysophanol-copper and chrysophanol-manganese[M+H]⁺was 573,572,562 respectively,and the molecular weight of chrysophanol-zinc,chrysophanol-copper and chrysophanol-manganese was 572,571,561.The content of C,H,N in chrysophanol-zinc was 62.36%,3.47%,0.47%respectively.The content of C,H,N in chrysophanol-copper was 62.71%,3.35%,0.71%respectively.The content of C,H,N in chrysophanol-manganese was 63.59%,3.42%,0.64%respectively.There were determined by elemental analysis,the molecular formula was C₃₀H₁₈O₈N₀-M（Ⅱ）[M=Zn,Cu,Mn].The results of DPPH,OH·and O₂^-·free radical scavenging experiments showed that the scavenging ability of chrysophanol and metal complexes to DPPH,OH·,O₂^-·free radical increased with the increase of the concentration in the certain range.There were significant differences between chrysophanol-zinc（P<0.01）,chrysophanol-copper（P<0.01）,chrysophanol-manganese（P<0.01）,vitamin C（P<0.01）and chrysophanol.The DPPH,OH·,O₂^-·free radical scavenging experiments showed that there was significant difference between different metal complexes（P<0.01）.The free radical scavenging effect of the three metal complexes was close to that of ascorbic acid.The antioxidant sequence was as follows:chrysophanol-zinc>chrysophanol-copper>chrysophanol-manganese>chrysophanol.The scavenging efficiency of the complexes was also affected by different active radicals.The order of scavenging ability of the complexes was DPPH>O₂^-·>OH·.In conclusion,three kinds of transition metal complexes with+2valence were synthesized by using chrysophanol as the leading compound through coordination reaction under the optimal process.The metal complexes formed a stable six membered ring structure by the coordination of O in 8-position phenol hydroxyl group and 9-O in carbonyl group with metal ions by UV-vis,IR,MS and elemental analysis.The scavenging ability of chrysophanol and metal complexes on DPPH,OH·,O₂^-·is concentration dependent,chrysophanol coordinated with metal elements had good antioxidant properties,and the antioxidant capacity of metal complexes varied with the types of metal elements.