Preparation And DNA Cleavage Activity Of Quercetin Metal Complexes Based On The Theory Of Coordination Chemistry Of Traditional Chinese Medicine

According to the theory of traditional Chinese medicine complex,the medicinal ingredients in traditional Chinese medicine may be organic components or trace elements,and may be metal complexes formed by the reaction of Chinese medicine in the process of boiling.At present,there are two main methods for the study of metal complexes in traditional Chinese medicines:one is to prepare a metal complex of the monomer component of traditional Chinese medicine by chemical synthesis,and then to study its structure and activity;the other is to treat traditional Chinese medicine water.The morphology of the metal ions in the decoction was analyzed to demonstrate the presence of the metal complex.These two related research methods have failed to solve the problems of which organic components in Chinese medicine can form complexes with which metal ions,what structure of newly formed complexes,and what role they play in the treatment of diseases.Quercetin is one of the most widely distributed flavonoids in nature.It has many biological activities such as anti-oxidation,anti-cancer,anti-bacterial and anti-inflammatory.Its structure contains 5 phenolic hydroxyl groups and 1 carbonyl group.The ion undergoes a coordination reaction,and the activity of the formed quercetin-metal complex is significantly higher than that of quercetin.However,a large number of reported methods for the preparation of complexes are basically carried out in an alkaline alcohol solution（methanol or absolute ethanol）,which is very different from the traditional Chinese medicine extraction process,and at present,there are few reports on the separation of metal complexes from traditional Chinese medicines.Then,under the traditional Chinese medicine extraction process,can we obtain a quercetin-metal complex with a certain biological activity?In this paper,we first studied the ability of quercetin to form complexes with five kinds of metal trace elements commonly found in traditional Chinese medicine under the traditional Chinese medicine decoction process.Secondly,The high performance liquid chromatography（HPLC）was used to analyze the samples of Chinese herbal medicine aqueous extracts dissolved with methanol and 20%formic acid-methanol,respectively,and The possibility of the presence of quercetin-metal complex in Chinese herbal decoction was discussed.Then,ESI-TOF MS was used to detect the reaction products of quercetin and five kinds of metal trace elements commonly found in traditional Chinese medicine in hot water,and the proportion and structure of quercetin-metal complex formed in the reaction were estimated.Finally,the DNA cleavage activity and DPPH free radical scavenging activity of quercetin-metal complexes were studied.The main research contents and research results of the thesis are as follows:（1）The ability of quercetin to form complexes with five metal ions.Quercetin reacts with five essential metal elements(Mg²⁺,Ca²⁺,Fe³⁺,Cu²⁺,Zn²⁺)under the traditional Chinese medicine extraction process.The content of ligands before and after the reaction is quantitatively detected by high performance liquid chromatography.The optimum reaction conditions（reaction temperature,reaction time,reaction solvent and stoichiometric ratio）of the complex synthesis reaction were obtained.Under the optimal synthesis conditions,the ability of quercetin to form complexes with five metal ions was investigated.The experimental results show that the optimum conditions for the formation of complexes of quercetin with metal ions are:reaction temperature 95°C,reaction time 3 h,reaction solvent volume 20mL,molar ratio of ligand to metal ion 2:1.In water decoction conditions,Cu²⁺is most likely to form complexes with quercetin,followed by Fe³⁺,while,Mg²⁺,Ca²⁺and Zn²⁺have poorer complexing ability.（2）Discussion on the possibility of quercetin-metal complex in Chinese herbal decoction.Taking Crataegus pinnatifida Bge.,Houttuynia cordata Thunb.,Dendranthema morifolium（Ramat）Tzvel.cv.Gongju and Viola yedoensis Makino as research objects,the samples of four Chinese herbal medicine aqueous extracts were dissolve by methanol and 20%formic acid-methanol respectively,and when using20%formic acid-methanol as solvent,the peak area of??quercetin in the aqueous extracts of Crataegus pinnatifida Bge.,Dendranthema morifolium（Ramat）Tzvel.cv.Gongju,Houttuynia cordata Thunb and Viola yedoensis Makino increased by 37.55%,207.35%,378.53%and 234.68%,respectively,compared with methanol.The experimental results show that quercetin forms a complex with the metals trace elements of Chinese medicine during water decoction.（3）ESI-TOF-MS analysis of quercetin-metal complex.The quercetin was reacted with five kinds of metal trace elements commonly found in plants such as calcium,magnesium,zinc,iron（III）and copper in 95°C water,and the supernatant after the reaction was detected by ESI-TOF-MS.It is shown that quercetin can form complexes with Ca²⁺,Mg²⁺,Zn²⁺and Cu²⁺metal ions at the ratio of 2:1,3:1 and 3:2.However,after reacting with Fe³⁺at 95°C,not only the quercetin-iron（III）complex be formed at the ratio of 2:1 and 3:1,but also a small amount of Fe²⁺will be formed,and the complex of quercetin-iron（II）will be formed at the ratio of 2:1 and 3:1.（4）Study on DNA cleavage activity of quercetin-metal complex.The cleavage effect of quercetin,metal salt and quercetin metal complex on plasmid pBR 322 DNA was studied.The results of DNA cleavage experiments showed that quercetin and Cu²⁺did not cleave when acting alone on DNA,or the cleavage was weak,but the complex formed by the reaction of quercetin with Cu²⁺had significant DNA cleavage activity,and the cleavage showed Significant time and concentration dependencies.The effect of the reaction product of quercetin and Cu²⁺on DNA is an oxidation mechanism.（5）DPPH free radical scavenging activity of quercetin-metal complexes.The scavenging activity of the products formed by the reaction of five metal ions with quercetin in hot water was studied.The results showed that the free radical scavenging activity of the products of the five metal ions and quercetin in hot water was lower than that of quercetin.Free radical scavenging activity.Relatively speaking,quercetin-copper has the strongest free radical scavenging activity,and quercetin-zinc has the weakest free radical scavenging activity.