Basic Chemistry Research Of Several Important Bioactive Substances In Ginkgo Biloba

There are many kinds of active substances which can coordinate with metals in Ginkgo biloba,but no definite theory about the specific mode of action in human body and whether it will affect the steady-state balance of metals in human body.In order to provide a chemical basis for the action of flavonoids in human body,in this paper,eight kinds of single component flavonoids were isolated from Ginkgo biloba leaves,and a series of basic chemical studies were carried out on the coordination of flavonoids in Ginkgo biloba with metals.The main work and achievements of this paper include:(1)Quercetin,kaempferol and isorhamnetin were isolated and coordinated with Fe³⁺,Cu²⁺,and Zn²⁺to form a complex,the coordination reaction conditions were optimized and the yield of complexes was 61.7-84.4%,its coordination number was two,coordination point was located at 3-OH and 4-C=O.DPPH and ABTS free radical scavenging tests showed that the free radical scavenging activity of the three flavonoid aglycones was increased after coordination with Cu²⁺and Zn²⁺.Quercetin-Cu complex has the highest radical scavenging activity,its IC₅₀ value of scavenging DPPH and ABTS was 1.10.?g/m L,0.66?g/m L;The stability constant log K of the complex obtained at p H=7.2 and 36.5°C was determined by Job's method and isochromatic point continuous change method.Quercetin-Fe complex(16.6)was the highest,and isorhamnetin-Zn(7.29)was the lowest.Based on this calculation,the maximum content of metal complexes excluding other compounds in the human intestine,was157.8?319.3 mg and 96.2?369.3 mg in body fluids,if Ginkgo biloba extract is used in daily life,the highest content of flavonoid metal complex in intestine and body fluid is 189.0?321.9 mg and 114.8?391.0 mg.(2)Five kinds of biflavonoids were isolated and prepared,including amentoflavone,bilobetin,ginkgetin,isoginkgetin and sciadopitysin.The separation conditions of the ginkgetin isomers were discussed.Then optimized the reaction conditions to get four kinds of biflavones which coordinated with Fe³⁺,Cu²⁺,Zn²⁺.The ligands were 1(Cu²⁺,Zn²⁺)or 2(Fe³⁺),and the coordination sites were located at 4'-C=O and 5'–OH or 5''-OH,4''-C=O.Among the five biflavones and their complexes,DPPH and ABTS free radical scavenging tests showed that complex with metals could significantly enhance the antioxidant activity of the compounds,amentoflavone has the highest scavenging activities with IC₅₀ of 23.5?g/m L and 3.8?g/m L.(3)The method of metal coordination desorption was established to purify the flavonoids in Ginkgo biloba.The optimal purification conditions were as follows,2.0g of the crude extract was dissolved in 200 m L of ethanol,0.4 g of copper sulfate pentahydrate was added,controlled p H=7,and the amount of EDTA required was 1.0g.The content of flavonol glycoside increased from 23.8%to 58.7%,the recovery rate was 74.6%,the total flavone content increased from 37.4%to 78.3%,and the recovery rate was 67.4%.The purity of biflavones increased from 37.7%to 82.5%and the recovery rate was 72.1%.(4)The flavonoid metal complex in the residue was extracted by EDTA decomposition,and the content of the complex flavonoids in the residue was 2.1 mg/g,and the content of other forms of the complex metal elements was 27.5 mg/g.