Metal complex taking kaempferol as ligand and synthesis method thereof

Abstract

The invention relates to a metal coordination compound, in particular to a metal coordination compound with kaempferol as a ligand and a synthesis method of the metal coordination compound. The structural general formula of the metal complex taking kaempferol as the ligand is any one as follows: # imgabs0 # M is a metal ion. The invention also provides a synthesis method of the metal complex taking kaempferol as the ligand. The antioxidant activity of the kaempferol metal complex is higher than that of kaempferol.

Description

Technical Field

[0001] The invention relates to a metal coordination compound, in particular to a metal complex taking kaempferol as a ligand and a synthesis method thereof. Background Art

[0002] Kaempferol (3,4',5,7-tetrahydroxyflavone), also known as kaempferol, kaempferol-3, kaempferol, and kaempferol III, is mainly derived from the rhizome of the ginger plant kaempferol. It is widely found in vegetables and fruits and is one of the most abundant flavonoids in food. Kaempferol has multiple pharmacological activities such as antioxidant, anti-inflammatory, anti-cancer and antibacterial. In addition, its semi-synthetic process is simple to operate and low in cost.

[0003] Metal ions are an important part of the life metabolism process. Cu, Zn, and Fe are essential trace elements for the human body and are also the most used elements. Flavonoids are effective metal ion chelators with unique electron-rich and highly conjugated chemical structures. Regulating the homeostasis of metals may play an important role in the biological activity of flavonoids.

[0004] The metal ion complexes of active ingredients of traditional Chinese medicine have been the focus of research in recent years. More and more studies have also shown that the synergistic effect between the effective active ingredients of traditional Chinese medicine and trace elements can enhance the original activity or produce new physiological activity. The complexes formed by chelating flavonoids with metal ions not only have higher physiological activity than flavonoids, but also have reduced toxicity. Therefore, the study of kaempferol metal complexes has opened up a new path for the further development and utilization of the natural drug ingredient kaempferol and the research and development of new drugs. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a metal complex taking kaempferol as a ligand and a synthesis method thereof.

[0006] In order to solve the above technical problems, the present invention provides a metal complex with kaempferol as a ligand, the general structural formula of which is any of the following:

[0007]

[0008] M is a metal ion.

[0009] As an improvement of the metal complex with kaempferol as a ligand of the present invention: the metal ion is any of the following main group metal ions, transition metal ions, and rare earth metal ions.

[0010] As a further improvement of the metal complex with kaempferol as a ligand of the present invention:

[0011] In general formula 1: M = Cu, Fe;

[0012] In general formula 2: M = Zn.

[0013] The present invention also provides a method for synthesizing a metal complex using kaempferol as a ligand, comprising the following steps:

[0014] 1) Add kaempferol to anhydrous ethanol, protect under inert gas (such as nitrogen), slightly heat (40±5° C.) to completely dissolve kaempferol, then adjust pH=8, react at 40° C. for 0.5 h, and obtain an ethanol solution of kaempferol;

[0015] 2) dissolving or dispersing the metal salt in anhydrous ethanol, and then dropping (slowly dropping, i.e., the dropping time is about 10±2 minutes) into the ethanol solution of kaempferol, stirring continuously during the dropping process to generate a precipitate;

[0016] The molar ratio of the metal salt to kaempferol is 1 to 2:1;

[0017] After the addition is completed, the mixture is heated under reflux until no new precipitation is generated. The supernatant is removed after centrifugation, and the precipitate is washed with water and anhydrous ethanol in sequence, twice respectively, and dried under vacuum at 45±5° C. to constant weight to obtain a metal complex with kaempferol as a ligand.

[0018] As an improvement of the synthesis method of the metal complex with kaempferol as a ligand of the present invention:

[0019] The metal is any of the following: copper (II), zinc (II), iron (III);

[0020] The anion sources of the metal salt are acetate, chloride and sulfate ions.

[0021] As an improvement of the synthesis method of the metal complex with kaempferol as a ligand of the present invention: the heating reflux reaction time is 4 to 8 hours.

[0022] As an improvement to the synthesis method of the metal complex with kaempferol as a ligand of the present invention: the heating reflux temperature is 40 to 80°C.

[0023] The beneficial effects of the present invention are:

[0024] The synthesis method provided by the present invention is simple and easy to operate. After kaempferol forms a metal complex with metal ions, it can not only enhance the original biological activity, but also supplement more metal elements that are beneficial to the body. The present invention uses three antioxidant experimental methods to evaluate the scavenging DPPH and ABTS free radicals and the total antioxidant capacity of kaempferol and its metal complex as an example. The experimental results show that the antioxidant activity of the kaempferol metal complex is stronger than that of kaempferol. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The specific implementation modes of the present invention are further described in detail below with reference to the accompanying drawings.

[0026] Figure 1 This is the UV image of kaempferol;

[0027] Figure 2 This is the UV image of kaempferol-copper;

[0028] Figure 3 This is the UV image of kaempferol-zinc;

[0029] Figure 4 is the UV image of kaempferol-iron;

[0030] Figure 5 This is the infrared image of kaempferol;

[0031] Figure 6 This is the infrared image of kaempferol-copper;

[0032] Figure 7 This is the infrared image of kaempferol-zinc;

[0033] Figure 8 This is the infrared image of kaempferol-iron. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0035] The kaempferol metal complex of the present invention has a super delocalization degree and a large π bond conjugated system in the structure of kaempferol, and the carbonyl oxygen and hydroxyl group in the molecule can chelate with various metal ions to form a stable complex, and its structure is shown below:

[0036]

[0037] Example 1: Preparation of kaempferol-copper complex, the following steps are carried out in sequence:

[0038] 1) Add 2 mmol of kaempferol (0.57 g) to 15 mL of anhydrous ethanol, under nitrogen protection, and stir continuously at 40° C. to completely dissolve the kaempferol; then add an appropriate amount of solid sodium hydroxide, adjust the pH to 8, and react at 40° C. for 0.5 h to obtain an ethanol solution of kaempferol;

[0039] 2) Dissolve 1 mmol of copper chloride dihydrate (0.17 g) in 15 mL of anhydrous ethanol, slowly add (addition time is about 10 minutes) to the ethanol solution of kaempferol, stir and reflux at 60°C for 4 hours to completely precipitate (i.e. no new precipitate is generated). After centrifugation, remove the supernatant, wash the precipitate twice with anhydrous ethanol and water respectively, and vacuum dry at 45°C to constant weight to obtain about 0.5405 g of kaempferol-copper complex.

[0040] The structural formula of kaempferol-copper complex is: Cu(Kae)2(H2O)2.

[0041] Example 2: Preparation of kaempferol-zinc complex, the following steps are carried out in sequence:

[0042] 1) Add 1 mmol of kaempferol (0.57 g) to 15 mL of anhydrous ethanol, under nitrogen protection, and stir continuously at 40° C. to completely dissolve the kaempferol; add an appropriate amount of sodium hydroxide, adjust the pH to 8, and react at 40° C. for 0.5 h to obtain an ethanol solution of kaempferol;

[0043] 2) Dissolve 1 mmol zinc acetate dihydrate (0.44 g) in 15 mL anhydrous ethanol, slowly add to the ethanol solution of kaempferol, stir and reflux at 80°C for 8 hours to completely precipitate. After centrifugation, remove the supernatant, wash the precipitate with anhydrous ethanol and water twice, respectively, and vacuum dry at 45°C to constant weight to obtain about 0.5004 g of kaempferol-zinc complex.

[0044] The structural formula of kaempferol-zinc complex is: Zn(Kae)(H2O)2.

[0045] Example 3: Preparation of kaempferol-iron complex, the following steps are carried out in sequence:

[0046] 1) Add 1 mmol of kaempferol (0.57 g) to 15 mL of anhydrous ethanol, under nitrogen protection, and stir continuously at 40° C. to completely dissolve the kaempferol; add an appropriate amount of sodium hydroxide, adjust the pH to 8, and react at 40° C. for 0.5 h to obtain an ethanol solution of kaempferol;

[0047] 2) Dissolve 1 mmol of anhydrous ferric chloride (0.32 g) in 15 mL of anhydrous ethanol, slowly add it to the ethanol solution of kaempferol, stir and reflux at 70°C for 4 hours to completely precipitate it. After centrifugation, remove the supernatant, wash the precipitate twice with anhydrous ethanol and water, and vacuum dry at 45°C to constant weight to obtain about 0.674 g of kaempferol-iron complex.

[0048] The structural formula of kaempferol-iron complex is: Fe(Kae)2(H2O)2.

[0049] Experiment 1, Structure Identification of Kaempferol Metal Complexes Obtained from Examples 1 to 3

[0050] 1. UV spectroscopy characterization

[0051] Weigh appropriate amounts of kaempferol and kaempferol metal complex and dissolve them in anhydrous ethanol to prepare 1.0×10 - 5 mol / L sample solution. Using anhydrous ethanol as a reference, transfer the sample solution into a cuvette and scan in the range of 250-550nm. The UV-visible absorption spectrum of the sample solution is shown in Table 1.

[0052] Table 1. UV spectra of kaempferol and its complexes

[0053]

[0054] The ultraviolet absorption spectra of kaempferol and kaempferol metal complexes were measured in the range of 250-550nm. Kaempferol has two absorption peaks at 267nm and 368nm. As shown in Table 1 above, after the formation of the three complexes, band I moved about 0-14nm, and band II moved about 50-120nm, indicating that the kaempferol metal complex is coordinated through ring C. Compared with kaempferol, the absorption peak of kaempferol metal complex moves to the long wavelength region. This is caused by the conjugated system formed between the metal ions and kaempferol, so red shift occurs in these two absorption bands. The metal ions form new rings with 3-OH and 4-C=O in kaempferol, which increases the conjugated system of the entire molecule, resulting in an increase in the degree of electron delocalization and a decrease in the electron transition energy.

[0055] 2. Infrared spectroscopy characterization

[0056] The KBr tablet method was used and infrared spectroscopy was used at 500-4000cm -1 Kaempferol and its complexes were scanned within the range, and the experimental results are shown in Table 2.

[0057] Table 2. Main infrared data of kaempferol and kaempferol metal complexes (cm -1 )

[0058]

[0059] From Table 2 above, we can see that the carbonyl vibration frequency υ(C=O) of kaempferol is 1655cm -1 , after forming the complex, it appears at 1599cm -1 -1635cm -1 It can be seen that a coordination bond is formed between 4-C=O of kaempferol and the metal ion, causing the electrons to move from the center of the bond to the oxygen atom, thereby reducing the bond (C=O) electron density. Therefore, the absorption band of the carbonyl stretching vibration moves to a low frequency, the complex forms a new ring, and the conjugation effect is enhanced, so that the π bond υ (C=C) of the complex benzene ring increases from 1615cm -1 The complex shifts to the low wave number direction. -1 The υ(MO) vibration appears around 1165cm, indicating that the metal ion and the ligand are chelated. The υ(COC) vibration frequency in the ligand and the complex is 1165cm -1 -1172cm -1 The little change in position indicates that it does not participate in the reaction.

[0060] Experiment 2

[0061] 1. DPPH free radical scavenging experiment

[0062] Weigh 4 mg DPPH (1×10 -5 mol) was dissolved in an appropriate amount of anhydrous ethanol and diluted to 20 mL to prepare a 500nmol / mL DPPH solution. Weigh an appropriate amount of sample (kaempferol, kaempferol metal complex), add anhydrous ethanol to prepare a test solution with a concentration of 500nmol / mL, and then dilute to test sample solutions with concentrations of 250, 125, 62.5, and 31.3nmol / mL. Mix 2mL of DPPH solution with 2mL of sample solution, place at 37°C in the dark for 30 minutes, and measure the absorbance A at 517nm. s The above experiment was repeated three times with Vc as the control.

[0063] DPPH free radical scavenging rate calculation formula: scavenging rate = [A o -(A s -A y )] / A o ×100(A y Represents the absorbance of 2 mL sample solution and 2 mL anhydrous ethanol; A o Represents the absorbance of 2mL anhydrous ethanol solution and 2mL DPPH solution; A s Represents the absorbance of 2mL sample solution and 2mL DPPH solution)

[0064] Table 3. Experimental results of scavenging DPPH free radicals

[0065]

[0066]

[0067] The experimental results showed that the scavenging ability of kaempferol-copper and kaempferol-iron was stronger, significantly higher than that of kaempferol and VC. The scavenging ability of kaempferol-zinc was weaker, but it had good scavenging activity. 50 The smaller the value, the stronger the antioxidant activity. Comparison of IC values ​​of kaempferol and its complexes in scavenging DPPH free radicals 50 The order of scavenging ability is kaempferol-copper > kaempferol-iron > kaempferol-manganese > Vc > kaempferol > kaempferol-zinc.

[0068] 2. ABTS free radical scavenging experiment

[0069] Weigh 30 mg (5.5 × 10 -5mol) ABTS free radical powder was dissolved in 8mL distilled water to obtain 7.0mmol / L ABTS aqueous solution. Weigh 10mg K2S2O8 and dissolve in 15mL distilled water. Mix the above two solutions in equal volumes to prepare ABTS stock solution and place it in a dark place at room temperature for 12-16h for use. Dilute with anhydrous ethanol before use until the absorbance at 734nm is within the range of 0.7±0.02, which can be used as ABTS+ working solution.

[0070] Prepare a 125 nmol / mL sample (kaempferol, kaempferol metal complex) solution and dilute it with anhydrous ethanol to a concentration gradient of 62.5, 31.3, 15.6, 7.8, and 3.9 nmol / mL. Pipette 100 μL of the sample solution and 100 μL of the ABTS+ working solution, shake evenly, react at room temperature in the dark for 6 minutes, and measure its absorbance A at 734 nm. 样品组 The above experiment was repeated three times with Vc as the control.

[0071] ABTS free radical scavenging rate: scavenging rate = 1-[(A 样品组 -A 背景组 ) / A 空白组 ]×100(A 样品组 Represents 100 μL sample solution and 100 μL ABTS+ working solution; A 背景组 Represents 100 μL sample solution and 100 μL anhydrous ethanol; A 空白组 represents 100 μL of anhydrous ethanol and 100 μL of ABTS+ working solution)

[0072] Table 4. Results of ABTS free radical scavenging experiment

[0073]

[0074]

[0075] IC 50 The smaller the value, the stronger the antioxidant activity. The experimental results show that kaempferol-copper, kaempferol-zinc, and kaempferol-iron all have high scavenging ability, which is significantly higher than kaempferol and VC. Comparison of IC values ​​of kaempferol and its complexes in scavenging ABTS free radicals 50 The order of scavenging ability is kaempferol-copper > kaempferol-zinc > kaempferol-iron > kaempferol > Vc.

[0076] 3. Total Antioxidant Capacity Test

[0077] Take 1.0 mL of Vc and sample (kaempferol, kaempferol metal complex) solution (the concentrations are 4 kinds of concentrations described in Table 3), add 2.5 mL of sodium phosphate buffer and 2.5 mL of 1% potassium ferricyanide solution and mix well, and react in a 50°C water bath for 20 minutes. Then cool the reaction solution to room temperature for 10 minutes, add 2.5 mL of 10% trichloroacetic acid, and then centrifuge at 3000r / min for 10 minutes. Take 2.5 mL of supernatant, add 2.5 mL of distilled water, 0.5 mL of 0.1% ferric chloride solution, mix, react in the dark at room temperature for 10 minutes, and measure the absorbance A1 of the sample solution at 700nm. Take Vc as the control and repeat three times in parallel.

[0078] Absorbance = A1-A0 (A1 represents the absorbance of the sample solution; A0 represents the absorbance of the blank control solution)

[0079] Table 5. Total antioxidant capacity test results

[0080]

[0081] As the concentration of the sample increases, the absorbance value also gradually increases, indicating that the total antioxidant capacity of kaempferol, its metal complexes and vitamin C is positively correlated with the concentration of the sample. The greater the absorbance, the stronger the total antioxidant capacity of the solution. The experimental results show that the total antioxidant capacity of kaempferol-iron and kaempferol-zinc is poorer than that of kaempferol, while the total antioxidant capacity of kaempferol-copper is stronger. The order of the total antioxidant capacity of kaempferol and its complexes is kaempferol-copper>kaempferol>kaempferol-zinc>kaempferol-iron>Vc.

[0082] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A metal complex with kaempferol as a ligand, characterized in that Its general structural formula is any of the following: M is a metal ion.

2. The metal complex with kaempferol as a ligand according to claim 1, characterized in that: The metal ion is any of the following main group metal ions, transition metal ions, and rare earth metal ions.

3. The metal complex with kaempferol as a ligand according to claim 1 or 2, characterized in that: In general formula 1: M = Cu, Fe; In general formula 2: M = Zn.

4. A method for synthesizing a metal complex with kaempferol as a ligand, characterized in that The following steps are involved: 1) Add kaempferol to anhydrous ethanol, under the protection of inert gas, slightly heat to completely dissolve the kaempferol, then adjust the pH to 8, react at 40° C. for 0.5 h, and obtain an ethanol solution of kaempferol; 2) dissolving or dispersing the metal salt in anhydrous ethanol, and then adding dropwise to the ethanol solution of kaempferol, stirring continuously during the dropping process to generate a precipitate; The molar ratio of the metal salt to kaempferol is 1 to 2:1; After the addition is completed, the mixture is heated under reflux until no new precipitation is generated. The supernatant is removed after centrifugation, and the precipitate is washed with water and anhydrous ethanol in sequence, twice respectively, and dried under vacuum at 45±5° C. to constant weight to obtain a metal complex with kaempferol as a ligand.

5. The method for synthesizing a metal complex with kaempferol as a ligand according to claim 4, characterized in that: The metal is any of the following: copper (II), zinc (II), iron (III); The anion sources of the metal salt are acetate, chloride and sulfate ions.

6. The method for synthesizing a metal complex with kaempferol as a ligand according to claim 5, characterized in that: The heating reflux reaction time is 4 to 8 hours.

7. The method for synthesizing a metal complex with kaempferol as a ligand according to claim 6, characterized in that: The heating reflux temperature is 40-80°C.

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