Efficient and stable cis-isomerization method for lycopene

Abstract

Disclosed in the present invention is an efficient and stable cis-isomerization method for lycopene. The method comprises using a bimetallic metal-organic framework material as a catalyst to catalyze the cis-isomerization of lycopene. In the method, confined water molecules can also be added to a reaction system as a catalytic medium to efficiently catalyze the isomerization of lycopene. The catalyst attacks and activates a conjugated double bond of all-trans-lycopene in an electron-rich environment, leading to rotation to form a corresponding configuration, and the confined water molecules serve as an electron transfer medium to accelerate the ability of the trans-lycopene to lose electrons, forming a lycopene free radical as an isomerization intermediate product, and further improving the isomerization yield of cis-lycopene. The method is green and efficient, increasing the isomerization efficiency of cis-lycopene up to 82.2%, and under the process condition, lycopene has a higher retention rate of 90.3%. The method is green and efficient and has great prospects for application.

Description

A highly efficient and stable method for cis-isomerization of lycopene Technical Field

[0001] This invention relates to a highly efficient and stable method for the cis-isomerization of lycopene. Background Technology

[0002] Over 90% of lycopene in natural plants is in the all-trans configuration, which has lower bioavailability and antioxidant activity compared to the cis configuration. The 5-cis isomer, in particular, exhibits higher bioactivity and stability, making it a promising candidate for development and application in the food, nutritional, and pharmaceutical industries. These characteristics result in higher added value for lycopene products with a high proportion of cis isomers in the market. Therefore, developing highly selective, efficient, and stable cis isomerization technologies is crucial for preparing high-value-added nutritional fortifiers.

[0003] Common methods for lycopene cis isomerization include thermal isomerization, photo-induced isomerization, catalytic isomerization, microwave isomerization, and electrochemical isomerization. Thermal / photo-induced isomerization, which promotes the conversion of lycopene from the all-trans isomer to the cis isomer through direct heating, is currently the most commonly used isomerization method in research. Especially during heat treatment, increased temperature and prolonged processing time increase the proportion of cis isomers, but also cause significant degradation of lycopene. Therefore, isomerization strategies are generally limited by inherent problems such as low conversion efficiency (typically <50%) and high reversibility.

[0004] In existing technologies, heterogeneous catalysts such as I-TiO2 and Cu-MCM-41 are used for the isomerization reaction of lycopene, but these reactions typically require pure organic solvents such as dichloromethane and acetone. These systems not only have low reaction rates and limited product yields (e.g., approximately 50% yield after 6 hours), but the organic solvents also induce lycopene degradation, leading to product loss, with degradation rates reaching up to 30%. To improve reaction efficiency, recent studies have attempted to introduce a small amount of free water into the organic medium, utilizing water molecules to lower the reaction energy barrier and thus improve isomerization efficiency. For example, adding 2.5% water to an acetone system catalyzed by FeCl3 or AlCl3 can increase the total cis-lycopene yield by up to five times. Furthermore, the Fe2(SO4)3–free water composite catalytic system forms [Fe(H2O)6]... 3+ Hydrated ions reconstruct the hydrogen bond network and enhance the electronic coupling between metal ions and the lycopene π system, increasing the cis-isomerization efficiency to 65%. However, the coordination stability of hydrated ions in this system is insufficient, and lycopene self-aggregates due to hydrophobic interactions, forming a layered structure that hinders effective mass transfer, resulting in a final product retention rate of only 52%. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a highly selective, efficient and stable method for the cis-isomerization of lycopene.

[0006] Technical solution: This invention discloses a highly efficient and stable cis-isomerization method for lycopene, which uses a bimetallic organic framework material as a catalyst to catalyze the cis-isomerization of lycopene.

[0007] The bimetallic organic framework material is a zirconium-based organic framework material doped with a transition metal material, with an octahedral crystal structure formed by coordination of the organic ligand tetrafluoroterephthalic acid and metal ions. The metal ions are zirconium ions, copper ions, zinc ions, or iron ions. Among the metal ions, copper ions, zinc ions, or iron ions are doped metal ions, and the molar amount of the doped metal ions is 20-50% of the total molar amount of metal ions.

[0008] The zirconium-based organic framework material includes UIO-66 or MOF-801, and the bimetallic organic framework material is Zn. 1 / 5 -UIO-66、Zn 1 / 4 -UIO-66、Zn 1 / 2 -UIO-66、Cu 1 / 5 -UIO-66、Cu 1 / 4 -UIO-66、Cu 1 / 2 -UIO-66、Fe 1 / 5 -UIO-66、Fe 1 / 4 -UIO-66、Fe 1 / 2 -UIO-66 or Cu-MOF-801.

[0009] The method for preparing the bimetallic organic framework material includes the following steps:

[0010] (1) Dissolve zirconium oxynitrate, copper nitrate trihydrate, zinc nitrate hexahydrate, and ferric nitrate nonahydrate in a solution of methanol and formic acid, respectively, and stir to dissolve to obtain a mixed solution. The molar ratio of zirconium oxynitrate to copper nitrate trihydrate, zinc nitrate hexahydrate, and ferric nitrate nonahydrate is 4:1-1:1, and the volume ratio of methanol to formic acid is 5:1-2:1.

[0011] (2) Add tetrafluoroterephthalic acid to the mixed solution, stir, and keep the temperature at 30℃~50℃ for 10~14h.

[0012] (3) The obtained solid material is centrifuged and washed, and then vacuum dried to obtain a bimetallic organic framework material; the washing agent is methanol, the centrifugation speed is 3000 rpm / min, the centrifugation time is 10 min, and the centrifugation temperature is 10℃~20℃; the vacuum drying temperature is 45℃~60℃, the time is 8~10 h, and the drying pressure is -0.09~-0.1 MPa.

[0013] The method of the present invention specifically involves taking bimetallic organic framework material and lycopene solution separately, stirring, and heating in a hot reflux water bath while avoiding light; the lycopene mixed solution after the reaction is filtered to obtain the product. The ratio of the amount of bimetallic organic framework material to lycopene is 4:1-2:1, the heating temperature is 25-50℃, the heating time is 0.5-2h, magnetic stirring is used, and the reaction is carried out in a hot reflux water bath while avoiding light.

[0014] The method of the present invention dissolves trans-lycopene in an organic solvent and can also add a catalytic medium to form a catalytic system for the preparation of lycopene via cis-isomerization. The catalytic medium is confined water, and the volume percentage of the catalytic medium in the catalytic system is 1-2%.

[0015] The catalytic medium is confined water, which is water molecules bound in the cavities and channels of the porous structure of Cu-MOF-801. The water molecules are confined in molecular or nanoscale space to form a confinement effect. The volume percentage of the confined water in the catalytic system is 1-2%.

[0016] The preparation method of the bimetallic catalyst includes the following steps:

[0017] (1) Dissolve trans-lycopene in acetone, add bimetallic organic framework material to the reaction system, add catalytic medium to the reaction system to form a catalytic system. Due to the confinement effect of the synthesized transition metal-based catalyst, water molecules can be precisely controlled through coordination. The water molecules in the catalytic medium are in the form of confined water molecules.

[0018] (2) The above catalytic system was subjected to a water bath and heated with stirring;

[0019] (3) After catalysis, the solution is centrifuged to recover the catalyst precipitate, thus obtaining cis-lycopene acetone solution, completing the isomerization of lycopene.

[0020] In step (1), the bimetallic organic framework material is a Cu-doped MOF-801 nanomaterial, and the concentration of the bimetallic organic framework material is 0.5 mg / mL.

[0021] In step (2), the heating temperature is 30-40℃ and the stirring time is 1h.

[0022] The bimetallic catalyst is prepared by dissolving fumaric acid, zirconium oxychloride octahydrate and copper nitrate trihydrate in a mixed solution of DMF and formic acid, stirring thoroughly to obtain a mixed solution; reacting the mixed solution at high temperature, cooling and washing at room temperature after the reaction is completed to obtain a precipitate; and drying the precipitate under vacuum.

[0023] The reaction mixture consisted of 4–6 mmol of fumaric acid, 3.54 mmol of zirconium oxychloride octahydrate, 1–5 mmol of copper nitrate trihydrate, and a volume ratio of DMF to formic acid of (18–20 mL: 5–8 mL). The reaction was carried out at a high temperature of 120–130 °C for 5–6 h. The drying temperature was 50–60 °C for 7–8 h, and the vacuum drying pressure was -0.1 MPa.

[0024] The specific method for preparing the bimetallic organic framework material is as follows:

[0025] (1) Dissolve 5 mmol of fumaric acid, 3.75 mmol of zirconium oxychloride octahydrate and 1.25 mmol of copper nitrate trihydrate in a mixed solution of 20 mL of DMF and 7 mL of formic acid, and then stir the mixed solution thoroughly.

[0026] (2) Transfer the above mixed solution to a high-pressure reactor and place it in an oven (130℃, 6h). After the reaction is complete, cool it to room temperature. Then wash it four times by centrifugation with DMF and methanol.

[0027] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50℃, 8h). The vacuum pump is turned on to evacuate and dry to a pressure of -0.1MPa, thus obtaining Cu-doped MOF-801 transition metal-based nanomaterials.

[0028] Invention Principle: The efficient and stable lycopene isomerization method of this invention, specifically the method for promoting cis-isomerization of lycopene, utilizes a transition metal (Cu, Fe)-doped bimetallic organic framework material as a catalyst to achieve the isomerization of all-trans lycopene, thereby enhancing its bioactivity. This catalyst has the ability to accept electron pairs and is a Lewis acid. All-trans lycopene, rich in conjugated double bonds, creates an electron-rich environment, making it susceptible to attack by electrophiles, thus forming a Lewis base. Therefore, the conjugated double bonds of all-trans lycopene are easily activated by the catalyst, rotating into the corresponding configuration. The appropriate doping of Cu and Fe enhances the electron-accepting ability of the material, allowing the bimetallic organic framework material Cu... 1 / 4@UIO-66 and Fe 1 / 2 @UIO-66 exhibits the best catalytic effect. Therefore, Cu 1 / 4 @UIO-66 and Fe 1 / 2@UIO-66 outperforms undoped, zinc-doped, and other doped UIO-66 in terms of retention rate, total isomerization rate, and 5-position isomerization rate, making it more environmentally friendly and efficient.

[0029] Furthermore, a transition metal-confined water synergistic catalytic approach was adopted for lycopene isomerization. The presence of water molecules was controlled by a transition metal-based catalyst, transforming free water into nano-confined water. These confined water molecules act as electron transfer mediators in the trans-lycopene isomerization pathway, accelerating the loss of electrons by trans-lycopene and forming the isomerization intermediate lycopene radical, thereby increasing the yield of cis-lycopene isomerization. The study revealed a competitive relationship between electronic effects and mass transfer constraints in the catalytic process: the metal-water interface promotes π-electron rearrangement, which is beneficial for the isomerization reaction; by controlling the presence of water molecules in the reaction environment, the aggregation behavior induced by free water severely restricts the efficiency of reactant transport at the catalytic interface, optimizing the reaction pathway and overcoming the bottleneck of balancing efficiency and selectivity in existing technologies. This provides a new approach for achieving efficient cis-isomerization of lycopene.

[0030] Furthermore, optimizing the catalyst concentration and catalytic time further improved the isomerization efficiency and retention rate of lycopene. Excessively high and long catalyst concentrations and catalytic times may increase the degradation rate of lycopene, while excessively low and short catalyst concentrations and catalytic times cannot achieve trans-lycopene isomerization. Therefore, under the condition of confined water molecules as a mediator to enhance efficiency, multiple conditions are matched with each other, and the content of catalytic medium, catalyst concentration and catalytic time are optimized to achieve synergistic effects and achieve the best lycopene isomerization effect.

[0031] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The method of lycopene isomerization of the present invention uses bimetallic organic framework material as catalyst and confined water as catalytic medium, which is green and environmentally friendly; (2) The method of the present invention can increase the isomerization efficiency of cis-lycopene to a maximum of 82.2%, which is much higher than the thermal isomerization efficiency of 37.6% of the prior art; and the retention rate of lycopene under this process condition can reach a maximum of 90.3%, with higher catalytic stability. Attached Figure Description

[0032] Figure 1 shows the ratio of different types and proportions of metal-doped UIO-66 catalyzing lycopene isomerization.

[0033] Figure 2 is a liquid phase diagram of lycopene isomerization catalyzed by UIO-66;

[0034] Figure 3 shows the HUVEC cell viability assay.

[0035] Figure 4 shows the NIH 3T3 cell viability assay.

[0036] Figure 5 shows the fluorescence pattern of cell viability;

[0037] Figure 6 is a graph showing the hemolysis test of the material.

[0038] Figure 7 is a liquid phase diagram of the catalytic content of trans-lycopene;

[0039] Figure 8 shows the isomerization rate and retention rate of catalytic trans-lycopene solution with varying catalytic media content.

[0040] Figure 9 shows the liquid phase diagram of catalytic trans-lycopene at different material concentrations;

[0041] Figure 10 shows the isomerization rate and retention rate of trans-lycopene catalyzed with different material concentrations;

[0042] Figure 11 shows the liquid phase diagram of trans-lycopene at different catalytic times;

[0043] Figure 12 shows the isomerization rate and retention rate of trans-lycopene catalyzed with different material concentrations;

[0044] Figure 13 shows SEM images of different cis-lycopene contents;

[0045] Figure 14 shows XRD electron micrographs of different cis-lycopene contents;

[0046] Figure 15 is an in-situ temperature-variable X-ray diffraction pattern of water molecules bound to the catalyst. Detailed Implementation

[0047] The technical solution of the present invention will be further described below with reference to the embodiments. The test materials used in the embodiments can all be purchased through conventional means.

[0048] Example 1

[0049] The method for promoting cis-isomerization of lycopene in this invention uses Cu 1 / 4 -UIO-66 material was used as a catalyst to catalyze the cis-isomerization of lycopene.

[0050] Cu 1 / 4 Preparation of UIO-66 material:

[0051] (1) Weigh 0.045 mmol zirconium oxynitrate and 0.015 mmol copper nitrate trihydrate and dissolve them in 7 mL methanol and 1.5 mL acetic acid. Stir at 40 °C until completely dissolved.

[0052] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40 °C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0053] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate the precipitate to a pressure of -0.1MPa, thus obtaining the bimetallic organic framework material Cu of the present invention. 1 / 4-UIO-66.

[0054] The specific method for cis-isomerization of lycopene is as follows: 1 mg of bimetallic organic framework material and 10 mL of lycopene solution (0.1 mmol / L) are added to a round-bottom flask and incubated at 37.5 °C for 1 h. The mixture is then stirred magnetically and heated in a hot reflux water bath. The reaction is carried out in the dark.

[0055] Example 2

[0056] Compared to Example 1, in the method for promoting cis-isomerization of lycopene, the catalyst was changed to iron-doped Fe. 1 / 2 -UIO-66, the molar amount of doping is 50% of the total molar amount of metal ligands.

[0057] Fe 1 / 2 Preparation of UIO-66 material:

[0058] (1) Weigh 0.03 mmol zirconium oxynitrate and 0.03 mmol ferric nitrate nonahydrate and dissolve them in 7 mL methanol and 1.5 mL acetic acid. Stir at 40 °C until completely dissolved.

[0059] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40°C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0060] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate the air until the pressure reaches -0.1MPa, thus obtaining the bimetallic organic framework material Fe of the present invention. 1 / 2 -UIO-66.

[0061] Example 3

[0062] Compared to Example 1, in the method for promoting cis-isomerization of lycopene, the catalyst was changed to zinc ion-doped Zn. 1 / 5 -UIO-66, with a doping molar amount of 20% of the total metal ion molar amount.

[0063] Zn 1 / 5 Preparation of UIO-66 material:

[0064] (1) Weigh 0.048 mmol zirconium oxynitrate and 0.012 mmol zinc nitrate hexahydrate and dissolve them in 7 mL methanol and 1.5 mL acetic acid. Stir at 40 °C until completely dissolved.

[0065] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40°C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0066] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate the precipitate to a pressure of -0.1MPa, thus obtaining the bimetallic organic framework material Zn of the present invention. 1 / 5 -UIO-66.

[0067] Example 4

[0068] Compared to Example 1, in the method for promoting cis-isomerization of lycopene, the catalyst was changed to zinc ion-doped Zn. 1 / 4 -UIO-66, with a doping molar amount of 25% of the total metal ion molar amount.

[0069] Zn 1 / 4 Preparation of UIO-66 material:

[0070] (1) Weigh 0.045 mmol zirconium oxynitrate and 0.015 mmol zinc nitrate hexahydrate and dissolve them in 7 mL methanol and 1.5 mL acetic acid. Stir at 40 °C until completely dissolved.

[0071] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40°C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0072] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate the precipitate to a pressure of -0.1MPa, thus obtaining the bimetallic organic framework material Zn of the present invention. 1 / 4 -UIO-66.

[0073] Example 5

[0074] Compared to Example 1, in the method for promoting cis-isomerization of lycopene, the catalyst was changed to zinc ion-doped Zn. 1 / 2 -UIO-66, with a doping molar amount of 50% of the total metal ion molar amount.

[0075] Zn 1 / 2 Preparation of UIO-66 material:

[0076] (1) Weigh 0.03 mmol zirconium oxynitrate and 0.03 mmol zinc nitrate hexahydrate and dissolve them in 7 mL methanol and 1.5 mL acetic acid. Stir at 40 °C until completely dissolved.

[0077] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40°C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0078] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate the precipitate to a pressure of -0.1MPa, thus obtaining the bimetallic organic framework material Zn of the present invention. 1 / 2 -UIO-66.

[0079] Example 6

[0080] Compared to Example 1, in the method for promoting cis-isomerization of lycopene, the catalyst was changed to copper-doped Cu. 1 / 5 -UIO-66, the molar amount added is 20% of the total molar amount of metal ions.

[0081] Cu 1 / 5 Preparation of UIO-66 material:

[0082] (1) Weigh 0.048 mmol zirconium oxynitrate and 0.012 mmol copper nitrate trihydrate and dissolve them in 7 mL methanol and 1.5 mL acetic acid. Stir at 40 °C until completely dissolved.

[0083] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40°C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0084] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate the precipitate to a pressure of -0.1MPa, thus obtaining the bimetallic organic framework material Cu of the present invention. 1 / 5 -UIO-66.

[0085] Example 7

[0086] Compared to Example 1, in the method for promoting cis-isomerization of lycopene, the catalyst was changed to copper-doped Cu. 1 / 2 -UIO-66, the molar amount added is 50% of the total molar amount of metal ions.

[0087] Cu 1 / 2 Preparation of UIO-66 material:

[0088] (1) Weigh 0.03 mmol zirconium oxynitrate and 0.03 mmol copper nitrate trihydrate and dissolve them in 7 mL methanol and 1.5 mL acetic acid. Stir at 40 °C until completely dissolved.

[0089] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40°C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0090] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate the precipitate to a pressure of -0.1MPa, thus obtaining the bimetallic organic framework material Cu of the present invention. 1 / 2 -UIO-66.

[0091] Example 8

[0092] Compared to Example 1, in the method for promoting cis-isomerization of lycopene, the catalyst was changed to iron-doped Fe. 1 / 5 -UIO-66, with a doping molar amount of 20% of the total metal ion molar amount.

[0093] Fe 1 / 5 Preparation of UIO-66 material:

[0094] (1) Weigh 0.048 mmol zirconium oxynitrate and 0.012 mmol ferric nitrate nonahydrate and dissolve them in 7 mL methanol and 1.5 mL acetic acid. Stir at 40 °C until completely dissolved.

[0095] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40°C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0096] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate the air until the pressure reaches -0.1MPa, thus obtaining the bimetallic organic framework material Fe of the present invention. 1 / 5 -UIO-66.

[0097] Example 9

[0098] Compared to Example 1, in the method for promoting cis-isomerization of lycopene, the catalyst was changed to iron-doped Fe. 1 / 4 -UIO-66, with a doping molar amount of 25% of the total metal ion molar amount.

[0099] Fe 1 / 4 Preparation of UIO-66 material:

[0100] (1) Weigh 0.045 mmol zirconium oxynitrate and 0.015 mmol ferric nitrate nonahydrate and dissolve them in 7 mL methanol and 1.5 mL acetic acid. Stir at 40 °C until completely dissolved.

[0101] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40°C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0102] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate the air until the pressure reaches -0.1MPa, thus obtaining the bimetallic organic framework material Fe of the present invention. 1 / 4 -UIO-66.

[0103] Comparative Example 1

[0104] Compared to Example 1, in the method for promoting cis-isomerization of lycopene, the catalyst was changed to UIO-66 material without metal ion doping:

[0105] Preparation of UIO-66 material:

[0106] (1) Weigh 0.06 mmol of zirconium oxynitrate and dissolve it in 7 mL of methanol and 1.5 mL of acetic acid. Stir at 40 °C until completely dissolved.

[0107] (2) Add 1.429 mL of a methanol solution of tetrafluoroterephthalic acid (10 mg / mL) to the above solution, stir at 40°C for 12 h, and wash three times by centrifugation at 3000 rpm / min for 1 min each time.

[0108] (3) After washing, the precipitate is placed in a vacuum drying oven and dried (50°C, 8h). The vacuum pump is turned on to evacuate and dry to a pressure of -0.1MPa, thus obtaining the metal-organic framework material UIO-66 of the present invention.

[0109] The methods for cis-isomerization of lycopene in Examples 1-9 and the isomerization method in Comparative Example 1 were described. The resulting lycopene mixed solution was filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane filter and then analyzed by high-performance liquid chromatography (HPLC). As shown in Figure 2, the chromatographic peak at retention time 34 min was for 13-cis-lycopene, at 38 min for 9-cis-lycopene, at 42 min for all-trans-lycopene, and at 43 min for 5-cis-lycopene. The total cis isomer content (%), the content of individual isomers (%), and the lycopene retention rate (%) were calculated as follows:

[0110] The isomerization results are shown in Table 1:

[0111] Table 1. Results of cis-isomerization of lycopene

[0112] As shown in Table 1, Cu 1 / 4-The retention rate of UIO-66 was 82.63%, the total isomerization rate was 60.30%, and the 5-cis isomerization rate was 40.20%. Fe 1 / 2 The retention rate of -UIO-66 was 84.47%, the total isomerization rate was 46.95%, and the 5-cis isomerization rate was 24.75%. Analysis combining the retention rate, total isomerization rate, and 5-cis isomerization rate indicates that Cu... 1 / 4 -UIO-66 and Fe 1 / 2 -UIO-66 showed the best effect in the cis isomerization of lycopene. This is because the doping of appropriate amounts of Fe and Cu enhances the electron-accepting ability of UIO-66, resulting in a higher cis isomerization rate of lycopene.

[0113] In the above embodiments, Cu 1 / 4 -UIO-66 and Fe 1 / 2 -Studies on the biocompatibility of UIO-66:

[0114] Preferred methods for Cu production include using human venous endothelial cells (HUVECs) and mouse embryonic fibroblasts (NIH 3T3). 1 / 4 -UIO-66 and Fe 1 / 2 - Cytotoxicity assay of UIO-66. Both cell lines were cultured in DMEM at 37°C in humid air containing 5% CO2.

[0115] The cytotoxicity of HUVECs and NIH 3T3 cells was assessed using the CCK-8 assay. Cells were seeded in 96-well plates and cultured in DMEM containing triple antibodies for 24 h. Subsequently, the original medium was discarded, and Cu was added to the medium. 1 / 4 -UIO-66 and Fe 1 / 2 Fresh UIO-66 medium (0.2, 0.1 mg / mL) was added. After incubation for 24 hours, cells were washed three times with PBS to remove adhering material. Then, fresh medium containing 10% CCK-8 was added. Cells were incubated at 37°C for 0.5 hours. Relative cell viability was determined by measuring absorbance at 450 nm using an enzyme-linked immunosorbent assay (ELISA) labeling.

[0116] Live and dead cells were determined using an AO / PI dual reagent kit. Specifically, the cell culture and material incubation procedures were the same as for CCK-8, but 14-well plates were used for seeding, and the seeding concentration was 1*10⁵. Additionally, considering the concentration of materials used in actual applications, the material incubation concentration was changed (0.5 mg / mL). After incubation, staining agents were added, and cell fluorescence was recorded under an inverted fluorescence microscope (Nikon 80i).

[0117] As shown in Figures 3 and 4, the CCK-8 cell viability assay results indicate that when the material concentration reaches 0.2 mg / mL, the survival rate of HUVECs and NIH 3T3 cells remains above 80%. Furthermore, the cell live-death fluorescence assay also verified that live cells maintained green fluorescence after incubation, while dead cells showed almost no red fluorescence (Figure 5), consistent with the CC-K8 detection results. Simultaneously, the mouse erythrocyte hemolysis assay results (Figure 6) show that 0.2 mg / mL Cu... 1 / 4 -UIO-66 and Fe 1 / 2 -UIO-66 has a blood cell rupture rate far below 5%. In summary, Cu 1 / 4 -UIO-66 and Fe 1 / 2 -UIO-66 has a high level of biocompatibility.

[0118] Example 10

[0119] The present invention provides a highly efficient and stable method for lycopene isomerization, using a Cu-doped MOF-801 transition metal-based nanomaterial as the bimetallic organic framework material. The method involves adding 1% confined water to the catalytic system and specifically includes the following steps:

[0120] (1) Weigh 10 mg of trans-lycopene and dissolve it in 20 mL of acetone solution. Weigh 10 mg of bimetallic organic framework material and add it to the reaction system. The catalyst concentration is 0.5 mg / mL. Further add 200 μL of confined water to the reaction system to form a catalytic system.

[0121] (2) Transfer the above catalytic system to a 37°C water bath, stir magnetically at 600 rpm / min, and catalyze for 1 h.

[0122] (3) After catalysis, the solution was centrifuged at 8000 rpm / min to recover the catalyst precipitate. A cis-lycopene acetone solution was obtained and stored at 4°C protected from light for liquid chromatography analysis.

[0123] The preparation method of the bimetallic organic framework material is as follows: 5 mmol of fumaric acid, 3.75 mmol of zirconium oxychloride octahydrate, and 1.25 mmol of copper nitrate trihydrate are dissolved in a mixed solution of 20 mL DMF and 7 mL of formic acid. The mixture is then thoroughly stirred and homogenized. The mixture is transferred to a high-pressure reactor and placed in an oven (130℃, 6 h). After the reaction is complete, the mixture is cooled to room temperature. The precipitate is then washed four times by centrifugation with DMF and methanol. The precipitate after washing is placed in a vacuum drying oven and dried (50℃, 8 h). The vacuum pump is turned on to dry the precipitate to a pressure of -0.1 MPa, thus obtaining Cu-doped MOF-801 transition metal-based nanomaterials.

[0124] Example 11

[0125] Compared with Example 10, the highly efficient and stable lycopene isomerization method of the present invention, which adds 2% confined water to the catalytic system, specifically includes the following steps:

[0126] (1) Weigh 10 mg of trans-lycopene and dissolve it in 20 mL of acetone solution. Weigh 10 mg of bimetallic organic framework material and add it to the reaction system. The catalyst concentration is 0.5 mg / mL. Further add 400 μL of confined water to the reaction system to form a catalytic system.

[0127] (2) Transfer the above catalytic system to a 37°C water bath, stir magnetically at 600 rpm / min, and catalyze for 1 h.

[0128] (3) After catalysis, the solution was centrifuged at 8000 rpm / min to recover the catalyst precipitate. The cis-lycopene acetone solution was obtained and stored at 4°C protected from light for liquid chromatography analysis.

[0129] Comparative Example 2

[0130] Compared to Example 10, the water molecule content is 0%.

[0131] (1) Weigh 10 mg of trans-lycopene and dissolve it in 20 mL of acetone solution. Weigh 10 mg of bimetallic organic framework material and add it to the reaction system.

[0132] (2) Transfer the above reaction system to a 37°C water bath, stir magnetically at 600 rpm / min, and catalyze for 1 h.

[0133] (3) After catalysis, the solution was centrifuged at 8000 rpm / min to recover the catalyst precipitate. The cis-lycopene acetone solution was obtained and stored at 4°C protected from light for liquid chromatography analysis.

[0134] Comparative Example 3

[0135] Compared to Example 10, the water molecule content is 5%.

[0136] (1) Weigh 10 mg of trans-lycopene and dissolve it in 20 mL of acetone solution. Weigh 10 mg of bimetallic organic framework material and add it to the reaction system. Further add 1000 μL of water to the reaction system to form a catalytic system.

[0137] (2) Transfer the above catalytic system to a 37°C water bath, stir magnetically at 600 rpm / min, and catalyze for 1 h.

[0138] (3) After catalysis, the solution was centrifuged at 8000 rpm / min to recover the catalyst precipitate. The cis-lycopene acetone solution was obtained and stored at 4°C protected from light for liquid chromatography analysis.

[0139] As shown in Figures 7 and 8, when 1% and 2% of confined water molecules were added to the catalytic system, the proportion of cis-lycopene increased from 34.9% (in anhydrous system) to 72.9% and 82.2%, respectively, with retention rates of 93.6% and 90.3%. However, as the water molecule concentration increased to 5%, the lycopene retention rate dropped to only 32%. Therefore, adding 1% and 2% confined water molecules to the catalytic system is more conducive to the isomerization of trans-lycopene, especially with 2% confined water, the isomerization effect is optimal.

[0140] In-situ variable-temperature X-ray diffraction analysis confirmed the morphology of "confined water." As shown in Figure 15, the XRD pattern of Cu-MOF-801 changed significantly after water absorption (e.g., new peaks appeared at 2θ = 13.1° and 17.3°, while characteristic peaks disappeared at 22.1° and 24.5°), indicating that water molecules coordinated with Cu²⁺, leading to local crystal structure reconstruction. This demonstrates that in Cu-MOF-801, water molecules exist in a "confined state" form that specifically binds to metal sites.

[0141] Comparative Example 4

[0142] Compared to Example 10, the concentration of the bimetallic organic framework material was changed to 0 mg / mL.

[0143] (1) Weigh 10 mg of trans-lycopene and dissolve it in 20 mL of acetone solution. Add 200 μL of confined water to the reaction system to form a catalytic system.

[0144] (2) Transfer the above catalytic system to a 37°C water bath, stir magnetically at 600 rpm / min, and catalyze for 1 h.

[0145] (3) After catalysis, the solution was centrifuged at 8000 rpm / min to recover the catalyst precipitate. The cis-lycopene acetone solution was obtained and stored at 4°C protected from light for liquid chromatography analysis.

[0146] Comparative Example 5

[0147] Compared to Example 10, the concentration of the bimetallic organic framework material was changed to 0.1 mg / mL.

[0148] (1) Weigh 10 mg of trans-lycopene and dissolve it in 20 mL of acetone solution. Weigh 2 mg of bimetallic organic framework material and add it to the reaction system. Further add 200 μL of confined water to the reaction system to form a catalytic system.

[0149] (2) Transfer the above catalytic system to a 37°C water bath, stir magnetically at 600 rpm / min, and catalyze for 1 h.

[0150] (3) After catalysis, the solution was centrifuged at 8000 rpm / min to recover the catalyst precipitate. The cis-lycopene acetone solution was obtained and stored at 4°C protected from light for liquid chromatography analysis.

[0151] Comparative Example 6

[0152] Compared to Example 10, the concentration of the bimetallic organic framework material was changed to 1 mg / mL.

[0153] (1) Weigh 10 mg of trans-lycopene and dissolve it in 20 mL of acetone solution. Weigh 20 mg of bimetallic organic framework material and add it to the reaction system. Further add 200 μL of confined water to the reaction system to form a catalytic system.

[0154] (2) Transfer the above catalytic system to a 37°C water bath, stir magnetically at 600 rpm / min, and catalyze for 1 h.

[0155] (3) After catalysis, the solution was centrifuged at 8000 rpm / min to recover the catalyst precipitate. The cis-lycopene acetone solution was obtained and stored at 4°C protected from light for liquid chromatography analysis.

[0156] Comparative Example 7

[0157] Compared to Example 10, the catalytic time was changed to 2 hours.

[0158] (1) Weigh 10 mg of trans-lycopene and dissolve it in 20 mL of acetone solution. Weigh 10 mg of bimetallic organic framework material and add it to the reaction system. Further add 200 μL of confined water to the reaction system to form a catalytic system.

[0159] (2) Transfer the above catalytic system to a 37°C water bath and stir magnetically at 600 rpm / min for 2 hours.

[0160] (3) After catalysis, the solution was centrifuged at 8000 rpm / min to recover the catalyst precipitate. The cis-lycopene acetone solution was obtained and stored at 4°C protected from light for liquid chromatography analysis.

[0161] Comparative Example 8

[0162] Compared to Example 10, the catalytic time was changed to 0.5 h.

[0163] (1) Weigh 10 mg of trans-lycopene and dissolve it in 20 mL of acetone solution. Weigh 10 mg of bimetallic organic framework material and add it to the reaction system. Further add 200 μL of confined water to the reaction system to form a catalytic system.

[0164] (2) Transfer the above catalytic system to a 37°C water bath, stir magnetically at 600 rpm / min, and catalyze for 0.5 h.

[0165] (3) After catalysis, the solution was centrifuged at 8000 rpm / min to recover the catalyst precipitate. The cis-lycopene acetone solution was obtained and stored at 4°C protected from light for liquid chromatography analysis.

[0166] As shown in Figures 9 and 10, the isomerization rate was 37.5% and the retention rate was 96.2% when the catalyst concentration was 0.1 mg / mL, and the isomerization rate was 82.2% and the retention rate was 90.3% when the catalyst concentration was 0.5 mg / mL. However, when the catalyst concentration was increased to 1 mg / mL, the isomerization rate of cis-lycopene was only 77.2%, and the lycopene retention rate decreased to 25.2%. Therefore, the isomerization effect was optimal when the catalyst concentration was 0.5 mg / mL.

[0167] As shown in Figures 11 and 12, the isomerization rate was 22.9% and the retention rate was 96.9% when the catalytic time was 0.5 h; the isomerization rate was 82.2% and the retention rate was 90.3% when the catalytic time was 1 h; when the catalytic time was extended to 2 h, the isomerization rate of cis-lycopene was 63.1%, but the retention rate decreased to 22.2%. Therefore, the isomerization effect was optimal when the catalytic time was 1 h.

[0168] SEM electron microscopy analysis of different cis-lycopene contents:

[0169] (1) Select the standard trans-lycopene, the product lycopene (37.5-Z) in Comparative Example 4, the product lycopene (77.2%-Z) in Comparative Example 5, and the product lycopene (82.2%-Z) in Example 2 from the above experiment and drop the sample solution onto the silicon wafer and dry it at 15°.

[0170] (2) Further, the microstructure of lycopene with different cis contents was observed using a scanning electron microscope.

[0171] As shown in Figure 13, trans-lycopene forms plate-like crystals, while as the proportion of cis-lycopene in the catalytic system gradually increases, lycopene becomes less likely to crystallize and turns into an amorphous form.

[0172] XRD detection of different cis-lycopene contents:

[0173] (1) Select the standard trans-lycopene, the product lycopene (37.5%-Z) in Comparative Example 3, the product lycopene (77.2%-Z) in Comparative Example 7, and the product lycopene (82.2%-Z) in Example 1 from the above experiments and obtain powder by rotary evaporation at 4°.

[0174] (2) Further X-ray diffraction (XRD) was used to analyze the crystal structure of lycopene with different cis contents.

[0175] As shown in Figure 14, trans-lycopene has a crystalline form, while the crystallinity of lycopene gradually decreases as the proportion of cis-lycopene in the catalytic system gradually increases. This is attributed to the fact that when the content of the Z-isomer increases, it generates huge steric hindrance, thereby reducing the potential attractive π-π force, which leads to a decrease in crystallinity.

[0176] Therefore, the efficient and stable lycopene isomerization method of the present invention improves the isomerization efficiency and retention rate of trans-lycopene by controlling the form of water molecules in the catalytic medium, selecting specific catalysts, and adjusting the catalytic concentration and catalytic time of the catalysts, and has great application prospects.

Claims

1. A highly efficient and stable method for cis-isomerization of lycopene, characterized in that, Using bimetallic organic framework materials as catalysts, lycopene was catalyzed to undergo cis-isomerization.

2. The method according to claim 1, characterized in that, The bimetallic organic framework material is a zirconium-based organic framework material doped with a metal material, with an octahedral crystal structure formed by coordination of the organic ligand tetrafluoroterephthalic acid and metal ions. The metal ions are zirconium ions, copper ions, zinc ions, or iron ions. Among the metal ions, copper ions, zinc ions, or iron ions are doped metal ions, and the molar amount of the doped metal ions is 20-50% of the total molar amount of metal ions.

3. The method according to claim 1, characterized in that, The zirconium-based organic framework material includes UIO-66 or MOF-801, and the bimetallic organic framework material is Zn. 1 / 5 -UIO-66、Zn 1 / 4 -UIO-66、Zn 1 / 2 -UIO-66、Cu 1 / 5 -UIO-66、Cu 1 / 4 -UIO-66、Cu 1 / 2 -UIO-66、Fe 1 / 5 -UIO-66、Fe 1 / 4 -UIO-66、Fe 1 / 2 -UIO-66 or Cu-MOF-801.

4. The method according to claim 1, characterized in that, The method for preparing the bimetallic organic framework material includes the following steps: (1) Dissolve zirconium oxynitrate, copper nitrate trihydrate, zinc nitrate hexahydrate, and ferric nitrate nonahydrate in a solution of methanol and formic acid, respectively, and stir to dissolve to obtain a mixed solution. The molar ratio of zirconium oxynitrate to copper nitrate trihydrate, zinc nitrate hexahydrate, and ferric nitrate nonahydrate is 4:1-1:1, and the volume ratio of methanol to formic acid is 5:1-2:

1. (2) Add tetrafluoroterephthalic acid to the mixed solution, stir, and keep the temperature at 30℃~50℃ for 10~14h. (3) The obtained solid material is centrifuged and washed, and then vacuum dried to obtain a bimetallic organic framework material; the washing agent is methanol, the centrifugation speed is 3000 rpm / min, the centrifugation time is 10 min, and the centrifugation temperature is 10℃~20℃; the vacuum drying temperature is 45℃~60℃, the time is 8~10 h, and the drying pressure is -0.09~-0.1 MPa.

5. The method according to claim 1, characterized in that, The method specifically involves taking bimetallic organic framework material and lycopene solution separately, stirring, and heating in a hot reflux water bath while avoiding light; the resulting lycopene mixture solution is obtained by filtration. The ratio of the bimetallic organic framework material to lycopene is 4:1-2:1, the heating temperature is 25-50℃, the heating time is 0.5-2h, magnetic stirring is used, and the reaction is carried out in a hot reflux water bath while avoiding light.

6. The method according to claim 1, characterized in that, A catalytic medium was also added to form a catalytic system for the preparation of lycopene via cis-isomerization.

7. The method according to claim 6, characterized in that, The catalyst medium is confined water, and the volume percentage of the catalyst medium in the catalytic system is 1-2%.

8. The method according to claim 6, characterized in that, The method is specifically as follows: (1) Dissolve trans-lycopene in acetone, add bimetallic organic framework material to the reaction system, and add catalytic medium to the reaction system to form a catalytic system; (2) The above catalytic system was subjected to a water bath and heated with stirring; (3) After catalysis, the solution is centrifuged to recover the catalyst precipitate, thus obtaining cis-lycopene acetone solution, completing the isomerization of lycopene.

9. The method according to claim 8, characterized in that, The bimetallic organic framework material is a Cu-doped MOF-801 transition metal-based nanomaterial.

10. The method according to claim 8, characterized in that, The temperature for water bath heating and stirring is 30-40℃.

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