Catalyst composition, preparation method of zeaxanthin ester and zeaxanthin ester

Abstract

This invention discloses a catalyst composition, a method for preparing zeaxanthin ester, and the zeaxanthin ester itself. The catalyst composition, comprising an alkaline catalyst and a carbonyl iron catalyst, is used to isomerize lutein ester into zeaxanthin ester. Under alkaline conditions, the catalyst composition of this invention allows the carbonyl iron catalyst to complex with the double bond electron cloud of the 4', 5' carbon atom on the terminal benzene ring of the lutein ester molecule, significantly reducing the energy required for the terminal carbon to capture protons. This facilitates the migration of protons from one negative carbon ion site (6' carbon atom) to another site (4' carbon atom), accelerating the transfer of the double bond position. This reduces the activation energy, decreases the amount of alkaline catalyst required, shortens the reaction time, lowers the reaction temperature, and improves the conversion rate and yield of lutein ester.

Description

Technical Field

[0001] This invention relates to the field of zeaxanthin ester technology, and more specifically, to a catalyst composition, a method for preparing zeaxanthin ester, and zeaxanthin ester. Background Technology

[0002] Zeaxanthin ester is an important carotenoid fatty acid ester widely found in plants such as marigolds and pumpkins. Zeaxanthin ester plays a vital role in eye health, possessing strong antioxidant properties. It can quench singlet oxygen and scavenge free radicals, inhibiting oxidative damage to tissues such as the retina and lens caused by various factors. Furthermore, zeaxanthin ester can absorb high-energy blue light from near-ultraviolet light, preventing damage to photoreceptors and retinal cells in the eye. Zeaxanthin ester and lutein ester are isomers, differing mainly in the position of their terminal double bonds. Their structural formulas are as follows:

[0003]

[0004] Currently, the main route to obtain zeaxanthin esters is through the isomerization of lutein esters. However, this isomerization reaction needs to be carried out in a strongly alkaline environment with high temperature. The stronger the alkalinity and the higher the temperature, the more favorable the reaction will be. However, the reaction substrate lutein ester and the reaction product zeaxanthin ester are very unstable in strongly alkaline and high-temperature environments and are easily degraded or even carbonized, resulting in a very low reaction yield. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a catalyst composition, a method for preparing zeaxanthin ester, and zeaxanthin ester. The synergistic effect of the alkaline catalyst and the carbonyl iron catalyst can accelerate the transfer of double bond positions, which is beneficial to reducing the activation energy of the reaction, thereby shortening the reaction time, lowering the reaction temperature, and improving the conversion rate of zeaxanthin ester, thus obtaining a higher content of zeaxanthin ester.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A catalyst composition for isomerizing lutein esters to zeaxanthin esters, comprising a base catalyst and a carbonyl iron catalyst.

[0008] This invention also discloses a method for preparing zeaxanthin esters, comprising the following steps:

[0009] Lutein ester was dissolved and mixed with a solvent, and then an alkaline catalyst and a carbonyl iron catalyst were added to carry out an isomerization reaction to obtain the zeaxanthin ester.

[0010] The present invention also discloses a zeaxanthin ester obtained by the preparation method described above.

[0011] Implementing the embodiments of the present invention will have the following beneficial effects:

[0012] The catalyst composition of this invention involves, under alkaline conditions, a carbonyl iron catalyst complexing with the electron cloud of the double bond on the 4', 5' carbon atom of the terminal benzene ring of the lutein ester molecule, and subsequently forming a large π-bond complex with the exocyclic double bond. The double bond in the large π-bond complex is isomerized into a β-double bond complex due to electron delocalization, followed by the departure of the carbonyl iron, completing the transfer of the double bond from the 4', 5' carbon position to the 5', 6' position, thereby yielding zeaxanthin ester. Specifically, the complexation of the intramolecular double bond of the terminal benzene ring of the lutein ester molecule with carbonyl iron significantly reduces the energy required for the terminal carbon to capture a proton. This facilitates the migration of protons from one negative carbanion site (6' carbon atom) to another site (4' carbon atom), accelerating the transfer of the double bond position, which is beneficial for lowering the activation energy, thus shortening the reaction time, reducing the reaction temperature, and improving the conversion rate and yield of lutein ester. The alkaline catalyst and carbonyl iron catalyst of the present invention work synergistically. The alkaline catalyst maintains the entire reaction process under alkaline conditions, which accelerates the reaction and avoids the hydrolysis of lutein ester and zeaxanthin ester under acidic conditions, thereby reducing the consumption of alkali by ester hydrolysis. The carbonyl iron catalyst enables the reaction to be carried out at a lower temperature and a shorter time, which can effectively protect the thermal degradation of lutein ester and zeaxanthin ester during the reaction process, thereby obtaining a higher content of zeaxanthin ester. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0014] in:

[0015] Figure 1 This is the HPLC chromatogram of Example 1 of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] This invention discloses a catalyst composition for isomerizing lutein esters into zeaxanthin esters, comprising an alkaline catalyst and a carbonyl iron catalyst.

[0018] Specifically, the catalyst composition of the present invention, under alkaline conditions, allows the carbonyl iron catalyst to complex with the double bond electron cloud on the 4' and 5' carbon atoms of the terminal benzene ring of the lutein ester molecule, greatly reducing the energy required for the terminal carbon to capture protons. Protons can more easily migrate from one negative carbon ion site (6' carbon atom) to another site (4' carbon atom), accelerating the transfer of double bond positions. This is beneficial for reducing the activation energy of the reaction, reducing the amount of alkali used, shortening the reaction time, lowering the reaction temperature, and improving the conversion rate and reaction yield of lutein esters. It also avoids the degradation or even carbonization of lutein esters and zeaxanthin esters under strongly alkaline and high-temperature environments.

[0019] Alkaline catalysts are common intermediate compounds that can react with lutein ester molecules through proton acceptance to form reactive carbocation intermediates. In one specific embodiment, the alkaline catalyst includes one or more of potassium tert-butoxide, potassium hydroxide, and sodium hydroxide.

[0020] In one specific embodiment, the carbonyl iron catalyst includes one or both of pentacarbonyl iron and dodecacarbonyl iron.

[0021] This invention also discloses a method for preparing zeaxanthin esters, comprising the following steps:

[0022] 1) Lutein ester was dissolved in a solvent and mixed, then an alkaline catalyst and a carbonyl iron catalyst were added to carry out an isomerization reaction to obtain zeaxanthin ester.

[0023] In one specific embodiment, step 1) specifically includes the following steps:

[0024] 1.1) Lutein esters were mixed with solvents and then subjected to an isomerization reaction at 70℃~100℃ for 1 hour to 3 hours to obtain zeaxanthin esters.

[0025] Specifically, under alkaline conditions, the carbonyl iron catalyst complexes with the double bonds on the 4' and 5' carbon atoms of the terminal benzene ring of the lutein ester molecule, and subsequently forms a large π-bond complex with the exocyclic double bond. The double bond in the large π-bond complex is isomerized to a β-double bond complex due to electron delocalization. Then, the carbonyl iron is removed, completing the transfer of the double bond from the 4' and 5' carbon positions to the 5' and 6' positions, thus yielding zeaxanthin ester. The mechanism of action is as follows:

[0026]

[0027] Therefore, carbonyl iron catalysts and alkaline catalysts enable the reaction to proceed at lower temperatures and shorter times, effectively avoiding slow reaction rates at low temperatures and thermal degradation of lutein esters and zeaxanthin esters under high temperature and strong alkaline conditions.

[0028] In one specific embodiment, the amount of alkaline catalyst added is 0.1% to 1.0% of the mass of lutein ester. Specifically, the alkaline catalyst maintains the entire reaction process under alkaline conditions, accelerating the reaction while preventing lutein ester and zeaxanthin ester from being more easily degraded under acidic conditions.

[0029] In one specific embodiment, the amount of carbonyl iron catalyst added is 1.0% to 2.0% of the mass of lutein ester.

[0030] In one specific embodiment, in order to protect the reaction raw materials lutein ester and the generated zeaxanthin ester from oxidation, the entire reaction process must be carried out in an inert environment.

[0031] In one specific embodiment, the solvent includes one or more of n-propanol, isopropanol, and ethylene glycol.

[0032] In one specific embodiment, the preparation method further includes:

[0033] 2) The zeaxanthin ester was concentrated to remove the solvent, yielding the first intermediate product.

[0034] In one specific embodiment, step 2) specifically includes: adding zeaxanthin ester to a vacuum water pump for reduced pressure concentration to remove solvent, with the concentration temperature being 60°C to 70°C.

[0035] 3) The first intermediate product was washed with water to remove the alkaline catalyst and the carbonyl iron catalyst, and the purified zeaxanthin ester was obtained.

[0036] In one specific embodiment, the water washing temperature is 60°C to 65°C, and the water washing time is 30 minutes to 45 minutes.

[0037] The embodiments of the present invention achieve purification of zeaxanthin esters through concentration and water washing operations. The process is simple, does not require purification processes such as recrystallization, and all operations are carried out at low temperature, which maximizes the stability of zeaxanthin esters. It is highly operable and suitable for industrial-scale production.

[0038] The present invention also discloses a zeaxanthin ester obtained by the preparation method as described in any embodiment of the present invention.

[0039] The following are specific embodiments.

[0040] Example 1

[0041] The preparation method of zeaxanthin ester in this embodiment includes the following steps:

[0042] 6.0 g of lutein ester was weighed and mixed with 30 mL of n-propanol. 0.1% potassium tert-butoxide and 1.0% iron dodecylcarbonyl were added. Under nitrogen protection, the mixture was isomerized at 95 °C for 2 hours. The reaction temperature was then lowered to 60 °C, and the n-propanol was removed by vacuum extraction using a water pump. 9.0 g of deionized water was added, and the mixture was washed at 60 °C for 30 minutes. After cooling to room temperature, the mixture was filtered to recover potassium tert-butoxide and iron dodecylcarbonyl. The product was then vacuum dried at 80 °C to obtain 5.7 g of zeaxanthin ester. Because zeaxanthin ester has very low polarity, the peaks were poor after high-performance liquid chromatography (HPLC). Therefore, the zeaxanthin ester in this example was converted to zeaxanthin before HPLC analysis. HPLC analysis showed that the zeaxanthin content was 76.6%.

[0043] Example 2

[0044] The preparation method of zeaxanthin ester in this embodiment includes the following steps:

[0045] 6.0 g of lutein ester was weighed and mixed with 30 mL of n-propanol. 0.1% potassium tert-butoxide and 1.0% iron dodecylcarbonyl were added. Under nitrogen protection, the mixture was isomerized at 70 °C for 2 hours. The reaction temperature was then lowered to 60 °C, and the n-propanol was removed by vacuum extraction using a water pump. 9.0 g of deionized water was added, and the mixture was washed at 60 °C for 30 minutes. After cooling to room temperature, the mixture was filtered to recover potassium tert-butoxide and iron dodecylcarbonyl. The final product was then vacuum dried at 80 °C to obtain 5.6 g of zeaxanthin ester. High-performance liquid chromatography (HPLC) analysis showed a zeaxanthin content of 70.3%.

[0046] Example 3

[0047] The preparation method of zeaxanthin ester in this embodiment includes the following steps:

[0048] 6.0 g of lutein ester was weighed and mixed with 30 mL of n-propanol. 0.1% potassium tert-butoxide and 1.0% iron dodecylcarbonyl were added. Under nitrogen protection, the mixture was isomerized at 95 °C for 1 hour. The reaction temperature was then lowered to 60 °C, and the n-propanol was removed by vacuum extraction using a water pump. 9.0 g of deionized water was added, and the mixture was washed at 60 °C for 30 minutes. After cooling to room temperature, the mixture was filtered to recover potassium tert-butoxide and iron dodecylcarbonyl. The final product was then vacuum dried at 80 °C to obtain 5.5 g of zeaxanthin ester. High-performance liquid chromatography (HPLC) analysis showed that the zeaxanthin content was 60.3%.

[0049] Example 4

[0050] The preparation method of zeaxanthin ester in this embodiment includes the following steps:

[0051] 6.0 g of lutein ester was weighed and mixed with 30 mL of n-propanol. 0.1% potassium tert-butoxide and 1.0% iron dodecylcarbonyl were added. Under nitrogen protection, the mixture was isomerized at 95 °C for 3 hours. The reaction temperature was then lowered to 60 °C, and the n-propanol was removed by vacuum extraction using a water pump. 9.0 g of deionized water was added, and the mixture was washed at 60 °C for 30 minutes. After cooling to room temperature, the mixture was filtered to recover potassium tert-butoxide and iron dodecylcarbonyl. The final product was then vacuum dried at 80 °C to obtain 5.6 g of zeaxanthin ester. High-performance liquid chromatography (HPLC) analysis showed that the zeaxanthin content was 77.1%.

[0052] Example 5

[0053] The preparation method of zeaxanthin ester in this embodiment includes the following steps:

[0054] 6.0 g of lutein ester was weighed and mixed with 30 mL of n-propanol. 1.0% potassium tert-butoxide and 1.0% ferric dodecylcarbonyl were added. Under nitrogen protection, the mixture was isomerized at 95 °C for 1 hour. The reaction temperature was then lowered to 60 °C, and the n-propanol was removed by vacuum extraction using a water pump. 9.0 g of deionized water was added, and the mixture was washed at 60 °C for 30 minutes. After cooling to room temperature, the mixture was filtered to recover potassium tert-butoxide and ferric dodecylcarbonyl. The final product was then vacuum dried at 80 °C to obtain 5.6 g of zeaxanthin ester. High-performance liquid chromatography (HPLC) analysis showed that the zeaxanthin content was 77.9%.

[0055] Example 6

[0056] The preparation method of zeaxanthin ester in this embodiment includes the following steps:

[0057] 6.0 g of lutein ester was weighed and mixed with 30 mL of isopropanol. 0.1% potassium hydroxide and 1.0% ferric pentacarbonyl were added. Under nitrogen protection, the mixture was isomerized at 95 °C for 1 hour. The reaction temperature was then lowered to 60 °C, and isopropanol was removed by vacuum extraction using a water pump. 9.0 g of deionized water was added, and the mixture was washed at 60 °C for 30 minutes. After cooling to room temperature, the mixture was filtered to recover potassium hydroxide and ferric pentacarbonyl. The final product was then vacuum dried at 80 °C to obtain 5.7 g of zeaxanthin ester. High-performance liquid chromatography (HPLC) analysis showed that the zeaxanthin content was 60.6%.

[0058] Example 7

[0059] The preparation method of zeaxanthin ester in this embodiment includes the following steps:

[0060] 6.0 g of lutein ester was weighed and mixed with 30 mL of isopropanol. 0.5% sodium hydroxide and 1.05% ferric pentacarbonyl were added. Under nitrogen protection, the mixture was isomerized at 95 °C for 3 hours. The reaction temperature was then lowered to 60 °C. Isopropanol was removed by vacuum extraction at 60 °C using a vacuum water pump. 9.0 g of deionized water was added, and the mixture was washed at 60 °C for 30 minutes. After cooling to room temperature, the mixture was filtered to recover sodium hydroxide and ferric pentacarbonyl. The final product was then vacuum dried at 80 °C to obtain 5.5 g of zeaxanthin ester. High-performance liquid chromatography (HPLC) analysis showed that the zeaxanthin content was 61.3%.

[0061] Example 8

[0062] The only difference between this embodiment and Example 1 is that the isomerization reaction temperature was 120°C, while all other experimental conditions remained the same, yielding 4.1 g of zeaxanthin ester. High-performance liquid chromatography analysis showed that the zeaxanthin content was 69.3%.

[0063] Example 9

[0064] The only difference between this example and Example 1 is that the reaction time was 0.5 hours, while all other experimental conditions remained the same, yielding 5.6 g of zeaxanthin ester. High-performance liquid chromatography (HPLC) analysis showed that the zeaxanthin content was 20.4%.

[0065] Example 10

[0066] The only difference between this example and Example 1 is that the reaction time was 7 hours, while all other experimental conditions remained the same, yielding 4.9 g of zeaxanthin ester. High-performance liquid chromatography analysis showed that the zeaxanthin content was 75.1%.

[0067] Example 11

[0068] The only difference between this example and Example 1 is that the amount of potassium tert-butoxide added is 0.05%, while all other experimental conditions are the same, yielding 5.5 g of zeaxanthin ester. High-performance liquid chromatography analysis showed that the zeaxanthin content was 50.3%.

[0069] Example 12

[0070] The only difference between this example and Example 1 is that the amount of potassium tert-butoxide added is 5.0%, while all other experimental conditions are the same, yielding 4.9 g of zeaxanthin ester. High-performance liquid chromatography analysis showed that the zeaxanthin content was 70.5%.

[0071] Comparative Example 1

[0072] The only difference between this comparative example and Example 1 is that it does not contain dodecyl iron.

[0073] The preparation method of the comparative example of zeaxanthin ester includes the following steps:

[0074] Lutein ester was obtained according to the method in Example 1. 6.0 g of lutein ester was weighed and mixed with 30 mL of n-propanol. 1.1% potassium tert-butoxide was added, and the mixture was isomerized at 95°C for 2 hours under nitrogen protection. The reaction temperature was then lowered to 60°C, and the n-propanol was removed by vacuum extraction at 60°C using a vacuum water pump. 9.0 g of deionized water was added, and the mixture was washed at 60°C for 30 minutes. After cooling to room temperature, the mixture was filtered to recover potassium tert-butoxide and iron dodecylcarbonyl. The final product was then vacuum dried at 80°C to obtain 5.5 g of zeaxanthin ester. High-performance liquid chromatography (HPLC) analysis showed that the zeaxanthin content was 15.2%.

[0075] Comparative Example 2

[0076] The only difference between this comparative example and Example 1 is that it does not contain potassium tert-butoxide.

[0077] The preparation method of the comparative example of zeaxanthin ester includes the following steps:

[0078] Lutein ester was obtained according to the method in Example 1. 6.0 g of lutein ester was weighed and mixed with 30 mL of n-propanol. 1.1% iron dodecylcarbonyl was added, and the mixture was isomerized at 95°C for 2 hours under nitrogen protection. The reaction temperature was then lowered to 60°C, and the n-propanol was removed by vacuum extraction at 60°C using a vacuum water pump. 9.0 g of deionized water was added, and the mixture was washed at 60°C for 30 minutes. After cooling to room temperature, the mixture was filtered to recover potassium tert-butoxide and iron dodecylcarbonyl. The final product was then vacuum dried at 80°C to obtain 5.2 g of zeaxanthin ester. High-performance liquid chromatography (HPLC) analysis showed that the zeaxanthin content was 1.1%.

[0079] Test case

[0080] 1. The zeaxanthin ester obtained in Example 1 was characterized by liquid chromatography, and the results are as follows: Figure 1 As shown, Figure 1 The image shows the hourly HPLC chromatogram of Example 1, with the zeaxanthin peak at 9.655 minutes.

[0081] 2. The effect of carbonyl iron catalyst on the yield of zeaxanthin ester was investigated. The yields of zeaxanthin ester obtained in Example 1 and Comparative Examples 1-2 were compared. The experimental results show that the yield of zeaxanthin ester obtained in Comparative Examples 1-2 was lower than that in Example 1. This indicates that under the same reaction conditions, the addition of carbonyl iron catalyst and alkaline catalyst helps to shorten the reaction time, reduce the reaction temperature, and improve the conversion rate of zeaxanthin ester, thus obtaining a high yield of zeaxanthin ester.

[0082] 3. The effect of reaction temperature on the yield of zeaxanthin ester was investigated. The yields of zeaxanthin ester obtained in Examples 1-2 and Example 8 were compared. The results showed that increasing the reaction temperature was beneficial to the conversion of lutein ester into zeaxanthin ester. However, when the reaction temperature reached above 120°C, lutein ester and zeaxanthin ester were oxidized and destroyed, thus reducing the yield of zeaxanthin ester.

[0083] 4. The effect of different reaction times on the yield of zeaxanthin esters was investigated. The yields of zeaxanthin esters obtained in Examples 1, 3-4 and 9-10 were compared. The results showed that increasing the reaction time was beneficial to the conversion of lutein esters into zeaxanthin esters. However, when the reaction time was increased to more than 7 hours, the conversion rate gradually decreased, and some lutein esters and zeaxanthin esters were oxidized and destroyed.

[0084] 5. The effect of different alkali concentrations on zeaxanthin esters was investigated. The yields of zeaxanthin esters obtained in Examples 1, 5, and 11-12 were compared. The results showed that increasing the alkali concentration was beneficial for the isomerization of lutein esters into free zeaxanthin esters. However, when the alkali concentration increased to more than 5.0%, it destroyed the double bonds of lutein esters and the generated zeaxanthin esters, accelerated the decomposition of lutein esters and zeaxanthin esters, and reduced the conversion rate of the reaction.

[0085] By comparing the data from each embodiment and comparative example, it can be seen that the present invention uses lutein ester as raw material, and through the synergistic effect of alkaline catalyst and carbonyl iron catalyst, and by controlling the reaction temperature and reaction time, a high yield of zeaxanthin ester can be obtained.

[0086] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A process for the preparation of a zeaxanthin ester, characterized in that, The method comprises the following steps: After the lutein ester is dissolved and mixed with a solvent, an alkali catalyst and a carbonyl iron catalyst are added, and an isomerization reaction is carried out at a temperature of 70-100 DEG C for 1-3 hours to obtain the zeaxanthin ester; The alkali catalyst is added in an amount of 0.1-1.0% of the mass of the lutein ester, and the carbonyl iron catalyst is added in an amount of 1.0-2.0% of the mass of the lutein ester.

2. The production method according to claim 1, characterized by, The carbonyl iron catalyst comprises one or both of iron pentacarbonyl and iron dodecacarbonyl.

3. The preparation method according to claim 1, characterized in that, The alkali catalyst comprises one or more of potassium tert-butoxide, potassium hydroxide and sodium hydroxide.

4. The production method according to claim 1, characterized by, The method further comprises: The zeaxanthin ester is concentrated to remove the solvent, and a first intermediate product is obtained; The first intermediate product is washed with water to remove the alkali catalyst and the carbonyl iron catalyst, and a purified zeaxanthin ester is obtained.

5. The preparation method according to claim 1, characterized in that, The solvent comprises one or more of n-propanol, isopropanol and ethylene glycol.

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