Long-chain unsaturated fatty acid raffinose monoester as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of food, organic synthesis, saccharides and derivatives thereof, and particularly relates to long-chain unsaturated fatty acid raffinose monoester as well as a preparation method and application thereof. The structural formula of the long-chain unsaturated fatty acid raffinose monoester is shown in the specification, wherein R is C18-C20 alkyl. According to the invention, easily oxidized unsaturated fatty acid is combined on raffinose, so that the sugar monoester surfactant which is easy to digest, good in oxidation stability, excellent in thermal stability and strong in hydrophilicity is obtained. The method has an application prospect in the fields of functional foods and medicines. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the technical field of food, organic synthesis, sugars and their derivatives, and particularly relates to a long-chain unsaturated fatty acid raffinose monoester and a preparation method and application thereof. Background Art

[0002] Very-long-chain polyunsaturated fatty acids (VLC-PUFAs) are essential fatty acids for the human body and possess multiple physiological activities that maintain homeostasis in the body. For example, ω-3 PUFAs have been shown to regulate immunity, maintain microbial diversity, promote brain and nerve development, and maintain vascular health. However, the strong hydrophobicity of their very long carbon chain structures results in a low digestion and absorption rate in the human body. Furthermore, the presence of multiple double bonds (C=C) in the very long carbon chains makes PUFAs highly susceptible to environmental factors (such as oxygen, light, and temperature), leading to varying degrees of oxidation, which reduces their nutritional properties and even harms the human body. Therefore, inhibiting the oxidation of LC-PUFAs and enhancing their hydrophilic dispersibility have been research focuses in recent years. Previous studies have primarily focused on improving the oxidative stability of LC-PUFAs, typically by adding natural or synthetic antioxidants or using specific packaging materials to delay oxidation and maintain their physiological activity. However, the low bioavailability of LC-PUFAs remains a challenge.

[0003] These studies include traditional approaches such as changing packaging materials (vacuum packaging, modified atmosphere packaging, etc.), adding synthetic antioxidants such as butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), and extracting natural antioxidants from plants for use in emulsions (such as tea polyphenols and epigallocatechin gallate). However, the limitations of packaging materials and the harmful effects of synthetic antioxidants have limited their development. Plant-derived proteins have garnered significant attention in recent years, utilizing metal chelators from legume and oilseed proteins to inhibit oxidation in protein emulsions. Because some plant proteins are poorly soluble in water, emulsions lack stability and are more complex to manufacture. Furthermore, emulsion research often fails to determine the detailed composition of these components (particularly non-protein components), limiting their application. Another approach is bio-based particles (often referred to as pickling emulsions). These particles, such as silica and microcrystalline cellulose, form a physical barrier at the emulsion interface to inhibit lipid oxidation. However, the active substances added in this approach, such as silica and microcrystalline cellulose, are indigestible to the human body and exhibit limited antioxidant properties. Therefore, it is of great significance to develop a healthy, easily digestible and widely used substance to inhibit lipid oxidation. Summary of the Invention

[0004] To address the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to provide a long-chain unsaturated fatty acid raffinose monoester. This sugar monoester is formed by combining long-chain polyunsaturated fatty acids (oleic acid OA, linolenic acid ALA, and eicosapentaenoic acid EPA) with raffinose and has an amphiphilic structure. This sugar monoester can be used as a surfactant to prepare a stable oil-in-water (O / W) emulsion. As an emulsifier, it can promote the human body's digestion of lipids in the emulsion. After being hydrolyzed by lipase, this sugar monoester can improve the absorption of unsaturated fatty acids. In addition, this sugar monoester has the advantages of being easily digestible, having good oxidative stability, and being highly hydrophilic.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned long-chain unsaturated fatty acid raffinose monoester. The present invention adopts a chemical method to synthesize sugar monoesters, and the synthesized sugar monoesters can be effectively used in functional foods and medicines.

[0006] Another object of the present invention is to provide an application of the above-mentioned long-chain unsaturated fatty acid raffinose monoester.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] The present invention provides a long-chain unsaturated fatty acid raffinose monoester, the structural formula of which is shown below:

[0009]

[0010] Wherein, R is a C18-C20 alkyl group.

[0011] Preferably, the present invention provides a long-chain unsaturated fatty acid raffinose monoester, the structural formula of which is shown in formula (1), (2) or (3):

[0012]

[0013]

[0014] A method for preparing long-chain unsaturated fatty acid raffinose monoester comprises the following steps:

[0015] Raffinose and unsaturated fatty acids are placed in a reaction vessel, dissolved in a solvent, and then a catalyst is added. The reaction is heated under inert gas and stirring conditions to allow the hydrophobic unsaturated fatty acids to bind to the hydrophilic raffinose. After separation and purification, amphiphilic long-chain unsaturated fatty acid raffinose monoester (light yellow solid) is obtained.

[0016] Preferably, the molar ratio of raffinose to unsaturated fatty acids is 1:1-3.

[0017] Preferably, the mass ratio of the catalyst to raffinose is 1:1.

[0018] Preferably, the solvent is a tert-butanol / pyridine mixed solution.

[0019] More preferably, in the tert-butanol / pyridine mixed solution, the volume ratio of tert-butanol:pyridine is 9:5-15, and the most preferred ratio is 9:11.

[0020] Preferably, the catalyst is O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU).

[0021] Preferably, the unsaturated fatty acid is a fatty acid containing a C18 to C20 carbon chain.

[0022] More preferably, the fatty acid with a carbon chain of C18 to C20 is OA (oleic acid), ALA (linolenic acid) or EPA (eicosapentaenoic acid).

[0023] Preferably, the heating reaction temperature is 45-65°C (more preferably 55°C) and the time is 10-30h (more preferably 24h).

[0024] Preferably, the stirring speed is 400-1000 rpm (more preferably 650 rpm).

[0025] Preferably, the separation and purification method is column chromatography separation.

[0026] Preferably, the reagents used for separation and purification are methanol and dichloromethane.

[0027] More preferably, the ratio of reagents used for separation and purification is methanol: dichloromethane (volume ratio) = 1: 0.05-0.4.

[0028] The present invention also proposes the use of the long-chain unsaturated fatty acid raffinose monoester as a surfactant, for example, in the preparation of an emulsion.

[0029] Preferably, the emulsion can be used in the fields of food, medicine and the like.

[0030] Principle of the present invention:

[0031] Under the action of the catalyst, the methylene proton at C-6 in the unsaturated fatty acid raffinose monoester interacts with the carbonyl carbon of the ester portion, thereby establishing the esterification site at C-6 of the galactose residue in raffinose, thereby producing the long-chain unsaturated fatty acid raffinose monoester. The details are as follows:

[0032]

[0033] The present invention has the following advantages and effects compared to the prior art:

[0034] (1) The present invention adopts the chemical synthesis method commonly used in the surfactant market, the preparation method is simple, and the obtained product has high purity, which is ≥95%.

[0035] (2) The long-chain unsaturated fatty acid raffinose monoester synthesized by the present invention has good water solubility and a high hydrophilic-lipophilic balance value, and can be used as a surfactant to prepare an oil-in-water (O / W) emulsion with strong stability.

[0036] (3) The emulsion prepared by using the long-chain unsaturated fatty acid raffinose monoester synthesized in the present invention as a surfactant has excellent thermal stability. After the emulsion is subjected to high-temperature treatment at 50°C and 90°C, the particle size of the emulsion remains basically unchanged, and the emulsion has excellent stability and can be used for commercial production of dairy products.

[0037] (4) The emulsion prepared using the long-chain unsaturated fatty acid raffinose monoester synthesized in the present invention as a surfactant has excellent storage stability. After 16 days of storage, its particle size has basically not changed, which fully meets the market requirements for the shelf life of the emulsion.

[0038] (5) The long-chain unsaturated fatty acid raffinose monoester synthesized by the present invention can be well digested and absorbed by the human body.

[0039] (6) The long-chain unsaturated fatty acid raffinose monoester synthesized by the present invention has excellent oxidative stability and can effectively inhibit the oxidation of the unsaturated fatty acids in the side chains of the sugar monoester surfactant, thereby improving the stability and bioavailability of the unsaturated fatty acids. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the H NMR spectrum of the long-chain unsaturated fatty acid raffinose monoester prepared in Example 1;

[0041] Figure 2 This is the C NMR spectrum of the long-chain unsaturated fatty acid raffinose monoester prepared in Example 1;

[0042] Figure 3 This is the H NMR spectrum of the long-chain unsaturated fatty acid raffinose monoester prepared in Example 2;

[0043] Figure 4 This is the C NMR spectrum of the long-chain unsaturated fatty acid raffinose monoester prepared in Example 2;

[0044] Figure 5 This is the H NMR spectrum of the long-chain unsaturated fatty acid raffinose monoester prepared in Example 3;

[0045] Figure 6 This is the C NMR spectrum of the long-chain unsaturated fatty acid raffinose monoester prepared in Example 3;

[0046] Figure 7 Graph showing the thermal stability and storage stability test results of the emulsions prepared from the long-chain unsaturated fatty acid raffinose monoesters prepared in Examples 1-3 of the present invention;

[0047] Figure 8 This is a test result diagram of the human gastrointestinal digestion of the emulsion prepared from the long-chain unsaturated fatty acid raffinose monoester prepared in Examples 1-3 of the present invention;

[0048] Figure 9 1 is a graph showing the test results of the antioxidant properties of the long-chain unsaturated fatty acid raffinose monoester prepared in Examples 1-3 of the present invention;

[0049] In the figures, RE, RA, and RO represent the emulsions prepared from the long-chain unsaturated fatty acid raffinose monoesters prepared in Examples 1, 2, and 3, respectively; S-1570 and S-1670 represent the emulsions prepared from commercial sucrose esters. DETAILED DESCRIPTION

[0050] The present invention will be described in further detail below with reference to the examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. The raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically noted, conventional techniques can be used.

[0051] Example 1: Preparation of Raffinose-EPA (RE) Monoester

[0052] Weigh 1g of raffinose (analytical grade) into a flask, add 1g of EPA dropwise, and add 1g of molecular sieves to remove the water produced during the reaction. Add 9mL of tert-butyl alcohol and 11mL of pyridine as solvents, and 1g of O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate as a catalyst. A magnetic stirrer was set at 55°C and 650rpm for 24 hours, under nitrogen protection.

[0053] The reaction was stopped, a layer of diatomaceous earth was placed in a Buchner funnel, the reaction solution was poured in, the molecular sieves in the reaction solution were filtered out by vacuum filtration, and 80% of the tert-butyl alcohol and pyridine solvents in the reaction solution were removed by vacuum concentration.

[0054] The above solution was separated and purified by column chromatography. Methanol / dichloromethane was used for elution. The specific elution steps and volume ratios were as follows (500 mL as an example):

[0055] (1) Dichloromethane:methanol = 470:30;

[0056] (2) dichloromethane:methanol = 440:60;

[0057] (3) dichloromethane:methanol = 410:90;

[0058] (4) Dichloromethane:methanol = 390:110; (target product begins to appear)

[0059] (5) dichloromethane:methanol = 375:125;

[0060] (6) Dichloromethane:methanol = 365:135; (target product stops appearing)

[0061] The target product solution was collected and concentrated under reduced pressure using a rotary evaporator to remove the eluting solution, ultimately yielding a solid powder product. 20 mg was dissolved in deuterated methanol and loaded into a C-1H NMR tube for analysis. The product obtained by this method had a purity of ≥95%.

[0062] Example 2: Preparation of Raffinose-ALA (RA) Monoester

[0063] Weigh 1g of raffinose (analytical grade) into a flask, add 1g of ALA dropwise, and add 1g of molecular sieves to remove the water produced during the reaction. Add 9mL of tert-butyl alcohol and 11mL of pyridine as solvents, and 1g of O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate as a catalyst. A magnetic stirrer is set at 55°C and 650rpm for 24 hours, under a nitrogen atmosphere.

[0064] The reaction was stopped, a layer of diatomaceous earth was placed in a Buchner funnel, the reaction solution was poured in, the molecular sieves in the reaction solution were filtered out by vacuum filtration, and 80% of the tert-butyl alcohol and pyridine solvents in the reaction solution were removed by vacuum concentration.

[0065] The above solution was separated and purified by column chromatography. Methanol / dichloromethane was used for elution. The specific elution steps and volume ratios were as follows (500 mL as an example):

[0066] (1) dichloromethane:methanol = 475:25;

[0067] (2) dichloromethane:methanol = 450:50;

[0068] (3) dichloromethane:methanol = 425:75;

[0069] (4) Dichloromethane: methanol = 400:100; (target product begins to appear)

[0070] (5) dichloromethane:methanol = 385:115;

[0071] (6) Dichloromethane:methanol = 370:130; (the target product stops appearing)

[0072] The target product solution was collected and concentrated under reduced pressure using a rotary evaporator to remove the eluting solution, ultimately yielding a solid powder product. 20 mg was dissolved in deuterated methanol and loaded into a C-1H NMR tube for analysis. The product obtained by this method had a purity of ≥95%.

[0073] Example 3: Preparation of Raffinose-OA (RO) Monoester

[0074] Weigh 1g of raffinose (analytical grade) into a flask, add 1g of OA dropwise, and add 1g of molecular sieves to remove the water produced during the reaction. Add 9mL of tert-butyl alcohol and 11mL of pyridine as solvents, and 1g of O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate as a catalyst. A magnetic stirrer is set at 55°C and 650rpm for 24 hours, under nitrogen protection.

[0075] The reaction was stopped, a layer of diatomaceous earth was placed in a Buchner funnel, the reaction solution was poured in, the molecular sieves in the reaction solution were filtered out by vacuum filtration, and 80% of the tert-butyl alcohol and pyridine solvents in the reaction solution were removed by vacuum concentration.

[0076] The above solution was separated and purified by column chromatography. Methanol / dichloromethane was used for elution. The specific elution steps and volume ratios were as follows (500 mL as an example):

[0077] (1) dichloromethane:methanol = 475:25;

[0078] (2) dichloromethane:methanol = 450:50;

[0079] (3) dichloromethane:methanol = 425:75;

[0080] (4) Dichloromethane: methanol = 400:100; (target product begins to appear)

[0081] (5) dichloromethane:methanol = 385:115;

[0082] (6) Dichloromethane:methanol = 370:130; (the target product stops appearing)

[0083] The target product solution was collected and concentrated under reduced pressure using a rotary evaporator to remove the eluting solution, ultimately yielding a solid powder product. 20 mg was dissolved in deuterated methanol and loaded into a C-1H NMR tube for analysis. The product obtained by this method had a purity of ≥95%.

[0084] Test example

[0085] This test example tests the various properties of the long-chain unsaturated fatty acid raffinose monoester prepared in Examples 1-3. The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum of the long-chain unsaturated fatty acid raffinose monoester prepared in Examples 1-3 are as follows: Figure 1-6 shown.

[0086] (1) The interface properties of long-chain unsaturated fatty acid raffinose monoester are shown in Table 1:

[0087] Table 1

[0088]

[0089] The hydrophile-lipophile balance (HLB) values in the table are determined using the water number method.

[0090] The critical micelle concentration (CMC) was measured using an automatic interfacial tensiometer.

[0091] γCMC is the interfacial tension corresponding to the critical micelle concentration.

[0092] In Table 1, RE, RA, and RO represent the long-chain unsaturated fatty acid raffinose monoesters prepared in Examples 1, 2, and 3, respectively; S-1570 and S-1670 represent commercial sucrose esters. As shown in Table 1, the HLB values of the three long-chain unsaturated fatty acid raffinose monoester samples prepared in Examples 1-3 are all greater than 15, making them suitable for preparation into oil-in-water emulsions. The critical micelle concentrations of the three long-chain unsaturated fatty acid raffinose monoesters prepared in Examples 1-3 are significantly lower than those of the commercial controls S-1570 and S-1670, indicating that the sugar monoester samples prepared in this invention have a stronger ability to reduce interfacial tension than the commercial controls.

[0093] (2) Thermal stability and storage stability

[0094] The prepared samples were each prepared into emulsions as follows: 80 mL of a 0.3% w / w aqueous solution of the three long-chain unsaturated fatty acid raffinose monoesters prepared in Examples 1-3 were placed in 100 mL centrifuge tubes, followed by the addition of 4 g of linseed oil. The mixture was first mixed using a shear disperser (15,000 rpm) for 3 minutes, followed by five cycles using a high-pressure homogenizer (1,000 bar) to obtain a final nanoemulsion sample (5% by weight of linseed oil in the emulsion). The emulsion sample was then placed in a 4°C refrigerator for 24 hours for stabilization, and then tested and analyzed. Deionized water was used.

[0095] 5 mL of the emulsion was placed in a 10 mL glass bottle and then heated in a water bath at 50°C and 90°C for 30 minutes respectively to simulate the sterilization and antibacterial process in dairy product production. The treated emulsion was stored in a 4°C refrigerator for 24 hours and then analyzed. The droplet size and particle size distribution were recorded at 1, 4, 8, 12, and 16 days. The results are as follows Figure 7The results show that the particle size of the emulsions after heat treatment at 50°C and 90°C did not change significantly compared to the untreated emulsion, indicating that the emulsions prepared with the sugar monoesters described in the present invention have good thermal stability. In addition, the particle size change of all emulsion samples remained within ±30nm during the 15-day monitoring period, indicating excellent shelf life stability.

[0096] (3) Testing of human gastrointestinal digestion

[0097] The digestibility of the emulsion in the human body was evaluated by calculating the free fatty acids (FFA) released from the emulsion in the small intestine under simulated gastrointestinal working conditions. The following is a brief introduction to the operating procedures.

[0098] Prior to the experiment, the oil content of the emulsion (prepared using the same process as described for the thermal and storage stability experiments) was diluted to 2 wt % using phosphate buffered saline. During the oral phase, 20 mL of the diluted emulsion was mixed with 20 mL of artificial saliva solution and the pH was adjusted to 6.8. The mixture was then placed in an incubator shaker (37°C, 100 rpm) for 10 min before the oral phase was completed. During the gastric digestion phase, 25 mL of the oral digestion sample was mixed with 25 mL of simulated gastric fluid working solution (containing 0.08 g of pepsin), the pH was adjusted to 2.5, and the mixture was shaken in an incubator shaker for 2 h before the gastric digestion phase was completed. During the small intestinal phase, 1.5 mL of simulated intestinal fluid was added to 30 mL of the gastric digestion sample, followed by 3.5 mL of bile salt solution to adjust the pH to 6.995-6.999 (slightly less than 7). The pH of the system was monitored and controlled using an automated titrator (Metrohm USA, Inc.) and titrated with 0.1 mM NaOH. After the small intestinal digestion program starts, 2.5 mL of lipase solution is added according to the system prompts. Small intestinal digestion should be carried out at 37 ° C for 2 hours. After the small intestinal digestion is completed, the release of free fatty acids is calculated according to the titration curve. The release rate of free fatty acids (FFA) in the gastric and intestinal stages of the emulsion samples prepared with the three long-chain unsaturated fatty acid raffinose monoesters prepared in Examples 1-3 was determined. Throughout the experiment, 0.1 mM NaOH solution was used for titration, and the reaction system was maintained at a gastric phase pH of 2.5 and an intestinal phase pH of 7.0, and an automatic titration device was used for monitoring. The release of free fatty acids was calculated using the following formula:

[0099]

[0100] In the formula, V NaOH and C NaOH are the volume and concentration of NaOH added, M lipid and W lipid are the molar mass and weight of digestible lipids in the simulated small intestine, respectively.

[0101] The test results are as follows Figure 8 As shown, the results show that the emulsions prepared with the three long-chain unsaturated fatty acid raffinose monoesters prepared in Examples 1-3 can be well enzymatically hydrolyzed during the digestion process, thereby releasing the side chain unsaturated fatty acids from the sugar ester structure and then being absorbed and utilized by the human body, indicating that the long-chain unsaturated fatty acid raffinose monoesters prepared by the present invention can be well digested and absorbed by the human body.

[0102] (4) Oxidation stability test

[0103] The three long-chain unsaturated fatty acid raffinose monoesters prepared in Examples 1-3 were respectively prepared into emulsions according to the following steps:

[0104] In the lipid oxidation experiment, corn oil was used to prepare an oil-in-water solution. 50 mL of a 0.3% w / w sugar monoester aqueous solution was prepared, 5% by mass corn oil was added, and the mixture was then dispersed at 15,000 rpm for 5 minutes. Deionized water was used.

[0105] The prepared emulsion was placed in a dark box and incubated at 55°C for 15 days. The primary oxidation products and secondary oxidation products on days 0, 3, 6, 9, 12, and 15 were recorded. The detailed steps are as follows:

[0106] Primary oxidation products - peroxide value (PV)

[0107] The emulsion was incubated in the dark at 55°C for 15 days, with testing every two days. First, lipids were extracted from the emulsion. 0.3 mL of the emulsion was mixed with 1.5 mL of isooctane / 2-propanol (3:1 v / v) and vortexed three times for 10 seconds each time, followed by centrifugation at 3500 rpm for 2 minutes. 0.2 mL of the isooctane / 2-propanol extract (the top layer) was then mixed with 2.8 mL of methanol / 1-butanol (2:1 v / v), followed by the addition of 30 μL of a 1:1 v / v 3.94 M ammonium thiocyanate / ferrous iron solution (equal parts 0.132 M BaCl₂ and 0.144 M FeSO₄). After incubation at room temperature with vortexing for 20 minutes, absorbance was measured at 510 nm using a UV-visible spectrophotometer. A calibration curve was prepared using cumene hydroperoxide to calculate the hydroperoxide concentration. Deionized water was used as a blank, and each sample was prepared in triplicate.

[0108] Secondary oxidation product - thiobarbituric acid reaction product (Tbars)

[0109] Place 2 mL of TBA reagent in a centrifuge tube, add 1 mL of sample, and vortex twice for 10 seconds each time to mix thoroughly. Place the mixed sample in a water bath (90°C) for 15 minutes, then place in a cold water bath for 10 minutes, and finally centrifuge at 5000 rpm for 15 minutes. Take 2.5 mL of the supernatant and place it in a quartz cuvette. Measure the absorbance at 532 nm, taking care to avoid bubbles in the cuvette when adding the sample. Use 1,1,3,3-tetraethoxypropane (TEP) to prepare a standard curve and calculate the Tbars concentration. Use deionized water as a blank control, and perform triplicates for each sample.

[0110] The above TBA reagent was prepared as follows (250 mL):

[0111] 1) Prepare 250 gr of TCA-TBA-HCl solution:

[0112]

[0113] TCA = trichloroacetic acid, TBA = thiobarbituric acid

[0114] 2) Dissolve TBA thoroughly under stirring and slight heating, then cool to room temperature;

[0115] 3) Prepare 2% BHT ethanol solution:

[0116]

[0117] BHT is butylated hydroxytoluene

[0118] 4) Stir and mix the two solutions, then place in the refrigerator;

[0119] 5) The solution should become clear with white crystals precipitating.

[0120] Each emulsion sample was tested three times to obtain the average value. Figure 9 The test results show that the concentrations of primary and secondary oxidation products in the emulsions prepared with the three long-chain unsaturated fatty acid raffinose monoesters prepared in Examples 1-3 did not change significantly during the 15-day test, indicating that the synthesized long-chain unsaturated fatty acid raffinose monoesters inhibited the oxidation of unsaturated fatty acids.

[0121] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A long-chain unsaturated fatty acid raffinose monoester, characterized in that Its structural formula is shown below: Wherein, R is a C18-C20 alkyl group.

2. The long-chain unsaturated fatty acid raffinose monoester according to claim 1, characterized in that Its structural formula is shown in formula (1), (2) or (3):

3. The method for preparing the long-chain unsaturated fatty acid raffinose monoester according to claim 1 or 2, characterized in that: The following steps are involved: Raffinose and unsaturated fatty acids are placed in a reaction container, dissolved in a solvent, and then a catalyst is added. The reaction is then heated under inert gas and stirring conditions. After the reaction is completed, the long-chain unsaturated fatty acid raffinose monoester is obtained by separation and purification.

4. The preparation method according to claim 3, characterized in that The molar ratio of raffinose to unsaturated fatty acid is 1:1-3; The mass ratio of the catalyst to raffinose is 1:

1.

5. The preparation method according to claim 3, characterized in that The unsaturated fatty acid is a fatty acid containing a C18 to C20 carbon chain.

6. The preparation method according to claim 3, characterized in that The fatty acid with a carbon chain of C18 to C20 is OA, ALA or EPA.

7. The preparation method according to claim 3, characterized in that The solvent is a tert-butyl alcohol / pyridine mixed solution; The catalyst is O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate.

8. The preparation method according to claim 3, characterized in that The heating reaction temperature is 45-65° C. and the time is 10-30 hours.

9. The preparation method according to claim 3, characterized in that The separation and purification method is column chromatography separation.

10. Use of the long-chain unsaturated fatty acid raffinose monoester according to claim 1 or 2 as a surfactant.

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