Curcumin-loaded oleogels and methods of making the same

Abstract

This invention discloses a curcumin-loaded oleogel and its preparation method. The method includes: extracting nanocellulose from pineapple leaves, compounding it with chitosan, and freeze-drying to prepare a chitosan / nanocellulose composite aerogel; dissolving curcumin in edible oil to obtain a curcumin-containing oil phase solution; immersing the composite aerogel in the oil phase solution and shaking to adsorb excess oil from the surface, thus obtaining the curcumin-loaded oleogel. The composite aerogel prepared by this invention forms a dense network structure internally, exhibiting excellent oil absorption (16.20 g / g) and oil retention (68.57%). The obtained oleogel has a curcumin loading rate as high as 52.24%, can achieve sustained release in a simulated gastrointestinal environment, and has good antioxidant activity, with a DPPH free radical scavenging rate of 75.24% after 14 days of storage. This invention provides a new solution for functional oil substitutes and the delivery of bioactive substances.

Description

Technical Field

[0001] This invention relates to the field of oleogel preparation technology, and in particular to an oleogel loaded with curcumin and its preparation method. Background Technology

[0002] With increasing consumer awareness of health, the food industry urgently needs to find new structural materials to replace solid fats rich in saturated and trans fatty acids. Oil gels, due to their ability to solidify liquid vegetable oils and their similar physicochemical properties and texture to solid fats, are considered one of the most promising alternatives.

[0003] The preparation methods of oleogels are mainly divided into direct methods and indirect methods. Direct methods usually involve heating processes, which can easily lead to the degradation of heat-sensitive active substances. Indirect methods, especially those using aerogels as templates, have attracted widespread attention due to their mild conditions and high controllability. Aerogels have a three-dimensional network structure with high specific surface area and high porosity, which can efficiently adsorb oils and can also serve as carriers for loading and delivering bioactive substances.

[0004] Chitosan is a natural cationic polysaccharide with good biocompatibility and film-forming properties, making it a commonly used material for aerogel preparation. However, pure chitosan aerogels have poor mechanical strength and are prone to structural collapse. Cellulose nanoparticles, with their high aspect ratio, high strength, and abundant surface hydroxyl groups, are often used as reinforcing phases. Combining these two materials holds promise for constructing more stable and superior aerogel templates through intermolecular interactions.

[0005] Curcumin is a polyphenolic compound derived from turmeric, possessing various physiological activities such as antioxidant and anti-inflammatory properties. However, its poor water solubility, sensitivity to light and heat, and low bioavailability limit its application in the food and pharmaceutical fields. Therefore, developing a carrier system that can effectively protect, deliver, and control the release of curcumin is of great significance. Summary of the Invention

[0006] The purpose of this invention is to provide a curcumin-loaded oleogel and its preparation method. The method utilizes pineapple leaf nanocellulose and chitosan to construct a composite aerogel template, and prepares the oleogel by adsorbing the curcumin-containing oil phase. The resulting product has high loading rate, good rheological properties and sustained-release antioxidant properties.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for preparing a curcumin-loaded oleogel includes the following steps: S1: Preparation of pineapple leaf nanocellulose: Pineapple leaf powder was subjected to alkali treatment and bleaching treatment in sequence to obtain pineapple leaf cellulose; then the pineapple leaf cellulose was oxidized by TEMPO oxidation system, and then ultrasonically crushed and freeze-dried to obtain pineapple leaf nanocellulose; S2: Preparation of chitosan / nanocellulose composite aerogel: The nanocellulose obtained in step 1 is dispersed in acetic acid solution, chitosan is added and stirred to dissolve, and a gel solution is obtained; the gel solution is pre-frozen and freeze-dried to obtain chitosan / nanocellulose composite aerogel. S3: Preparation of curcumin-loaded oil phase: Curcumin was dissolved in edible oil to obtain an oil phase solution containing curcumin; S4: Preparation of oleogel: The composite aerogel obtained in S2 is immersed in the oil phase solution of S3, and the aerogel is shaken to adsorb and remove excess oil from the surface to obtain the oleogel loaded with curcumin.

[0008] More preferably, the alkaline treatment in S1 is a treatment with sodium hydroxide solution; the bleaching treatment is a treatment with a mixed solution of hydrogen peroxide and sodium hydroxide; and the TEMPO oxidation system includes 2,2,6,6-tetramethylpiperidoxy, sodium bromide and sodium hypochlorite.

[0009] More preferably, the acetic acid solution in S2 has a mass fraction of 2%.

[0010] More preferably, the mass ratio of chitosan to nanocellulose in S2 is 8:2 to 2:8.

[0011] More preferably, the mass ratio of chitosan to nanocellulose in S2 is 4:6.

[0012] More preferably, the pre-freezing temperature in step S2 is -20°C and the time is 12 hours; the freeze-drying process also includes a step of freezing at -80°C for 4 hours.

[0013] More preferably, the edible oil in S3 is peanut oil.

[0014] More preferably, the conditions for the oscillation adsorption in S4 are room temperature, protection from light, and oscillation at 100 rpm for 12 h.

[0015] The present invention also provides a curcumin-loaded oleogel, prepared by the preparation method according to any one of claims 1 to 8.

[0016] More preferably, the oleogel has a curcumin loading rate of not less than 48%.

[0017] In summary, the present invention has the following beneficial effects: Firstly, the raw materials are widely available and environmentally friendly: This invention utilizes pineapple leaves, an agricultural waste, to extract nanocellulose, achieving high-value utilization of biomass resources, and the preparation process is green and environmentally friendly.

[0018] Secondly, the structure is controllable and the performance is excellent: By adjusting the ratio of chitosan to nanocellulose, this invention can construct a composite aerogel with a dense network structure. This aerogel has a high oil absorption capacity (up to 16.20 g / g) and a high oil retention rate (up to 68.57%), providing an ideal template for loading oils and active substances.

[0019] Thirdly, high loading rate and good sustained-release performance: The oleogel prepared by this invention using the composite aerogel as a template has a curcumin loading rate as high as 52.24%. In vitro digestion and antioxidant experiments show that the oleogel can protect curcumin, achieve sustained release in a simulated gastrointestinal environment, and maintain its antioxidant activity.

[0020] Fourth, the rheological properties are adjustable: by changing the composite ratio, this invention can obtain oleogels with different rheological properties, ranging from heat-softening elastic materials to heat-resistant viscoelastic materials, to meet different processing and application requirements.

[0021] Fifth, good acid resistance: The introduction of nanocellulose into the composite aerogel of this invention significantly improves the acid resistance of the oleogel in gastric juice, which is beneficial to the targeted release of curcumin in the intestine. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation process of curcumin-loaded oleogel in an embodiment of the present invention.

[0023] Figure 2 These are macroscopic photographs of aerogels with different chitosan ratios in embodiments of the present invention.

[0024] Figure 3 The images shown are scanning electron microscope (SEM) images of different aerogels in the embodiments of the present invention, wherein (a) CS, (b) CS / CNF-80%, (c) CS / CNF-60%, (d) CS / CNF-40%, (e) CS / CNF-20%, and (f) CNF.

[0025] Figure 4 The images show the infrared spectrum (a) and X-ray diffraction pattern (b) of different aerogels in the embodiments of the present invention.

[0026] Figure 5 The figures show the stress-strain curves of different aerogels in the embodiments of the present invention.

[0027] Figure 6 The figures show the test results of oil absorption (a) and oil retention (b) of different aerogels in the embodiments of the present invention.

[0028] Figure 7 These are optical microscope images of different oleogels in the embodiments of the present invention, wherein (a) CS, (b) CS / CNF-80%, (c) CS / CNF-60%, (d) CS / CNF-40%, and (e) CS / CNF-20%.

[0029] Figure 8 The rheological properties of different olegels in the embodiments of the present invention are shown in the figure, where (a) is a frequency scan and (b) is a temperature scan.

[0030] Figure 9 This is a graph showing the loading rate of curcumin on different oleogels in the embodiments of the present invention.

[0031] Figure 10 The figures show the in vitro digestion release rate (a) and antioxidant activity (b, c) of the oleogel in this embodiment of the invention. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the accompanying drawings.

[0033] Example 1: A curcumin-loaded oleogel and its preparation method, as follows... Figure 1 As shown, the specific steps are as follows: 1. Preparation of pineapple leaf nanocellulose: Wash, dry, and crush the pineapple leaves, then pass them through a 100-mesh sieve to obtain pineapple leaf powder.

[0034] Take 100 g of pineapple leaf powder, add 2000 mL of 3 wt% NaOH solution, digest at 80℃ for 2 h, wash with deionized water until neutral, and repeat twice.

[0035] The product after alkali treatment was added to a mixed solution of H2O2 and NaOH (weight ratio 10:1) at a solid-liquid ratio of 1:20 g / mL, bleached at 80℃ for 1 h, filtered, washed, and dried to obtain pineapple leaf cellulose.

[0036] Dissolve 1 mmol TEMPO and 1 mmol NaBr in 100 mL of distilled water, add 1 g of pineapple leaf cellulose, and stir well. Slowly add a 5 wt% NaClO solution adjusted to pH 10 with 0.1 M HCl, and react at room temperature. Maintain the pH of the reaction system at 10 with 0.5 mol / L NaOH until the pH remains constant. Filter and wash until neutral.

[0037] The above product was dispersed in water and treated with a cell ultrasonic disruptor to obtain a nanofiber suspension. The suspension was then freeze-dried for 48 h to obtain pineapple leaf nanocellulose.

[0038] 2. Preparation of chitosan / cellulose nanocomposite aerogel: Pineapple leaf nanocellulose was dispersed in a 2 wt% acetic acid solution and magnetically stirred at room temperature for 20 min.

[0039] Chitosan was added to the above nanocellulose-acetic acid solution in different mass ratios, and the solution was magnetically stirred for 30 min until completely dissolved to obtain a translucent gel solution. In this embodiment, the mass ratio of chitosan to nanocellulose was set to 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100, respectively, and the corresponding samples were labeled as CS, CS / CNF-80%, CS / CNF-60%, CS / CNF-40%, CS / CNF-20%, and CNF.

[0040] The gel solution was injected into a mold, pre-frozen at -20°C for 12 h, then frozen at -80°C for 4 h, and finally freeze-dried to obtain the composite aerogel.

[0041] 3. Preparation of curcumin-loaded oleogloss: 100 mg of curcumin was dissolved in peanut oil to prepare an oil phase containing curcumin.

[0042] Accurately weigh 10 mg of the composite aerogel prepared in step 2 and immerse it in the oil phase described above.

[0043] Shake at 100 rpm for 12 h in the dark at room temperature.

[0044] The adsorbed aerogel was suspended in a centrifuge tube for 30 minutes, excess peanut oil was drained off, and the surface residual oil was wiped off with filter paper to obtain the curcumin-loaded oil gel.

[0045] Example 2: Performance Testing and Result Analysis 1. Structural characterization The aerogel prepared in the experiment appeared as a swollen sponge block, such as... Figure 2 As shown in the figure, from a macroscopic perspective, pure chitosan aerogel is white, relatively soft, and exhibits slight deformation at the top edge; while pure cellulose aerogel has poor mechanical properties, contains cellulose fragments, and is soft and difficult to shape. In contrast, the aerogel composed of chitosan and nanocellulose (CS / CNF-80%) maintained an intact aerogel state without significant deformation or fragmentation, indicating that the composite aerogel can effectively improve the structural stability and mechanical strength of single-component aerogels.

[0046] SEM image analysis revealed that the microstructure of aerogels is closely related to their composition. Figure 3 The results show that pure chitosan aerogel ( Figure 3 a) exhibits a layered, stacked skeletal structure, while pure nanocellulose aerogel ( Figure 3f) exhibits a collapsed, blocky structure. When chitosan is combined with nanocellulose, the structure of the aerogel changes significantly. With increasing chitosan content, the composite aerogel ( Figure 3 (be) gradually forms a regular network structure, at a chitosan content of 80% ( Figure 3 At step b), the structural uniformity and compactness of the aerogel reach a stable state. This indicates that the introduction of CNF helps promote the formation of network structures in the composite aerogel.

[0047] FT-IR spectra of different aerogels, such as Figure 4 As shown in figure a. Each sample was at 3400 cm⁻¹. -1 Broad absorption bands appeared in the vicinity, which is due to the stretching vibration of the -OH functional group. The CNF after oxidation treatment showed a peak at 1730 cm⁻¹. -1 The appearance of a new -COOH absorption peak indicates that the TEMPO oxidation system can oxidize some of the hydroxyl groups into more reactive carboxyl groups. As the chitosan content increases, the absorption peak of this functional group gradually weakens and basically disappears when the ratio is above 60%, indicating that the carboxyl group has been completely cross-linked with the amino group of chitosan at this point.

[0048] Figure 4 Figure b shows the XRD patterns of different samples. As can be seen from the figure, pure chitosan has a distinct diffraction peak at 2θ = 20.1°. PL and CNF have two diffraction peaks at 2θ = 15.8° and 2θ = 22.1°, respectively, which are typical of type I cellulose. In the composite aerogel, the intensity of the diffraction peaks at 2θ = 15.8° and 2θ = 22.1° gradually increases with the increase of CNF, indicating that the nanocellulose and chitosan are bound together through electrostatic, hydrogen bonding, and physical entanglement.

[0049] 2. Mechanical property analysis Figure 5 The figures show the stress-strain curves for different aerogels. As can be seen from the figures, the CS / CNF-80% aerogel exhibits strong compressive strength and a high critical stress point, indicating that the mechanical properties of the material are improved at this ratio. The low critical stress values ​​of other aerogels are mainly due to the lack of plastic deformation capacity of the aerogel skeleton and the uneven distribution of pore structure, making the skeleton prone to fracture and collapse under stress.

[0050] 3. Oil absorption and retention capacity The aerogel was soaked in peanut oil for 24 hours and then weighed. The oil absorption capacity (Q_oil) of the aerogel was calculated using the following formula: In the formula, ma represents the initial mass of the aerogel, and m represents the mass of the resulting oleogel.

[0051] After centrifuging the aerogel at 10,000 rpm for 15 min, the sample was transferred to filter paper to remove excess oil, and then weighed. Oil removal was considered complete when the mass change of the oil gel sample after multiple centrifugations was <0.02 g. The oil retention rate of the aerogel was calculated using the following formula: In the formula, m1 and m2 represent the mass of the oleogel before and after centrifugation, respectively, and m0 represents the initial mass of the aerogel.

[0052] The oil absorption properties of aerogels are closely related to their internal structure. For example... Figure 6 As shown in Figure a, the oil absorption capacity of the composite aerogel first increases and then decreases with the increase of cellulose content. When the CNF content is moderate, a relatively uniform porous structure is formed inside the composite aerogel, which is conducive to the adsorption of the oil phase, so that the CS / CNF-40% aerogel exhibits excellent oil absorption capacity, reaching 16.20 ± 1.04 g / g.

[0053] The oil-holding capacity of oleogels was evaluated by high-speed centrifugation, and the results are as follows: Figure 6 As shown in b, unlike its oil absorption capacity, its oil retention capacity decreases with increasing nanocellulose content. The highest oil retention capacity, reaching 68.57%, is achieved when the chitosan content in the aerogel is 80%.

[0054] 4. Microstructure of olegels The microstructure of the prepared olegel was observed using an optical microscope, such as... Figure 7 As shown, the oleogels prepared using aerogels as templates exhibit different microstructural features. Pure chitosan aerogel ( Figure 7 a) The surface is smooth and flat, with many unbound oil droplets around it. As the chitosan content decreases, CS / CNF-40% ( Figure 7 d) CS / CNF-20% Figure 7 e) The aerogel has a cotton-like appearance, and the oil phase can effectively adhere to and be trapped in the aerogel, enhancing the aerogel's adsorption performance.

[0055] 5. Rheological properties of olegels The rheological properties of the oleogels were evaluated using a MARS60 rheometer. Frequency sweeps were performed at 0.1% strain and within a test range of 0.1–15 Hz to determine the storage modulus Gˊ and loss modulus G″ at room temperature. Temperature sweeps were performed in the range of 25–80 °C to determine the relationship between the linear viscoelastic range and the phase transition temperature of the oleogels.

[0056] The rheological properties of oleogels reflect their solid properties, such as... Figure 8As shown in Figure a, when the storage modulus Gˊ exceeds the loss modulus G″, it indicates that the reversible deformation of the oleogel sample is greater than the irreversible deformation, suggesting that it possesses gel-like properties. With the increase of nanocellulose content, the difference between the Gˊ and G″ values ​​gradually narrows. Based on the above analysis, with the decrease of nanocellulose content, both Gˊ and G″ values ​​show an upward trend, indicating that the higher the chitosan content, the better the viscoelastic properties of the oleogel.

[0057] In addition to frequency scanning, temperature scanning was also performed on the samples to study the structural changes of oleogel at high temperatures. Figure 8 b shows the changes in Gˊ and G″ values ​​of the five oleogels during heating from 25℃ to 80℃. Pure chitosan aerogel begins to undergo a phase transition at 50℃, while the modulus of the composite aerogel decreases more slowly, especially the CS / CNF-20% curve, which shows the flattest change. This indicates that nanocellulose has better heat resistance than chitosan, and increasing the nanocellulose content can significantly increase the thermal phase transition temperature of the composite oleogels.

[0058] 6. Curcumin loading rate To determine the curcumin content in the oleogel, an ethanol solution was added to the oleogel, and the mixture was treated with ultrasonic power at 60% for 20 min. The solution was then diluted, and the absorbance was measured at 430 nm. The curcumin content in the oleogel was calculated using a curcumin standard curve. The curcumin loading rate was calculated using the following formula: In the formula, m1 is the mass of curcumin measured after the above treatment; m2 is the amount of curcumin added during the preparation of the oleogel.

[0059] The loading effects of the five oleogels prepared in the experiment on curcumin are as follows: Figure 9 As shown, all five oleogels exhibited high loading rates for curcumin, ranging from 48.99% to 54.88%. The aerogel demonstrated a significant loading capacity for curcumin in peanut oil, attributed to its excellent oil absorption and retention properties and uniformly distributed pore structure.

[0060] 7. Release rate and antioxidant activity of curcumin in oleogels (1) An in vitro simulated digestion experiment was conducted to study the release rate of curcumin oil gel in gastric and intestinal fluids. Gastric and intestinal fluids were prepared according to the artificial gastric and intestinal fluids in the Chinese Pharmacopoeia. 10 mg of curcumin oil gel sample was mixed with 15 mL of gastric fluid, and the pH was adjusted to 2.5. The mixture was then shaken at 120 rpm for 2 h in a constant temperature water bath at 37 ℃. After digestion, the pH of the solution was adjusted to 7.0 to terminate the gastric reaction. The mixture from the gastric phase was then added to an equal volume of intestinal fluid, and the pH of the solution was 7.6. The intestinal experiment was simulated at 37 ℃.

[0061] Oil gels containing curcumin release were collected after 3 h. To extract the supernatant, 3 mL of ethanol solution was added to the sample, followed by centrifugation at 10000 pm for 10 min. The concentration of curcumin in the supernatant was determined at 430 nm using a full-wavelength microplate reader, and its release rate (Qrelease) was calculated using the following equation: In the formula, C is the concentration of curcumin in the supernatant, and C0 is the concentration of curcumin in an equal amount of peanut oil.

[0062] The curcumin release rate of the prepared composite oleogel during simulated gastric and intestinal digestion was as follows: Figure 10 As shown in Figure a, during the gastric digestion stage, the pure chitosan oleogel suffers severe structural damage due to the decomposition of the substrate into small molecules in an acidic environment. In contrast, the curcumin in the composite oleogel is released along with the overflow of peanut oil, and the material remains intact after intestinal digestion, with a curcumin release rate of 89.89 ± 0.96%.

[0063] (2) The antioxidant activity of the oleogel was determined using the DPPH free radical scavenging method. 5 mg of oleogel was mixed with 5 mL of 0.1 mM DPPH / ethanol solution, and the mixture was shaken for 15 s and then protected from light for 3 h. The absorbance of the solution was then measured at 517 nm, with ethanol used as a blank control. The DPPH free radical scavenging activity (RSA%) was calculated using the following equation: In the formula: A0 is the absorbance of the blank solution; A1 is the absorbance of the DPPH free radical solution after the addition of oleogel.

[0064] The DPPH free radical scavenging capacity of each group of oleogels was measured on days 0, 7, and 14 to evaluate the sustained-release capacity of the oleogels for curcumin. Figure 10 As shown in b, the activity of curcumin on the surface of the curcumin-coated oleogel gradually decreased with prolonged storage time and exposure to natural light. The reaction time of the oleogel with DPPH was delayed by 7 days and 14 days (as shown in b). Figure 10 c) The highest clearance rate of oleogel was found to be 75.24 ± 1.85%. This indicates that the layered structure inside the aerogel can effectively block the entry of oxygen, preventing curcumin from being rapidly oxidized, and allowing curcumin to be released slowly and exert its effect.

[0065] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing a curcumin-loaded oleogel, characterized in that, Includes the following steps: S1: Preparation of pineapple leaf nanocellulose: Pineapple leaf powder was subjected to alkali treatment and bleaching treatment in sequence to obtain pineapple leaf cellulose; then the pineapple leaf cellulose was oxidized by TEMPO oxidation system, and then ultrasonically crushed and freeze-dried to obtain pineapple leaf nanocellulose; S2: Preparation of chitosan / nanocellulose composite aerogel: The nanocellulose obtained in step 1 is dispersed in acetic acid solution, chitosan is added and stirred to dissolve, and a gel solution is obtained; the gel solution is pre-frozen and freeze-dried to obtain chitosan / nanocellulose composite aerogel. S3: Preparation of curcumin-loaded oil phase: Curcumin was dissolved in edible oil to obtain an oil phase solution containing curcumin; S4: Preparation of oleogel: The composite aerogel obtained in S2 is immersed in the oil phase solution of S3, and the aerogel is shaken to adsorb and remove excess oil from the surface to obtain the oleogel loaded with curcumin.

2. The method for preparing a curcumin-loaded oleogel according to claim 1, characterized in that: The alkaline treatment in S1 is performed using a sodium hydroxide solution; the bleaching treatment is performed using a mixed solution of hydrogen peroxide and sodium hydroxide; the TEMPO oxidation system includes 2,2,6,6-tetramethylpiperidoxy, sodium bromide, and sodium hypochlorite.

3. The method for preparing a curcumin-loaded oleogel according to claim 1, characterized in that: The acetic acid solution in S2 has a mass fraction of 2%.

4. The method for preparing a curcumin-loaded oleogel according to claim 1, characterized in that: The mass ratio of chitosan to nanocellulose in S2 is 8:2 to 2:

8.

5. The method for preparing a curcumin-loaded oleogel according to claim 4, characterized in that: The mass ratio of chitosan to nanocellulose in S2 is 4:

6.

6. The method for preparing a curcumin-loaded oleogel according to claim 1, characterized in that: The pre-freezing temperature in S2 is -20℃ and the time is 12h; the freeze-drying process also includes a step of freezing at -80℃ for 4h.

7. The method for preparing a curcumin-loaded oleogel according to claim 1, characterized in that: The edible oil mentioned in S3 is peanut oil.

8. The method for preparing a curcumin-loaded oleogel according to claim 1, characterized in that: The conditions for the oscillation adsorption in S4 are: room temperature, protection from light, and oscillation at 100 rpm for 12 h.

9. An oleogel loaded with curcumin, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. The curcumin-loaded oleogel according to claim 9, characterized in that: The oleogel has a curcumin loading rate of not less than 48%.

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