A method for extracting capsaicinoids by using a temperature-responsive deep eutectic solvent

Abstract

This invention discloses a method for preparing capsaicin-like substances by temperature-responsive eutectic solvent extraction, comprising the following steps: drying Yunnan chili peppers (after removing stems and seeds), pulverizing, sieving, and collecting the chili powder; mixing lidocaine (HBA) with six alkane-chain carboxylic acids (valerate, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, and lauric acid) at a 1:1 molar ratio to form a homogeneous and transparent liquid, TRDES; weighing the chili powder, adding it to the TRDES aqueous solution, and extracting by shaking; after extraction, centrifuging, and diluting the supernatant to obtain capsaicin-like substances. This invention uses temperature-responsive eutectic solvent extraction to prepare capsaicin-like substances, which is simple, highly efficient, and allows for the recycling of extraction reagents, effectively saving resources. It has significant practical and industrial value for promoting the large-scale production of capsaicin-like substances and enhancing their high-value applications.

Description

Technical Field

[0001] This invention relates to the extraction of capsaicin-like substances, specifically to a method for preparing capsaicin-like substances by extraction with a temperature-responsive eutectic solvent. Background Technology

[0002] Capsaicinoids are a class of alkaloids found in chili peppers, possessing a spicy flavor and various pharmacological activities. They mainly include capsaicin and dihydrocapsaicin, and are widely used in food additives, pharmaceutical analgesia, lacrimal agents, and agricultural pesticides. Existing methods for extracting capsaicinoids include traditional organic solvent extraction, which suffers from high solvent consumption, significant residues, low extraction rates, and environmental pollution, while also struggling to achieve high-purity separation. Supercritical carbon dioxide fluid extraction is expensive, has high operating costs, and consumes a lot of energy, making large-scale industrial application difficult. Ionic liquid extraction, while designable, suffers from poor biodegradability, unclear toxicity, and high costs associated with traditional ionic liquids. In terms of purification, conventional methods such as macroporous adsorption resin chromatography, silica gel column chromatography, or recrystallization are often cumbersome, have low yields, and require large amounts of volatile organic solvents for elution, making it difficult to balance environmental friendliness with high purity. In summary, existing extraction processes generally suffer from problems such as complex operation, high equipment requirements, cumbersome separation processes, and inability to recycle solvents. These issues fail to simultaneously meet the demands of industrial-scale production that balances extraction efficiency, product purity, production costs, and environmental friendliness, thus hindering the large-scale, efficient preparation and high-value application of capsaicin-like substances. Therefore, developing a method for preparing capsaicin-like substances that boasts high extraction efficiency, recyclable green solvents, simple operation, and high-purity products remains a pressing technical challenge in this field.

[0003] Eutectic solvents (DES), as a novel type of green solvent, are formed by hydrogen bond interactions between hydrogen bond acceptors and hydrogen bond donors. They possess significant advantages such as wide availability, low cost, low toxicity, and biodegradability, and have been widely applied in extraction, separation, and inorganic synthesis, gradually replacing traditional organic solvents to address environmental pollution issues. Temperature-responsive eutectic solvents (TRDES), an important branch of eutectic solvents, are switchable eutectic solvents with temperature-responsive characteristics. They undergo reversible phase transitions within a specific temperature range, requiring no additional reagents; the conversion between homogeneous and heterogeneous phases can be achieved simply by temperature control. In the field of natural active ingredient extraction, TRDES, with their environmentally friendly advantages and the potential for integrated extraction-separation due to temperature response, have gradually gained widespread attention. They effectively solve problems such as cumbersome separation, solvent residue, and loss of active ingredients in traditional solvent extraction processes, demonstrating promising application prospects in the efficient extraction and high-value preparation of plant active ingredients. They also provide new ideas and directions for overcoming technical bottlenecks in the extraction of capsaicin-like substances. Summary of the Invention

[0004] This invention uses a temperature-responsive eutectic solvent to extract capsaicin-like substances. The process is simple, the extraction efficiency is high, and the extraction reagents can be recycled, effectively saving resources.

[0005] This invention is achieved through the following technical solution: This invention discloses a method for preparing capsaicin-like substances by extraction with a temperature-responsive eutectic solvent, comprising the following steps: Raw material pretreatment: After removing the stems and seeds from the dried Yunnan hot pot chili peppers, they are pulverized by a high-speed multi-functional pulverizer, passed through an 80-mesh sieve, and the chili powder is collected, sealed, and stored at -20℃ away from light for later use.

[0006] Synthesis of a temperature-responsive eutectic solvent: Lidocaine (HBA) was mixed with six alkane-chain carboxylic acids (valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, and lauric acid) as HBDs in a 1:1 molar ratio in a round-bottom flask. The mixture was placed in a magnetic stirrer and stirred magnetically in an 80°C water bath for 60 min until a homogeneous and transparent liquid, TRDES, was formed. The prepared TRDES was then cooled to room temperature in a desiccator for later use. Preferably, the molar ratio of lidocaine to heptanoic acid in the TRDES was 1:1.

[0007] Extraction procedure: Accurately weigh an appropriate amount of chili powder into a 10 mL centrifuge tube, add a certain volume of TRDES aqueous solution, and extract by shaking. After extraction, centrifuge at 10000 rpm for 10 min, take the supernatant and dilute to obtain a mixture of capsaicin and dihydrocapsaicin. After filtration through a 0.22 μm filter membrane, perform high performance liquid chromatography analysis and calculate the capsaicin extraction rate Y (mg / g).

[0008] Preferably, the mass concentration of the TRDES aqueous solution is 20-80%. More preferably, the mass concentration of the TRDES aqueous solution is 30%.

[0009] Preferably, the solid-liquid ratio is 1:5-25 g / mL, the extraction temperature is 10-50 ℃, and the extraction time is 5-60 min; more preferably, the solid-liquid ratio is 1:10 g / mL, the extraction temperature is 30 ℃, and the extraction time is 20 min.

[0010] The present invention also includes heating the supernatant after separating capsaicin and dihydrocapsaicin, and separating the TRDES phase from the water at the minimum critical temperature (28°C), and then recovering it to achieve its recycling.

[0011] Beneficial effects: This invention uses a temperature-responsive eutectic solvent as the extraction medium. The solvent has a simple synthesis process, low cost, is non-toxic, harmless, biodegradable, and environmentally friendly. The extraction process is carried out under mild room temperature conditions, with no solvent volatilization or environmental pollution, which significantly improves the extraction efficiency of capsaicin-like substances and is superior to traditional ethanol systems and conventional organic solvent and ionic liquid extraction methods.

[0012] This invention leverages temperature-responsive characteristics to achieve efficient separation and purification through dilution, crystallization, and simple centrifugation, eliminating the need for complex chromatographic steps and significantly simplifying the process. The resulting product achieves a purity of over 96.5%. Simultaneously, the solvent can be rapidly recovered through heating and phase change, maintaining stability and efficiency even after six cycles, effectively reducing production costs and energy consumption. The overall process is simple to operate, requires conventional equipment, and is easily scaled up industrially. It balances high extraction rate, high purity, environmental friendliness, and economic efficiency, overcoming technical bottlenecks in existing technologies such as solvent residue, significant pollution, cumbersome separation, high costs, and difficulty in large-scale production. This provides a reliable solution for the efficient preparation and high-value application of capsaicin-like substances, and has significant practical and industrial value for promoting the large-scale production of capsaicin-like substances and enhancing their high-value application. Attached Figure Description

[0013] Figure 1 The effect of DES type on the extraction rates of capsaicin and dihydrocapsaicin; Figure 2 The effect of TRDES concentration on the extraction rates of capsaicin and dihydrocapsaicin; Figure 3 The effect of extraction temperature on the extraction efficiency of capsaicin and dihydrocapsaicin; Figure 4 The effect of extraction time on capsaicin extraction efficiency; Figure 5 The effect of solid-liquid ratio on the extraction efficiency of capsaicin and dihydrocapsaicin; Figure 6 This is a liquid chromatography chromatogram for capsaicin-based products. Figure 7 Comparison of capsaicin extraction from TRDES after 6 cycles. Detailed Implementation

[0014] The following examples further illustrate the above-described content of the present invention, but it should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention.

[0015] In the following embodiments: Determination of capsaicin and dihydrocapsaicin content: High-performance liquid chromatography (HPLC) was used. An Agilent 1260 Infinity II HPLC system equipped with a ZORBAX Eclipse Plus C18 column (4.6 × 250 mm, 5 μm) was employed. The mobile phase consisted of acidified water (0.1% formic acid, solvent A) and acetonitrile (solvent B), with a flow rate of 1.0 mL / min. The elution gradients were as follows: 0 min, 50% B; 3 min, 50% B; 10 min, 70% B; 12 min, 75% B; 15 min, 80% B; 18 min, 50% B; 20 min, 50% B. The flow rate was 1.0 mL / min, the column temperature was 30 °C, the detection wavelength was 280 nm, and the injection volume was 10 μL.

[0016] Calculate the capsaicin extraction rate Y (mg / g): = Capsaicin concentration in the extract (mg / mL) Volume of extract (mL) / Mass of shushuanla powder (g).

[0017] The present invention discloses a method for preparing capsaicin-like substances by extraction using a temperature-responsive eutectic solvent, comprising the following steps: Raw material pretreatment: After removing the stems and seeds from the dried Yunnan hot pot chili peppers, they are pulverized by a high-speed multi-functional pulverizer, passed through an 80-mesh sieve, and the chili powder is collected, sealed, and stored at -20℃ away from light for later use.

[0018] Synthesis of temperature-responsive eutectic solvents: Lidocaine (HBA) was mixed with six alkane-chain carboxylic acids (valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, and lauric acid) as HBDs in a 1:1 molar ratio in a round-bottom flask. The flask was placed in a magnetic stirrer (DF-101S, Zhengzhou Great Wall Science & Industry Co., Ltd., China) and magnetically stirred for 60 min in an 80°C water bath until a homogeneous and transparent liquid was formed. The prepared TRDES was then cooled to room temperature in a desiccator for later use.

[0019] Extraction procedure: Accurately weigh an appropriate amount of chili powder into a 10 mL centrifuge tube, add a certain volume of TRDES aqueous solution, and extract by shaking at a certain temperature for a certain time. After extraction, centrifuge at 10000 rpm for 10 min, take the supernatant, dilute it 10 times, filter it through a 0.22 μm filter membrane, and perform high-performance liquid chromatography (HPLC) analysis to calculate the capsaicin extraction rate Y (mg / g). The following parameters were optimized sequentially: TRDES type, TRDES concentration (10%-80%, w / w), extraction temperature (10-50℃), extraction time (5-60 min), and solid-liquid ratio (1:5-1:25 g / mL).

[0020] Example 1: Effect of DES type on the extraction rates of capsaicin and dihydrocapsaicin Six TR-DES were analyzed and compared with a 70% ethanol-water system to select the most suitable TR-DES for capsaicin and dihydrocapsaicin extraction. The experimental results are as follows: Figure 1 As shown in the figure. The results indicate that, overall, the eutectic solvent water system has a higher extraction rate than the ethanol-water system, and the capsaicin extraction rate first increases and then decreases with the increase of fatty acid carbon chain length. Among them, the lidocaine / heptanoic acid (1:1) TRDES system has the highest extraction efficiency. Under the conditions of 40% TRDES concentration, 30℃ shaking extraction for 60 min, and solid-liquid ratio of 1:10, the extraction rates of capsaicin and dihydrocapsaicin reached 38.5 mg / g and 12.31 mg / g, respectively, which were significantly higher than those of other TRDES systems (p<0.05).

[0021] Example 2: Effect of TRDES concentration on the extraction rates of capsaicin and dihydrocapsaicin Under the conditions of a fixed solid-liquid ratio of 1:10, an extraction temperature of 30℃, and an extraction time of 60 min, the effect of TRDES concentration (10-80 wt%) on the extraction rates of capsaicin and dihydrocapsaicin was investigated. The results are as follows: Figure 2 As shown, with increasing TRDES concentration, the extraction rates of capsaicin and dihydrocapsaicin both showed a trend of first increasing and then decreasing. The maximum values ​​of 39.05 mg / g and 12.33 mg / g, respectively, were reached at a TRDES concentration of 30%.

[0022] Example 3: Effect of extraction temperature on the extraction efficiency of capsaicin and dihydrocapsaicin Under the conditions of a fixed TRDES concentration of 30%, a solid-liquid ratio of 1:10, and an extraction time of 60 min, the effect of extraction temperature (10-50℃) on the extraction rates of capsaicin and dihydrocapsaicin was investigated. The results are as follows: Figure 3 As shown, the extraction rates of capsaicin and dihydrocapsaicin reached their highest values ​​at a temperature of 30℃, with extraction rates of 40.33 mg / g and 12.64 mg / g, respectively.

[0023] Example 4: Effect of extraction time on the extraction efficiency of capsaicin and dihydrocapsaicin Under the conditions of a fixed TRDES concentration of 30%, extraction temperature of 30℃, and solid-liquid ratio of 1:10, the effect of extraction time (5-60 min) on capsaicin extraction rate was investigated. The results are as follows: Figure 4 As shown, the extraction rates of capsaicin and dihydrocapsaicin increased rapidly within 5-20 min, and then basically reached equilibrium after 20 min. 20 min is the optimal extraction time, offering good economic efficiency and practicality.

[0024] Example 5: Effect of solid-liquid ratio on the extraction rates of capsaicin and dihydrocapsaicin Under the conditions of a fixed TRDES concentration of 30%, an extraction temperature of 30℃, and an extraction time of 20 min, the effect of the solid-liquid ratio (1:5-1:25 g / mL) on the extraction rates of capsaicin and dihydrocapsaicin was investigated. The results are as follows: Figure 5 As shown, the extraction rates of capsaicin and dihydrocapsaicin significantly increased with the solid-liquid ratio increasing from 1:5 to 1:10. When the solid-liquid ratio was further increased to 1:15 and 1:20, the extraction rates decreased slowly, and there was no significant difference between 1:25 and 1:15. Therefore, 1:10 g / mL was selected as the optimal solid-liquid ratio.

[0025] Taking all factors into account, under the conditions of a fixed TRDES concentration of 30%, an extraction temperature of 30℃, an extraction time of 20 min, and a solid-liquid ratio of 1:10 g / mL, the extraction rates of capsaicin and dihydrocapsaicin reached 39.95 mg / g and 12.65 mg / g, respectively.

[0026] Example 6: Preparation of capsaicin products and recycling of TRDES After extraction, the recovery and reuse capabilities of TRDES were investigated. Diluting the extract to 5% resulted in the precipitation of capsaicin and dihydrocapsaicin from the extraction solvent. After centrifugation, the precipitated solid powder was reconstituted with ethanol, filtered through a membrane, and analyzed by high-performance liquid chromatography (HPLC). Figure 6 The results showed that the precipitated product mainly contained capsaicin and dihydrocapsaicin, with a purity of over 96.5%. The supernatant was heated to a minimum critical temperature (28℃), at which point the TRDES phase separated from the water and was then recovered for recycling. The product was reused six times. Figure 7 As shown, the extraction rate of capsaicin decreases slowly with the increase of the number of TRDES cycles, indicating that the TR-DES has good recycling characteristics.

Claims

1. A method for preparing capsaicin-like substances by extraction with a temperature-responsive eutectic solvent, characterized in that, Includes the following steps: (1) Raw material pretreatment: Remove the stems and seeds from the dried Yunnan hot pot chili peppers, crush them, sieve them, and collect the chili powder; (2) Synthesis of temperature-responsive eutectic solvent: Lidocaine HBA was mixed with six alkane chain carboxylic acids, namely valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid and lauric acid, in a 1:1 molar ratio to form a uniform and transparent liquid TRDES. (3) Extraction steps: Weigh chili powder, add TRDES aqueous solution, shake to extract, centrifuge after extraction, and dilute the supernatant to obtain capsaicin-like substances.

2. The method for preparing capsaicin-like substances by extraction using a temperature-responsive eutectic solvent according to claim 1, characterized in that, The steps include: TRDES is: lidocaine to heptanoic acid in a molar ratio of 1:

1.

3. The method for preparing capsaicin-like substances by extraction using a temperature-responsive eutectic solvent according to claim 1, characterized in that, The mass concentration of TRDES aqueous solution is 20-80%.

4. The method for preparing capsaicin-like substances by extraction using a temperature-responsive eutectic solvent according to claim 3, characterized in that, The mass concentration of the TRDES aqueous solution is 30%.

5. The method for preparing capsaicin-like substances by extraction using a temperature-responsive eutectic solvent according to claim 1, characterized in that, The solid-liquid ratio was 1:5-25 g / mL, the extraction temperature was 10-50 ℃, and the extraction time was 5-60 min.

6. The method for preparing capsaicin-like substances by extraction using a temperature-responsive eutectic solvent according to claim 5, characterized in that, The solid-liquid ratio was 1:10 g / mL, the extraction temperature was 30 ℃, and the extraction time was 20 min.

7. A method for preparing capsaicin-like substances by extraction using a temperature-responsive eutectic solvent according to any one of claims 1-6, characterized in that, It also includes heating the supernatant after separating capsaicin and dihydrocapsaicin, separating the TRDES phase from the water under the minimum critical temperature condition, and then recovering it to achieve its recycling.

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