A method for efficiently preparing ellagic acid from rose processing by-products

Abstract

The application discloses a method for efficiently preparing ellagic acid from rose processing by-products, and belongs to the technical field of reusing agricultural product processing by-products. The method uses rose waste residues accompanying essential oil production as raw materials, and uses NADES to extract ellagic acid in the rose waste residues. In combination with Guassian calculation, 28 DES combinations are screened. Among them, choline chloride-urea performs best in actual extraction experiments. The extraction conditions are optimized as follows: the molar ratio of choline chloride-urea is 1:2, the water content is 30 wt%, the solid-liquid ratio is 1:50 g / mL, the ultrasonic condition is that the time is 30 min, the power is 288 W, and the temperature is 80 DEG C. The application also explores the influence of the drying temperature of the flower residues on the content of ellagic acid, and finds that when the drying temperature is 120 DEG C, ellagic acid can be better released, and the extraction amount of the final ellagic acid can reach 27.06+ / -0.41 mg / g of dry flower residues, and the purity after extraction can reach 60%.

Description

Technical Field

[0001] This invention belongs to the field of agricultural product processing by-product recycling technology, specifically a method for efficiently preparing ellagic acid from rose processing by-products. Background Technology

[0002] Ellagic acid is a natural polyphenolic compound formed by the oxidative coupling of gallic acid units. Its molecular structure contains four phenolic hydroxyl groups and two lactone rings, giving it strong hydrogen and electron donor capabilities. Studies have shown that ellagic acid exhibits significant free radical scavenging ability in various in vitro antioxidant models. Furthermore, cell and animal experiments have demonstrated that ellagic acid possesses antioxidant, anti-inflammatory, and antitumor biological activities, and shows promising effects in inhibiting melanin production and delaying photoaging. Therefore, ellagic acid has been widely used in the formulation of functional foods, health products, and cosmetics, and its efficient and stable acquisition is of great significance for practical production applications.

[0003] Ellagic acid is distributed in a variety of plants, but its content varies significantly among different plant sources. According to existing literature, pomegranate peel is considered one of the plant sources with the highest ellagic acid content, with total ellagic acid (including free and bound forms released after hydrolysis) reaching 30-60 mg / g dry weight. In addition, the ellagic acid content in berries such as raspberries and strawberries is typically between 1-10 mg / g dry weight. Research and applications regarding the sources of ellagic acid primarily focus on pomegranate peel, berry plants, and nut byproducts.

[0004] Ellagic acid exists primarily in plant tissues as tannins or esterified compounds. The development of high-content raw materials often relies on organic solvent extraction and strong acid hydrolysis, resulting in high solvent consumption, heavy environmental burden, high energy consumption, severe equipment corrosion, and complex post-processing. Natural deep eutectic solvents (NADES) are a class of designable solvent systems composed of naturally derived components. NADES can be directly used in food or cosmetic systems, reducing solvent removal and purification steps. However, due to the diverse constituent units and complex hydrogen bond networks of NADES, different solvent systems exhibit significant differences in their solubility and selectivity for target compounds. Existing research largely focuses on empirical screening of specific natural products or a few solvent combinations, lacking a systematic screening strategy guided by specific target compounds and incorporating molecular mechanisms of action. Summary of the Invention

[0005] [Technical Issues] The technical problem to be solved by this invention is that the main sources of ellagic acid are currently limited to pomegranate peel, berry plants and nut by-products, etc. However, existing methods for extracting ellagic acid mostly use organic solvent extraction or strong acid hydrolysis, which have low extraction efficiency, large solvent consumption, and operational safety and environmental problems, thus limiting its application in the food, cosmetics and other industries.

[0006] [Technical Solution] To address the aforementioned problems, this invention provides a method for the efficient preparation of ellagic acid from rose processing byproducts. This invention uses rose petal residue, a byproduct of essential oil production, as raw material and utilizes NADES solvent to extract ellagic acid from it. First, based on the molecular structure of ellagic acid and combined with Guassian calculations, 28 DES combinations were screened. The top five combinations from the calculations were then experimentally verified. The results showed that NADES1 (choline chloride-urea), with the best binding energy, also performed best in the actual extraction experiments. Furthermore, this invention investigated the effect of petal drying temperature on ellagic acid content, finding that drying at 120 °C resulted in better release of ellagic acid, providing a reference for petal processing. The final ellagic acid extraction yield reached 27.06 ± 0.41 mg / g of dried petal residue, with an unpurified purity of up to 60% after extraction.

[0007] This invention provides a method for efficiently preparing ellagic acid from rose processing byproducts, comprising the following steps: (1) In one embodiment of the present invention, the process of preparing rose waste residue is as follows: using fresh roses as raw materials, the essential oil is distilled by steam distillation, the amount of roses and deionized water is 200 g and 400 g respectively, the distillation time is 4-8 h (starting from the boiling of water), and after the distillation, the flower residue is dried and ground into powder to obtain rose residue. (2) Next, density functional theory (DFT) calculations were performed using Guassian to theoretically analyze the interaction energy between ellagic acid and different NADES, and to screen NADES solvent combinations. (3) Prepare NADES solvent, add water, and after preparation, mix rose residue with NADES and extract by ultrasound.

[0008] In one embodiment of the present invention, in step (1), the drying conditions are 50-140 °C, more preferably 120 °C.

[0009] In one embodiment of the present invention, in step (2), the hydrogen bond acceptor HBA includes: choline chloride and betaine; the hydrogen bond donor HBD includes: glycine, proline, fructose, glucose, sucrose, xylitol, glycerol, lactic acid, malic acid, citric acid, p-hydroxybenzoic acid, p-coumaric acid, p-hydroxybenzaldehyde, and urea; the 28 NADES solvent combinations include: choline chloride-urea, choline chloride-p-coumaric acid, choline chloride-p-hydroxybenzaldehyde, choline chloride-lactic acid, betaine-glycerol, choline chloride-citric acid, and choline chloride-glycerol. Betaine-p-hydroxybenzaldehyde, betaine-proline, betaine-p-coumaric acid, betaine-glycine, choline chloride-sucrose, betaine-urea, choline chloride-fructose, betaine-sucrose, betaine-citric acid, betaine-p-hydroxybenzoic acid, betaine-malic acid, choline chloride-proline, betaine-p-hydroxybenzoic acid, betaine-fructose, betaine-lactic acid, choline chloride-glycine, betaine-xylitol, choline chloride-malic acid, choline chloride-p-hydroxybenzoic acid, choline chloride-xylitol, choline chloride-sucrose.

[0010] In one embodiment of the present invention, in step (3), the NADES solvent includes: choline chloride-urea, choline chloride-lactic acid, and betaine-glycerol; more preferably, choline chloride-urea.

[0011] In one embodiment of the present invention, in step (3), the molar ratio of choline chloride to urea is 2:1 to 1:8, and more preferably 1:2.

[0012] In one embodiment of the present invention, in step (3), the water content of choline chloride-urea is 0-50 wt%, more preferably 30 wt%.

[0013] In one embodiment of the present invention, in step (3), the ratio of rose petal residue to NADES liquid is 1:10-1:90 g / mL, more preferably 1:50 g / mL.

[0014] In one embodiment of the present invention, in step (3), the ultrasonic power is 0-480 W, more preferably 288 W.

[0015] In one embodiment of the present invention, in step (3), the ultrasound time is 0-60 min, more preferably 30 min.

[0016] In one embodiment of the present invention, in step (3), the ultrasonic temperature is 25-80 ℃, more preferably 80 ℃.

[0017] [Beneficial Effects] (1) The key to this invention lies in using the distillation residue obtained after rose essential oil production as a novel source of high-content and high-purity ellagic acid for the first time, and on this basis, constructing a green and low-cost extraction method based on computationally assisted screening of natural deep eutectic solvents (NADES). This avoids the empirical screening approach of existing technologies for NADES. Based on the structural characteristics of ellagic acid molecules and their hydrogen bonding sites, a combination of theoretical calculations and experimental verification was used to screen out a NADES system with high affinity for ellagic acid. Further optimization of extraction conditions, including NADES ratio, water content, material-to-liquid ratio, and ultrasonic conditions (time, power, temperature), resulted in a final extraction yield of 27.06 ± 0.41 mg / g dried flower residue with a purity of 60%. The results show that compared with unextracted rose raw materials, the flower residue after essential oil extraction is significantly enriched in ellagic acid, and its content is significantly affected by the drying method and drying temperature. Flower residue treated at 120 ℃ exhibits the highest ellagic acid content. This invention not only clarifies the processing mechanism for the enrichment of ellagic acid in rose pomace, but also establishes a method that has the advantages of being green and environmentally friendly, having a simplified process, and high extraction efficiency, providing a new technical path for the resource-based acquisition of ellagic acid and the high-value utilization of rose essential oil by-products.

[0018] (2) This invention breaks through the existing understanding that ellagic acid mainly comes from traditional raw materials such as pomegranate peel and walnut peel, and provides a new idea for the high-value utilization of rose processing by-products.

[0019] (3) Green and environmentally friendly, with high solvent safety: The present invention uses NADES as the extraction medium. The solvent components are natural, low in toxicity and biodegradable. No traditional organic solvents are used in the extraction process. The resulting extract can be applied directly or after simple treatment to food, cosmetics and health products.

[0020] (4) Computation-assisted screening, wide-range screening: Density functional theory (DFT) calculations are introduced to analyze the interaction between ellagic acid and different NADES systems at the molecular level, which realizes the precise screening of solvent systems, avoids the blindness of traditional empirical screening, and improves the targeting of solvent selection and extraction efficiency.

[0021] (5) High extraction efficiency and mild process conditions: Based on theoretical screening and experimental optimization, this invention can achieve efficient extraction of ellagic acid under mild conditions. Compared with traditional organic solvent or strong acid hydrolysis methods, the extraction rate is higher, and the process steps are simplified and the operation is safe.

[0022] (6) Elucidate the influence mechanism of processing on ellagic acid enrichment: The variation law of ellagic acid content in the residue after essential oil extraction under different drying temperature conditions was investigated, revealing the influence of essential oil extraction process and subsequent processing conditions on ellagic acid enrichment behavior, providing a reference for industrial production. Attached Figure Description

[0023] Figure 1. Ellagic acid content in roses treated with different methods; Figure 2. Optimized ellagic acid molecule and the geometric configuration of HBD / HBA molecules constituting NADES; Figure 3. Stable configurations of the 28 optimized NADES groups, A represents choline chloride NADES; B represents betaine NADES. Figure 4. Binding energy thermograms of various NADES combinations in DFT calculations; Figure 5. Ellagic acid content extracted with different types of solvents. Different letters above the bars represent significant differences. Figure 6. Single-factor experiments in the extraction process. A is the single-factor experiment of HBA to HBD molar ratio; B is the single-factor experiment of NADES water content; C is the single-factor experiment of material-liquid ratio; D is the single-factor experiment of ultrasonic power; E is the single-factor experiment of ultrasonic time; F is the single-factor experiment of ultrasonic temperature. Different letters above the bars represent significant differences. Figure 7. Ellagic acid content extracted under optimal conditions. Different letters above the bars represent significant differences. Figure 8. Changes in ellagic acid content in rose pomace under different processing methods and drying temperatures. Different letters above the bars represent significant differences. Figure 9. Purity of ellagic acid in rose pomace at 120 ℃ drying temperature. Detailed Implementation

[0024] The reagents used in this invention were purchased from Aladdin Reagent Co., Ltd. (Aladdin, Shanghai), and include: (1) Choline chloride, CAS No.: 67-48-1; (2) Betaine, CAS No.: 107-43-7; (3) Urea, CAS No.: 57-13-6; (4) p-hydroxybenzoic acid, CAS No.: 99-96-7; (5) p-coumaric acid, CAS No.: 501-98-4; (6) p-hydroxybenzaldehyde, CAS No.: 123-08-0; (7) Lactic acid, CAS No.: 79-33-4; (8) Glycerol, CAS No.: 56-81-5; (9) Citric acid, CAS No.: 77-92-9; (10) Proline, CAS No.: 147-85-3; (11) Glycine, CAS No.: 56-40-6; (12) Sucrose, CAS No.: 57-50-1; (13) Fructose, CAS No.: 7660-25-5; (14) Glucose, CAS No.: 50-99-7; (15) Malic acid, CAS No.: 97-67-6; (16) Xylitol, CAS No.: 87-99-0.

[0025] The calculation method for the effect data mentioned in this invention is as follows: Ellagic acid extraction yield = ellagic acid content in dried rose pomace / mass of dried rose pomace, unit: mg / g; Extraction rate improvement rate = (Ellagic acid content extracted by NADES) Ellagic acid content extracted by other methods / Ellagic acid content extracted by other methods × 100%.

[0026] Example 1 The method for preparing rose petal residue in this invention: Fresh rose petals were used as raw material, and essential oil was distilled using steam distillation. The amounts of rose petals and deionized water were 200 g and 400 g, respectively, and the distillation time was 4-8 hours (starting from the time the water boiled). After distillation, the petal residue was dried in an oven at 50 °C. Once dried to constant weight, the residue was ground into powder, placed in sealed bags, and stored at -80 °C to obtain the dried petal residue sample.

[0027] In addition, fresh Pingyin roses were directly placed in an oven at 50 ℃ and dried until constant weight, then ground into powder to obtain dried pollen samples.

[0028] Next, 1 g of dried pollen, dried flower residue, and fresh flower samples ground under liquid nitrogen were weighed and added to 10 mL of anhydrous ethanol. The mixture was then extracted by sonication (room temperature, 288 W, 30 min). After extraction, the mixture was centrifuged (4000 rpm, 10 min), and 1 mL of the supernatant was filtered through a 0.22 μm filter membrane for HPLC detection. The HPLC detection method was as follows: an Agilent 1260 Infinity II high-performance liquid chromatography system (equipped with a G7111A quaternary pump) was used, with a UV detection wavelength of 254 nm; the column was a ZORBAX EclipsePlus C18 (4.6 mm × 250 mm, 5 μm); the column temperature was 30 ℃; mobile phase A was 0.1% (w / v) formic acid aqueous solution, and mobile phase B was acetonitrile; the flow rate was 1.0 mL / min; and the injection volume was 4 μL. Gradient elution program: 0–5 min, 5% B; 5–25 min, 5%→20% B; 25–35 min, 20%→40% B; 35–41 min, 40%→80% B; 41–45 min, 80% B; 45.01–50 min, 5% B. Simultaneously, a 100 ppm ellagic acid standard solution was prepared using chromatographic grade methanol and detected using the same method. The retention time of ellagic acid was approximately 29.3 min.

[0029] HPLC analysis revealed that ellagic acid was undetectable in Pingyin rose petals before essential oil extraction, while it was detected in dried Pingyin rose petals at relatively low levels. However, the ellagic acid content was significantly increased in the rose petal residue obtained after essential oil extraction (Figure 1). These results indicate that the high-temperature steam treatment during essential oil extraction induces the depolymerization and hydrolysis of ellagic tannins in rose petals, thereby releasing a large amount of ellagic acid.

[0030] Example 2 Based on the above findings, this invention combines computational simulation methods to screen and construct NADES solvents with excellent interaction capabilities with ellagic acid, targeting its molecular structural characteristics. Density Functional Theory (DFT) calculations were performed using Guassian to theoretically analyze the interaction energies between ellagic acid and different NADES. The screening covered 28 NADES combinations. Naturally derived hydrogen bond acceptors (HBAs) included choline chloride and betaine; naturally derived hydrogen bond donors (HBDs) included glycine, proline, fructose, glucose, sucrose, xylitol, glycerol, lactic acid, malic acid, citric acid, p-hydroxybenzoic acid, p-coumaric acid, p-hydroxybenzaldehyde, and urea (Figure 2). Small molecule configurations were optimized at the B3LYP-D3(BJ) / def2-SVP level, and energy calculations were performed at the B3LYP-D3(BJ) / def2-TZVP level. Next, using Molclus's gemmer component, 28 NADES and ellagic acid-DES cluster configurations (molar ratio 1:1) were constructed. 200 configurations were randomly generated, and initial optimization was performed at the PM6-DH+ level using MOPAC. The configuration with the lowest energy was then optimized at the M062X / 6-31G(d) level. Finally, the energy was calculated at the M062X / 6-311+G(d,p) level, yielding the BSSE-corrected binding energy. Figure 3 (Table 1). The more negative the binding energy value, the stronger the interaction between ellagic acid and the NADES system, and the more stable the complex system formed, which is more conducive to the dissolution and extraction of ellagic acid (Figure 4).

[0031] Table 1 shows the binding energy ranking of the 28 DES combinations.

[0032] HBA stands for hydrogen bond acceptor, and HBD stands for hydrogen bond donor. Example 3 Based on the prediction results of Example 2, NADES1 (choline chloride-urea) was used as the solvent.

[0033] Using the waste residue from rose essential oil production in Example 1 as raw material, NADES was prepared at a 1:1 molar ratio with a uniform water addition of 20 wt%. After preparation, the flower residue powder and NADES were mixed at a material-to-liquid ratio of 1:50 g / mL and extracted by sonication (30 min, 288 W, 25 °C). After extraction, the mixture was centrifuged (5000 rpm, 10 min), and the supernatant was diluted 10-fold with chromatographic grade methanol for HPLC analysis. The HPLC analysis method was as follows: an Agilent 1260 Infinity II high-performance liquid chromatography system (equipped with a G7111A quaternary pump) was used, with a UV detection wavelength of 254 nm; the column was a ZORBAX Eclipse Plus C18 (4.6 mm × 250 mm, 5 μm); the column temperature was 30 °C; mobile phase A was 0.1% (w / v) formic acid aqueous solution, and mobile phase B was acetonitrile; the flow rate was 1.0 mL / min; and the injection volume was 10 μL. Gradient elution program: 0–5 min, 5% B; 5–20 min, 5% → 80% B; 20–25 min, 80% B; 25.01–30 min, 5% B. The retention time of ellagic acid is approximately 16.5 min.

[0034] Example 4 The extraction steps and NADES preparation method were the same as in Example 3, except that the NADES solvents were changed to NADES2 (choline chloride-lactic acid) and NADES3 (betaine-glycerol), and the amounts and ratios of NADES2 and NADES3 were the same as in Example 3. Choline chloride-coumaric acid and choline chloride-hydroxybenzaldehyde, which ranked 2nd and 3rd in binding energy, were excluded because their HBD (coumaric acid and hydroxybenzaldehyde) structures have rigid conjugated planar structures, and the intermolecular hydrogen bonds cannot break the high lattice energy, thus failing to form NADES. As shown in Figure 5, among the three combinations that could successfully form NADES based on the prediction results of Example 2, NADES1 showed the best extraction effect.

[0035] Comparative Example 1 The extraction steps and NADES preparation method are the same as in Example 3, except that anhydrous ethanol, 70% ethanol, 1M HCl solution and NADES4 (choline chloride-citric acid) are used as controls.

[0036] Using the waste residue from the production of rose essential oil in Example 1 as raw material, the flower residue powder was mixed with anhydrous ethanol at a material-to-liquid ratio of 1:50 g / mL, and extracted by ultrasonication (time 30 min, power 288 W, 25 ℃).

[0037] Using the waste residue from the production of rose essential oil in Example 1 as raw material, the flower residue powder was mixed with 70% ethanol at a material-to-liquid ratio of 1:50 g / mL and extracted by ultrasonication (time 30 min, power 288 W, 25 ℃).

[0038] Using the waste residue from the production of rose essential oil in Example 1 as raw material, the flower residue powder was mixed with 1M HCl solution at a material-to-liquid ratio of 1:50 g / mL and extracted by ultrasonication (time 30 min, power 288 W, 25 ℃).

[0039] Using the waste residue from the production of rose essential oil in Example 1 as raw material, NADES (choline chloride-citric acid) was prepared at a 1:1 molar ratio, with a uniform water addition of 20 wt%. After preparation, the flower residue powder and NADES were mixed at a material-to-liquid ratio of 1:50 g / mL and extracted by ultrasonication (30 min, 288 W, 25 °C).

[0040] As shown in Figure 5, among all extraction reagents, 70% ethanol showed the best extraction effect, significantly higher than other solvents. Among the four NADES reagents, NADES1 (choline chloride-urea) and NADES2 (choline chloride-lactic acid), obtained through theoretical screening and experimental verification in this invention, showed significantly better extraction effects than NADES4 (choline chloride-citric acid), with NADES1 (choline chloride-urea) showing the best effect.

[0041] Comparative Example 2 The extraction steps and NADES preparation method were the same as in Example 3, with the only difference being the adjustment of the choline chloride-urea ratio (molar ratio 2:1-1:8). As shown in Figure 6A, NADES could not be formed when the molar ratio was 1:4-1:8, and NADES with a molar ratio of 1:3 precipitated crystals after one day. Within the molar ratio range of 2:1 to 1:4, the extraction yield of ellagic acid showed a trend of first increasing and then decreasing, with the best extraction effect at 1:2, indicating that the three-dimensional hydrogen bond network structure formed by choline chloride and urea was the most dense and stable at this ratio. When deviating from this ratio, insufficient hydrogen bond donors (2:1) led to increased viscosity and hindered mass transfer, while excessive donors (1:4-1:8) intensified urea self-association and precipitation, resulting in a decrease in extraction efficiency.

[0042] Comparative Example 3 The extraction steps and NADES preparation method are the same as in Example 3, with the only difference being the adjustment of the water content of the choline chloride-urea mixture (0-50 wt%), as shown in Figure 6B. At lower water content (0-10 wt%), the viscosity of NADES is higher, mass transfer is hindered, and the ellagic acid extraction yield is lower. As the water content increases by 20-40 wt%, the ellagic acid extraction yield shows an upward trend, reaching its maximum at 30 wt%. At a water content of 50 wt%, excessive water causes damage to the NADES structure, and the ellagic acid extraction yield begins to decline.

[0043] Comparative Example 4 The extraction steps and NADES preparation method were the same as in Example 3, with the only difference being the adjustment of the solid-liquid ratio (1:10-1:90 g / mL). As shown in Figure 6C, within the solid-liquid ratio range of 1:10-1:50 g / mL, the extraction yield of ellagic acid gradually increased, reaching the optimal extraction effect at 1:50 g / mL. When the solid-liquid ratio exceeded 1:50 g / mL, there was no significant difference in extraction yield, and it tended to plateau. The effective contact area between the pollen residue and NADES increased with the increase of the solid-liquid ratio, until 1:50 g / mL was the optimal critical point, and further increasing the solvent did not increase the absolute extraction yield.

[0044] Comparative Example 5 The extraction steps and NADES preparation method are the same as in Example 3, except that the ultrasonic power is adjusted (0-480W). As shown in Figure 6D, within the ultrasonic power range of 0-288W, the cavitation effect of ultrasound is enhanced with the increase of ultrasonic power, resulting in greater structural damage to the flower residue powder and higher ellagic acid extraction. The extraction amount reaches a plateau at 288W. After that, with the increase of ultrasonic power (288-480W), the increase in ellagic acid extraction amount is not significantly different from that at 288W, indicating that the power input of 288W is sufficient to achieve sufficient cell wall disruption and complete dissolution of ellagic acid.

[0045] Comparative Example 6 The extraction steps and NADES preparation method were the same as in Example 3, with the only difference being the adjustment of the ultrasonic time (10-60 min) (Figure 6). As shown in Figure 6E, extending the ultrasonic time within the range of 0-30 min continuously disrupted the plant matrix structure and enhanced solid-liquid mass transfer, causing ellagic acid to dissolve continuously, reaching its maximum value at 30 min. Further extending the ultrasonic time to 60 min did not show a significant difference in the amount of ellagic acid extracted compared to 30 min, indicating that 30 min was sufficient to achieve complete extraction.

[0046] Comparative Example 7 The extraction steps and NADES preparation method were the same as in Example 3, with the only difference being the adjustment of the ultrasonic temperature (40-80℃). As shown in Figure 6F, within the temperature range allowed by the ultrasonic instrument (40-80℃), the extraction amount of ellagic acid gradually increased with increasing temperature, reaching its optimal value at 80℃, indicating that high temperature during the extraction process is beneficial for the release of ellagic acid.

[0047] Example 5 Using the waste residue from the production of rose essential oil in Example 1 as raw material, NADES was prepared with choline chloride:urea = 1:2 molar ratio, and the amount of water added was uniformly 30 wt%. After preparation, the flower residue powder and NADES were mixed at a material-to-liquid ratio of 1:50 g / mL and extracted by ultrasonication (time 30 min, power 288 W, 80 ℃).

[0048] Comparative Example 8 The preparation method is the same as in Example 5, except that choline chloride:urea is replaced with anhydrous ethanol, 70% ethanol, and 1M HCl solution.

[0049] Using the waste residue from the production of rose essential oil in Example 1 as raw material, the flower residue powder was mixed with anhydrous ethanol at a material-to-liquid ratio of 1:50 g / mL, and extracted by ultrasonication (time 30 min, power 288 W, 80 ℃).

[0050] Using the waste residue from the production of rose essential oil in Example 1 as raw material, the flower residue powder was mixed with 70% ethanol at a material-to-liquid ratio of 1:50 g / mL and extracted by ultrasonication (time 30 min, power 288 W, 80 ℃).

[0051] Using the waste residue from the production of rose essential oil in Example 1 as raw material, the flower residue powder was mixed with 1M HCl solution at a material-to-liquid ratio of 1:50 g / mL and extracted by ultrasonication (time 30 min, power 288 W, 80 ℃).

[0052] like Figure 7 As shown, the extraction yield reached 23.02±0.98 mg / g of dried flower residue, which was significantly higher than that of traditional organic solvent extraction and acid extraction (Comparative Example 8).

[0053] Example 6 This invention further explores the effect of drying post-treatment on the ellagic acid content in rose petal residue from the perspective of flower residue processing technology.

[0054] The preparation method of flower residue is the same as in Example 1, except that the flower residue is subjected to natural drying and (60-140 ℃) drying treatment until constant weight. NADES is then prepared with choline chloride:urea = 1:2 molar ratio, with a uniform water addition of 30 wt%. After preparation, the flower residue powder and NADES are mixed at a material-to-liquid ratio of 1:50 g / mL, and extracted by ultrasonication (30 min, 288 W, 80 ℃).

[0055] The results showed that the ellagic acid content was lowest in the flower residue dried naturally at room temperature. The ellagic acid content exhibited a trend of first increasing and then decreasing within the temperature range of 60-140 ℃, reaching its highest extraction yield of 27.06±0.41 mg / g dried flower residue at 120 ℃. Figure 8 Without purification, the purity reached 60% (Figure 9), proving that this invention can achieve the green and efficient preparation of ellagic acid using NADES as a solvent. Meanwhile, the investigation of drying temperature showed that an appropriate drying temperature can effectively promote the re-release of ellagic acid, but excessively high temperatures may lead to its decomposition. This indicates the influence of drying temperature on the enrichment behavior of ellagic acid in rose pomace, providing a reference for industrial processing conditions.

[0056] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for efficiently preparing ellagic acid from rose processing by-products, characterized in that, Includes the following steps: (1) Fresh rose petals are used as raw materials, and essential oil is distilled by steam distillation. After distillation, the petal residue is dried and ground into powder to obtain rose petal residue. The drying conditions are 50-140 ℃. (2) Next, density functional theory calculations were performed using Guassian to theoretically analyze the interaction energy between ellagic acid and different natural eutectic solvents (NADES) and to screen suitable NADES solvents. (3) Prepare NADES solvent, add water to make the water content of NADES solvent 0-50 wt%, after preparation, mix rose pomace with NADES and perform ultrasonic extraction; NADES solvent is one of choline chloride-urea, choline chloride-lactic acid, or betaine-glycerol; The ratio of rose petal residue to NADES solution is 1:10-1:90 g / mL; The ultrasonic power is 0-480 W; the ultrasonic time is 0-60 min; and the ultrasonic temperature is 25-80 ℃.

2. The method according to claim 1, characterized in that, In step (1), the drying conditions are 120 °C.

3. The method according to claim 1, characterized in that, In step (3), the NADES solvent is choline chloride-urea.

4. The method according to claim 3, characterized in that, The molar ratio of choline chloride to urea is 2:1 to 1:

8.

5. The method according to claim 3, characterized in that, The molar ratio of choline chloride to urea is 1:

2.

6. The method according to claim 1, characterized in that, In step (3), water is added until the water content of the NADES solvent is 30 wt%.

7. The method according to claim 1, characterized in that, In step (3), the ratio of rose petal residue to NADES solution is 1:50 g / mL.

8. The method according to claim 1, characterized in that, In step (3), the ultrasonic power is 288 W.

9. The method according to claim 1, characterized in that, In step (3), the ultrasound time is 30 min.

10. The method according to claim 1, characterized in that, In step (3), the ultrasonic temperature is 80 ℃.

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