A high-nutrient-retention-rate medicinal and edible herbal plant extract and extraction method

Abstract

This invention relates to the field of plant extraction technology, and discloses a high-nutrient-retention rate extract from medicinal and edible herbal plants and its extraction method. It solves the problems of high loss of heat-sensitive nutrients and low extraction efficiency in existing processes. The method includes pretreatment, preparation of a compound extraction system, low-temperature segmented extraction, low-temperature solid-liquid separation, purification, freeze-drying, and testing and packaging. It utilizes an ethanol-propylene glycol composite solvent, nutrient protectants such as magnesium vitamin C phosphate, and a nitrogen-protected, low-temperature process throughout. The various indicators of this invention are significantly superior to traditional and original methods, improving nutrient retention and extraction efficiency. The process is scientifically sound, suitable for industrial applications, and can expand the high-end application scenarios of *Heliotropium indicum*.

Description

Technical Field

[0001] This invention relates to the field of plant extraction technology, specifically to an extract of medicinal and edible herbal plants with high nutrient retention rate and an extraction method thereof. Background Technology

[0002] Heart-saving grass is a medicinal and edible herb, mainly produced in Sichuan, Hubei, Shandong, Northeast my country, and other provinces. It is abundant and has a high yield, and is listed as a medicinal and edible plant by the Ministry of Health. Modern pharmacological studies have shown that heart-saving grass contains rich nutritional and active ingredients. Flavonoids can dilate blood vessels, promote blood circulation, and reduce myocardial oxygen consumption; alkaloids have hemostatic, antibacterial, and cardiac stimulant effects; and vitamin C can enhance antioxidant capacity and maintain normal metabolism. These components give it significant biological functions and application value in nourishing the heart and liver, lowering blood pressure and lipids, and preventing cardiovascular diseases, making it a medicinal and edible raw material with great development potential.

[0003] Currently, the application of *Heliotropium indicum* is mostly limited to inefficient methods such as stir-frying and brewing tea, with extremely low deep processing utilization, accounting for only about 5% of the total output. Furthermore, if not handled promptly after harvest, it is highly susceptible to spoilage and deterioration, resulting in severe post-harvest losses. Existing extraction methods for *Heliotropium indicum* extract mainly include traditional water extraction, alcohol extraction, and ultrasound-assisted extraction. However, these methods all have significant drawbacks: traditional water and alcohol extractions often employ high-temperature extraction processes, while components such as flavonoids and vitamin C are highly heat-sensitive and easily oxidize and degrade under high-temperature conditions, leading to extremely low nutrient retention. Although ultrasound-assisted extraction can shorten the extraction time, it requires significant equipment investment, process parameters are difficult to control, and there is no specific protection for heat-sensitive components, resulting in severe nutrient loss.

[0004] Furthermore, existing research on the deep processing of *Heliotropium indicum* primarily focuses on products such as enzymes and teas, with limited research on efficient extraction and retention methods specifically targeting its heat-sensitive nutrients. Moreover, no mature, scalable process has been developed. Therefore, addressing the problems of low retention rates of heat-sensitive nutrients, insufficient extraction efficiency, simple processes, common solvent systems, and inability to meet the demands of high-end applications in existing *Heliotropium indicum* extraction methods, it is of significant practical importance and application value to develop an advanced, industrially applicable extraction method that can precisely control extraction conditions, employ optimized composite solvents and dedicated protection strategies, significantly improve the retention rates of nutrients such as flavonoids, alkaloids, and vitamin C.

[0005] In view of this, the applicant conducted in-depth research on the above-mentioned issues, which led to this case. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a medicinal and edible herbal extract with high nutrient retention rate and an extraction method, thereby solving technical problems such as easy degradation of heat-sensitive nutrients, low retention rate, insufficient extraction efficiency, simple process, and common solvent system in existing extracts of *Heliotropium indicum*.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for extracting medicinal and edible herbs with high nutrient retention includes the following steps: S1. Raw material pretreatment: Select fresh tender stems and leaves of the heart-saving grass, remove impurities, residual roots and rotten parts, rinse and drain, freeze at -25~-20℃ for 18-24h, pulverize into 200-300 mesh powder at low temperature, vacuum dry, add compound antioxidant pretreatment agent and let stand to complete the pretreatment for use. S2. Preparation of the compound extraction system: Use a 50%-70% volume fraction ethanol-propylene glycol mixed solution as the extraction solvent, wherein the volume ratio of ethanol to propylene glycol is 3:1. Add 0.1-0.2 mol / L citrate-sodium dihydrogen phosphate buffer to adjust the pH value to 4.5-5.5, then add a nutrient protectant, stir evenly and refrigerate to obtain the compound buffer extract. S3. Low-temperature pH precise control extraction: The pretreated heart-saving grass powder and the compound buffer extract are mixed at a material-liquid ratio of 1:20-1:30, protected by nitrogen, and extracted in stages at 28-32℃ and 180-220r / min to obtain the extract. S4. Low-temperature solid-liquid separation: Centrifuge the extract at low temperature and high speed, collect the supernatant, repeat the extraction once with the precipitate and combine the supernatants, add a clarifying agent, refrigerate and stand, then centrifuge again to remove impurities. S5. Purification and refining: The crude extract is filtered through an organic filter membrane, ultrafiltered through a modified polyethersulfone ultrafiltration membrane, and then concentrated by nanofiltration to obtain a refined and concentrated extract; S6. Low-temperature vacuum freeze-drying: After pre-freezing the refined and concentrated extract, the temperature is raised in stages and the vacuum freeze-drying is carried out continuously with nitrogen protection to obtain the extract powder of the heart-saving grass. S7. Testing and Packaging: Test the extract components, and after passing the test, vacuum pack with nitrogen.

[0008] Furthermore, in step S1, the composite antioxidant pretreatment agent is composed of L-cysteine ​​and glutathione mixed in a mass ratio of 1:1, and the amount added is 0.5%-1.0% of the mass of the dried heart-saving grass powder; the low-temperature ultrafine grinding temperature does not exceed 8℃, and nitrogen protection is used; the vacuum drying conditions are 28-32℃, vacuum degree 0.07-0.09MPa, and drying time 3-4h.

[0009] Furthermore, the nutrient protectant is composed of magnesium vitamin C phosphate, β-cyclodextrin, and EDTA-2Na in a mass ratio of 2:3:1. Among them, magnesium vitamin C phosphate has a stability that is more than 80% higher than that of ordinary vitamin C, which can prevent oxidation and failure during the extraction process. The amount of nutrient protectant added is 0.3%-0.5% of the mass of the extraction solvent. The refrigeration temperature is 4-8℃ and the refrigeration time is 30 minutes.

[0010] Furthermore, in step S3, the nitrogen flow rate is 0.2-0.3 L / min; the segmented extraction method is as follows: first, extract by low-speed stirring for 1 h, then let stand at a constant temperature for 0.5 h, and repeat twice; the extraction temperature is 30℃, the pH value is 5.0, and the material-to-liquid ratio is 1:25.

[0011] Furthermore, in step S4, the centrifugation conditions are: rotation speed 4000-5000 r / min, temperature 2-6℃, centrifugation time 15-20 min; the clarifying agent is chitosan-pectin composite clarifying agent, the amount added is 0.2%-0.4% of the crude extract volume, the refrigeration temperature is 4℃, and the standing time is 2 h.

[0012] Furthermore, in step S5, the organic filter membrane has a pore size of 0.22 μm; the ultrafiltration membrane is made of modified polyethersulfone, with an ultrafiltration pressure of 0.15-0.25 MPa, an ultrafiltration temperature of 4-8℃, and a molecular weight cutoff of 3000-8000 Da; the nanofiltration concentration pressure is 0.3-0.4 MPa, the temperature is 4-8℃, and the concentration is reduced to 1 / 3-1 / 2 of the original volume.

[0013] Furthermore, in step S6, the pre-freezing temperature is -45 to -40℃, the pre-freezing time is 3 hours; the sublimation drying temperature is -35 to -30℃, the desorption drying temperature is 25 to 30℃, the vacuum degree is 0.095-0.1 MPa, and the drying time is 10-14 hours.

[0014] A medicinal and edible herbal extract with high nutrient retention rate is prepared by the extraction method described in any one of claims 1-7, wherein the extract contains flavonoids ≥2.8%, alkaloids ≥1.0%, vitamin C ≥0.4%, moisture content ≤4.0%, and DPPH scavenging rate ≥90%.

[0015] This invention provides a medicinal and edible herbal extract with high nutrient retention rate and an extraction method. It has the following beneficial effects: 1. This invention uses an ethanol-propylene glycol composite solvent instead of the traditional single ethanol solvent, balancing the dissolution of both fat-soluble and water-soluble nutrients while minimizing nutrient damage. Nutrient protectants provide comprehensive protection: β-cyclodextrin inclusion protection, EDTA-2Na chelation of metal ions, and vitamin C antioxidant effects reduce oxidative degradation of nutrients. Nitrogen protection is maintained throughout the extraction and drying process to completely isolate oxygen. Combined with ultra-low temperature freezing pretreatment and low-temperature pulverization, nutrient loss is minimized at the source. The extract of *Heliotropium indicum* prepared by this invention shows significantly improved retention rates of flavonoids, vitamin C, and alkaloids, superior to existing extraction techniques, demonstrating outstanding nutrient retention.

[0016] 2. The method of this invention has high extraction efficiency, and the nutrients are fully and specifically dissolved: Pretreatment using ultra-low temperature freezing at -25 to -20℃ followed by low-temperature ultrafine pulverization completely destroys the cell structure of *Heliotropium indicum*, increasing the contact area between the raw material and the extract. Combined with a composite buffer system for precise pH control, it promotes the targeted dissolution of target nutrients such as flavonoids, alkaloids, and vitamin C. The segmented extraction method avoids oxidation losses caused by prolonged stirring, while simultaneously improving extraction efficiency, achieving an extraction rate of over 95% for active ingredients such as flavonoids and alkaloids. 3. This invention optimizes the entire process of pretreatment, extraction, separation, concentration, and drying. It employs advanced technologies such as low-temperature high-speed centrifugation, modified ultrafiltration membrane ultrafiltration, and nanofiltration concentration to replace traditional simple separation methods, thereby improving the purity of the extract and reducing the loss of nutrients through adsorption. The entire process does not involve the addition of toxic or harmful reagents, meeting the high-end extraction requirements for medicinal and edible raw materials. The extract is highly safe, and all process parameters are easily controlled, resulting in low energy consumption and suitability for large-scale industrial production. Compared to the original method, the content of flavonoids, alkaloids, and vitamin C in the extract is significantly increased.

[0017] 4. The extract of *Heliotropium indicum* prepared by this invention has high content and strong stability of nutrients such as flavonoids, alkaloids, and vitamin C. After purification and refining, macromolecular impurities, colloidal substances, and ineffective components are removed, resulting in high purity, good fluidity, and significantly better antioxidant activity than existing extracts and the original extract. This fully utilizes the medicinal and health-preserving value of *Heliotropium indicum*, expands its application scope in high-end foods, functional health products, pharmaceutical preparations, and other fields, and enhances the added value of products.

[0018] 5. This invention addresses the problems of low utilization rate of deep processing of *Heliotropium indicum*, serious post-harvest losses, and low added value of products by providing an efficient and advanced extraction method. This method can transform *Heliotropium indicum* raw materials into highly nutritious and high-purity extract products, which not only improves the utilization rate of *Heliotropium indicum* resources but also enhances its industrial value, promotes its large-scale and high-value development, and has good economic and social benefits. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0020] A method for extracting medicinal and edible herbs with high nutrient retention includes the following steps: S1. Raw material pretreatment: Select fresh tender stems and leaves of *Heliotropium indicum*, remove impurities, residual roots and rotten parts, rinse twice quickly with deionized water, drain the surface water, and place in an ultra-low temperature freeze-drying environment of -22℃ for 21 hours. After removal, use a low-temperature ultra-micro pulverizer to grind *Heliotropium indicum* powder with a particle size of 250 mesh. During the pulverization process, control the temperature to not exceed 8℃ and purge with nitrogen for protection. Place the powder in a vacuum freeze-drying oven and dry it at 30℃ and a vacuum degree of 0.08MPa for 3.5 hours to remove moisture and obtain dried *Heliotropium indicum* powder. Add 0.8% of a composite antioxidant pretreatment agent by mass to the dried powder. The composite antioxidant pretreatment agent is composed of L-cysteine ​​and glutathione mixed in a mass ratio of 1:1. After stirring evenly, let it stand for 12 minutes to complete the pretreatment and set aside for later use. S2. Preparation of the composite extraction system: A 60% (v / v) ethanol-propylene glycol mixed solution was used as the extraction solvent, with a volume ratio of ethanol to propylene glycol of 3:1. 0.15 mol / L citrate-sodium dihydrogen phosphate buffer was added to the extraction solvent to adjust the pH of the extraction system to 5.0. At the same time, a nutrient protectant was added, which was a mixture of vitamin C phosphate magnesium, β-cyclodextrin, and EDTA-2Na in a mass ratio of 2:3:1. The amount of nutrient protectant added was 0.4% of the mass of the extraction solvent. After stirring evenly, the mixture was refrigerated at 6℃ for 30 min to obtain a stable composite buffer extract. S3. Low-temperature pH precise control extraction: The pretreated heart-saving grass powder obtained in step S1 is mixed with the composite buffer extract prepared in step S2 at a material-to-liquid ratio of 1:25 (g / mL), and placed in a constant temperature low-temperature reactor. Nitrogen gas is introduced for protection, with a nitrogen flow rate of 0.25 L / min. The extraction temperature is controlled at 30℃, and the stirring speed is 200 r / min. A segmented extraction method is adopted: first, low-speed stirring extraction is performed for 1 h, and then constant temperature standing is performed for 0.5 h. This process is repeated twice to obtain the extract. S4. Low-temperature solid-liquid separation: Place the extract obtained in step S3 in a low-temperature high-speed centrifuge and centrifuge at 4500 r / min and 4℃ for 18 min, and collect the supernatant; repeat the extraction once with the composite buffer extract prepared in step S2, under the same extraction conditions as in step S3, and collect the supernatant after centrifugation. Combine the two supernatants to obtain the crude extract; add 0.3% of the volume of the clarifying agent (chitosan-pectin composite clarifying agent) to the crude extract, refrigerate at 4℃ for 2 h, and centrifuge again to remove precipitate impurities; S5. Purification and Refining: The clarified crude extract is filtered through a 0.22μm organic filter membrane to remove suspended impurities and microorganisms. The filtered extract is then ultrafiltered through a modified polyethersulfone ultrafiltration membrane at a pressure of 0.2MPa and a temperature of 6℃, with a molecular weight cutoff of 5000Da, to remove macromolecular impurities, colloidal substances, and some ineffective components. After ultrafiltration, nanofiltration is used for concentration at a pressure of 0.35MPa and a temperature of 6℃, concentrating the extract to half its original volume to obtain a refined concentrated extract. S6. Low-temperature vacuum freeze-drying: The refined and concentrated extract obtained in step S5 is placed in a vacuum freeze dryer, pre-frozen to -42°C and kept for 3 hours, then the sublimation drying temperature is controlled at -32°C, the desorption drying temperature is controlled at 28°C, the vacuum degree is 0.098MPa, and the drying is carried out for 12 hours. Nitrogen gas is continuously introduced for protection during the drying process to obtain dried heart grass extract powder. S7. Testing and Packaging: The components of the heart-saving grass extract powder obtained in step S6 are tested. The test results are as follows: flavonoid content 3.0%, alkaloid content 1.1%, vitamin C content 0.45%, moisture content 3.5%, and DPPH removal rate 92%. After passing the test, the powder is vacuum-packed with nitrogen to obtain the finished product. Example 2

[0021] A method for extracting medicinal and edible herbs with high nutrient retention includes the following steps: S1. Raw material pretreatment: Select fresh tender stems and leaves of *Heliotropium indicum*, remove impurities, residual roots and rotten parts, rinse quickly three times with deionized water, drain the surface water, and place in an ultra-low temperature freeze-drying environment of -25℃ for 24 hours. After removal, use a low-temperature ultra-micro pulverizer to grind *Heliotropium indicum* powder with a particle size of 200 mesh. During the pulverization process, control the temperature to not exceed 8℃ and purge with nitrogen for protection. Place the powder in a vacuum freeze-drying oven and dry it at 28℃ and a vacuum degree of 0.07MPa for 4 hours to remove moisture and obtain dried *Heliotropium indicum* powder. Add 0.5% of a composite antioxidant pretreatment agent by mass to the dried powder. The composite antioxidant pretreatment agent is composed of L-cysteine ​​and glutathione mixed in a mass ratio of 1:1. After stirring evenly, let it stand for 10 minutes to complete the pretreatment and set aside for later use. S2. Preparation of the composite extraction system: A 50% (v / v) ethanol-propylene glycol mixed solution was used as the extraction solvent, with a volume ratio of ethanol to propylene glycol of 3:1. 0.1 mol / L citrate-sodium dihydrogen phosphate buffer was added to the extraction solvent to adjust the pH of the extraction system to 4.5. At the same time, a nutrient protectant was added, which was a mixture of vitamin C phosphate magnesium, β-cyclodextrin, and EDTA-2Na in a mass ratio of 2:3:1. The amount of nutrient protectant added was 0.3% of the mass of the extraction solvent. After stirring evenly, the mixture was refrigerated at 4℃ for 30 min to obtain a stable composite buffer extract. S3. Low-temperature pH precise control extraction: The pretreated heart-saving grass powder obtained in step S1 is mixed with the composite buffer extract prepared in step S2 at a material-to-liquid ratio of 1:20 (g / mL), and placed in a constant temperature low-temperature reactor. Nitrogen gas is introduced for protection, with a nitrogen flow rate of 0.2 L / min. The extraction temperature is controlled at 28℃, and the stirring speed is 180 r / min. A segmented extraction method is adopted: first, low-speed stirring extraction is performed for 1 h, and then constant temperature standing is performed for 0.5 h. This process is repeated twice to obtain the extract. S4. Low-temperature solid-liquid separation: Place the extract obtained in step S3 in a low-temperature high-speed centrifuge and centrifuge at 4000 r / min and 2℃ for 20 min, and collect the supernatant; repeat the extraction once with the composite buffer extract prepared in step S2, under the same extraction conditions as in step S3, and collect the supernatant after centrifugation. Combine the two supernatants to obtain the crude extract; add 0.2% of the volume of the clarifying agent (chitosan-pectin composite clarifying agent) to the crude extract, refrigerate at 4℃ for 2 h, and centrifuge again to remove precipitate impurities; S5. Purification and Refining: The clarified crude extract is filtered through a 0.22μm organic filter membrane to remove suspended impurities and microorganisms. The filtered extract is then ultrafiltered through a modified polyethersulfone ultrafiltration membrane at a pressure of 0.15MPa and a temperature of 4℃, with a molecular weight cutoff of 3000Da, to remove macromolecular impurities, colloidal substances, and some ineffective components. After ultrafiltration, nanofiltration is used for concentration at a pressure of 0.3MPa and a temperature of 4℃, concentrating the extract to 1 / 3 of its original volume to obtain a refined and concentrated extract. S6. Low-temperature vacuum freeze-drying: The purified and concentrated extract obtained in step S5 is placed in a vacuum freeze dryer, pre-frozen to -45°C and kept for 3 hours, then the sublimation drying temperature is controlled at -35°C, the desorption drying temperature is controlled at 25°C, the vacuum degree is 0.095MPa, and the drying is carried out for 14 hours. Nitrogen gas is continuously introduced for protection during the drying process to obtain dried heart grass extract powder. S7. Testing and Packaging: The components of the heart-saving grass extract powder obtained in step S6 are tested. The test results are as follows: flavonoid content 2.8%, alkaloid content 1.0%, vitamin C content 0.4%, moisture content 3.9%, and DPPH removal rate 90%. After passing the test, the powder is vacuum-packed with nitrogen to obtain the finished product. Example 3

[0022] A method for extracting medicinal and edible herbs with high nutrient retention includes the following steps: S1. Raw material pretreatment: Select fresh tender stems and leaves of *Heliotropium indicum*, remove impurities, residual roots and rotten parts, rinse twice quickly with deionized water, drain the surface water, and place in -20℃ ultra-low temperature freezing for 18 hours. After taking it out, use a low-temperature ultra-micro pulverizer to grind it into *Heliotropium indicum* powder with a particle size of 300 mesh. During the pulverization process, control the temperature not to exceed 8℃ and introduce nitrogen for protection. Place the powder in a vacuum freeze-drying oven and dry it for 3 hours at 32℃ and a vacuum degree of 0.09MPa to remove moisture and obtain dried *Heliotropium indicum* powder. Add 1.0% of the mass of a composite antioxidant pretreatment agent to the dried powder. The composite antioxidant pretreatment agent is composed of L-cysteine ​​and glutathione mixed in a mass ratio of 1:1. After stirring evenly, let it stand for 15 minutes to complete the pretreatment and set aside for later use. S2. Preparation of the composite extraction system: A 70% (v / v) ethanol-propylene glycol mixed solution was used as the extraction solvent, with a volume ratio of ethanol to propylene glycol of 3:1. 0.2 mol / L citrate-sodium dihydrogen phosphate buffer was added to the extraction solvent to adjust the pH of the extraction system to 5.5. At the same time, a nutrient protectant was added, which was a mixture of vitamin C phosphate magnesium, β-cyclodextrin, and EDTA-2Na in a mass ratio of 2:3:1. The amount of nutrient protectant added was 0.5% of the mass of the extraction solvent. After stirring evenly, the mixture was refrigerated at 8℃ for 30 min to obtain a stable composite buffer extract. S3. Low-temperature pH precise control extraction: The pretreated heart-saving grass powder obtained in step S1 is mixed with the composite buffer extract prepared in step S2 at a material-to-liquid ratio of 1:30 (g / mL), and placed in a constant temperature low-temperature reactor. Nitrogen gas is introduced for protection, with a nitrogen flow rate of 0.3 L / min. The extraction temperature is controlled at 32℃, and the stirring speed is 220 r / min. A segmented extraction method is adopted: first, low-speed stirring extraction is performed for 1 h, and then constant temperature standing is performed for 0.5 h. This process is repeated twice to obtain the extract. S4. Low-temperature solid-liquid separation: Place the extract obtained in step S3 in a low-temperature high-speed centrifuge and centrifuge at 5000 r / min and 6℃ for 15 min, and collect the supernatant; repeat the extraction once with the composite buffer extract prepared in step S2, under the same extraction conditions as in step S3, and collect the supernatant after centrifugation. Combine the two supernatants to obtain the crude extract; add 0.4% of the volume of the clarifying agent (chitosan-pectin composite clarifying agent) to the crude extract, refrigerate at 4℃ for 2 h, and centrifuge again to remove precipitate impurities; S5. Purification and Refining: The clarified crude extract is filtered through a 0.22μm organic filter membrane to remove suspended impurities and microorganisms. The filtered extract is then ultrafiltered through a modified polyethersulfone ultrafiltration membrane at a pressure of 0.25MPa and a temperature of 8℃, with a molecular weight cutoff of 8000Da, to remove macromolecular impurities, colloidal substances, and some ineffective components. After ultrafiltration, nanofiltration is used for concentration at a pressure of 0.4MPa and a temperature of 8℃, concentrating the extract to half its original volume to obtain a refined concentrated extract. S6. Low-temperature vacuum freeze-drying: The purified and concentrated extract obtained in step S5 is placed in a vacuum freeze dryer, pre-frozen to -40°C and kept for 3 hours, then the sublimation drying temperature is controlled at -30°C, the desorption drying temperature is controlled at 30°C, the vacuum degree is 0.1MPa, and the drying is carried out for 10 hours. Nitrogen gas is continuously introduced for protection during the drying process to obtain dried heart grass extract powder. S7. Testing and Packaging: The components of the heart-saving grass extract powder obtained in step S6 are tested. The test results are as follows: flavonoid content 3.2%, alkaloid content 1.2%, vitamin C content 0.5%, moisture content 3.2%, and DPPH removal rate 94%. After passing the test, the powder is vacuum-packed with nitrogen to obtain the finished product.

[0023] Comparative Example 1 The traditional high-temperature water extraction method includes the following steps: S1. Raw material pretreatment: Take 100g of dried Gynostemma pentaphyllum powder, no ultra-low temperature freezing or antioxidant pretreatment is required, and it can be used directly; S2. Extraction system: Deionized water is used as the extraction solvent, the material-to-liquid ratio is 1:20 (g / mL), the pH value is not adjusted, and no nutrient protectant is added; S3. Extraction conditions: Place in a conventional reaction vessel, extract at 90℃ with stirring for 2 hours, stirring speed 180r / min, without nitrogen protection, and without segmented extraction; S4. Solid-liquid separation: Centrifuge at 3500 r / min at room temperature for 12 min, collect the supernatant, and the precipitate does not need to be extracted again; S5. Purification and refining: Suspended impurities are removed by filtration through a 0.45μm organic filter membrane only, without ultrafiltration or nanofiltration concentration steps; S6. Drying: Conventional vacuum drying was used at a temperature of 60℃ and a vacuum degree of 0.08MPa until constant weight was obtained to obtain extract powder. S7. Testing and Packaging: Test relevant indicators according to unified testing standards, and prepare for use.

[0024] Comparative Example 2 S1. Raw material pretreatment: Take 100g of dry-based heart-saving grass powder, freeze at -18℃ for 18h, ultrafine grind into 150 mesh powder, vacuum dry at 32℃ and vacuum degree 0.07MPa for 2.5h, without adding composite antioxidant pretreatment agent; S2. Extraction system: 50% ethanol was used as the extraction solvent, the solid-liquid ratio was 1:20 (g / mL), 0.08 mol / L citrate-sodium citrate buffer was added to adjust the pH to 5.0, only 0.2% vitamin C was added as a protective agent, and there was no refrigeration stabilization step. S3. Extraction conditions: 30℃, 180r / min stirring extraction for 3h, without nitrogen protection, without segmented extraction; S4. Solid-liquid separation: Centrifuge at 3500 r / min and 6℃ for 12 min, collect the supernatant, and extract the precipitate once more using the same extraction system. Combine the supernatants without any clarifying agent treatment. S5. Purification and refining: Filtration with a 0.45μm organic filter membrane, followed by ultrafiltration with a common polyethersulfone ultrafiltration membrane, and then direct drying after ultrafiltration; S6. Drying: Vacuum freeze drying, pre-freeze at -40℃ for 2 hours, sublimation drying temperature at -38℃, vacuum degree 0.095MPa, drying for 10 hours, without nitrogen protection; S7. Testing and Packaging: Test relevant indicators according to unified testing standards, and prepare for use.

[0025] After the above experiments were completed, the following detection methods were used uniformly to perform parallel detections of the same index three times, and the average value was taken as the final result to ensure data reliability: High-performance liquid chromatography (HPLC) was used to detect flavonoid content, referring to GB / T20574-2006 "Determination of Flavonoid Content in Propolis". The mobile phase was methanol-0.1% phosphoric acid solution, volume ratio 50:50, detection wavelength 254 nm, flow rate 1.0 mL / min, column temperature 30℃; Alkaloid content was detected using the acidic dye colorimetric method, referring to the 2020 edition of the Chinese Pharmacopoeia, Part I, with sedumine as the reference standard, detection wavelength 410 nm; Vitamin C content was detected using the iodometric method, referring to GB 5009.86-2016 The determination of ascorbic acid in food involved titration with iodine standard solution to calculate vitamin C content. The extraction rate was calculated using the formula: Extraction rate = (Total mass of target components in the extract ÷ Total mass of target components in the raw material of *Heliotropium indicum*) × 100%, where the target components were the total mixture of flavonoids and alkaloids, based on the dry basis of *Heliotropium indicum* raw material. The DPPH· scavenging rate was detected using ultraviolet-visible spectrophotometry, referring to GB / T 31740.2-2015 Tea Products Part 2: Tea Polyphenols, with a detection wavelength of 517 nm. The DPPH· scavenging rate reflected the antioxidant activity of the extract. The moisture content was determined using vacuum drying, referring to GB 5009.3-2016 Determination of Moisture in Food, and calculated after drying to constant weight.

[0026] The comparison test results are shown in the table below:

[0027] Based on the above testing data and process differences analysis, the following core conclusions can be drawn: Comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that the optimized extraction process of the present invention can significantly improve the retention rate of the core nutrients of *Heliotropium indicum*, namely flavonoids, alkaloids and vitamin C. The improvement rate is more than 55% compared with Comparative Example 1 and between 22% and 43% compared with Comparative Example 2. This solves the core technical problem of easy degradation and low retention rate of heat-sensitive nutrients in the prior art.

[0028] Comparative Examples 1-3 show that appropriately increasing the concentration of the extraction solvent, the material-to-liquid ratio, and the ultrafiltration pressure can promote the dissolution of flavonoids and reduce adsorption losses. The core reason is that Comparative Example 1 uses high-temperature water extraction at 90℃ without any protective measures, making flavonoids easily oxidized and degraded; Comparative Example 2 uses a single ethanol solvent, with only ordinary vitamin C added for protection, and no nitrogen protection, resulting in significant flavonoid loss; while the embodiments of this invention use an ethanol-propylene glycol composite solvent, combined with vitamin C magnesium phosphate, β-cyclodextrin inclusion, EDTA-2Na chelation of metal ions, and nitrogen protection throughout the process, reducing flavonoid oxidation from the source. At the same time, ultra-low temperature freezing and low-temperature ultra-fine pulverization promote the full dissolution of flavonoids. Furthermore, this invention significantly promotes the dissolution and retention of alkaloids. Although alkaloids are slightly less heat-sensitive than flavonoids and vitamin C, high temperatures and pH imbalances can still lead to structural damage. The high-temperature extraction in Comparative Example 1 and the unstable pH buffer system in Comparative Example 2 both resulted in alkaloid loss. This invention uses a citrate-sodium dihydrogen phosphate buffer to precisely maintain a stable pH range of 4.5-5.5, preventing alkaloid hydrolysis. Simultaneously, the composite solvent synergistically promotes dissolution, and nitrogen protection reduces oxidation loss. In addition, vitamin C is the most heat-sensitive component. In Comparative Example 1, almost half of the vitamin C was oxidized during high-temperature extraction. Comparative Example 2 used ordinary vitamin C as a protective agent, which has poor stability and is prone to failure during extraction. This invention uses magnesium vitamin C phosphate, combined with a composite antioxidant pretreatment agent, continuous nitrogen protection, and a low-temperature process to minimize vitamin C oxidation and significantly improve retention.

[0029] The extraction efficiency of this invention is as high as 93.80%-96.50%, which is more than 37% higher than that of Comparative Example 1 and 3%-4% higher than that of Comparative Example 2. Through optimization measures such as ultra-low temperature freezing to break cell walls, synergistic dissolution with composite solvents, and segmented extraction, the target nutrients are fully dissolved, balancing extraction efficiency and nutrient retention rate, making it suitable for large-scale industrial production. Comparative Example 1 uses a single water solvent. Although high-temperature extraction can partially break cell walls, the loss of nutrients is severe due to oxidation, and water has poor solubility for fat-soluble flavonoids, resulting in a low extraction rate. Comparative Example 2 uses a single ethanol solvent, which does not sufficiently break cell walls and lacks a segmented extraction process, resulting in insufficient dissolution of components. This invention uses ultra-low temperature freezing at -25 to -20°C to break cell walls and then uses 200-300 mesh low-temperature ultrafine pulverization, combined with segmented extraction with an ethanol-propylene glycol composite solvent, which significantly improves extraction efficiency while reducing nutrient loss, achieving a dual improvement in extraction rate and retention rate.

[0030] The *Heliotropium indicum* extract prepared in this invention exhibits a DPPH· scavenging rate of 90.00%-94.00%, significantly superior antioxidant activity compared to Comparative Examples 1 and 2. Its moisture content is controlled at 3.20%-3.90%, meeting stability requirements. Furthermore, the extract demonstrates high purity, good flowability, and absence of significant impurities, making it suitable for wide application in high-end foods, functional health products, and pharmaceutical preparations, thereby significantly increasing product added value. Comparative Example 1 suffers from severe nutrient loss, low antioxidant content, and weak antioxidant activity. While Comparative Example 2 reduces some nutrient loss, its antioxidant retention rate is still lower than that of the embodiments of this invention. The embodiments of this invention, through multiple protection strategies, maximize the retention of antioxidant components such as flavonoids and vitamin C. The purification process removes ineffective impurities, further enhancing antioxidant activity and laying the foundation for high-end applications of the extract.

[0031] Compared to the comparative examples, the moisture content of Example 1 was lower than that of Comparative Examples 1 and 2. Comparative Example 1 used conventional vacuum drying; although high-temperature drying can remove moisture, it easily leads to the oxidation of nutrients, and the moisture control precision is low. Comparative Example 2 used vacuum freeze-drying, but it lacked a segmented heating mode and nitrogen protection, resulting in poor drying uniformity and a higher moisture content. This invention uses segmented heating vacuum freeze-drying, with pre-freezing, sublimation drying, and desorption drying performed step by step, combined with nitrogen protection throughout the process. This not only thoroughly removes moisture but also avoids the oxidation of nutrients during drying, while ensuring that the extract powder is uniform, free of lumps, and improving stability.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for extracting medicinal and edible herbal plants with high nutrient retention rate, characterized in that, Includes the following steps: S1. Raw material pretreatment: Select fresh tender stems and leaves of the heart-saving grass, remove impurities, residual roots and rotten parts, rinse and drain, freeze at -25~-20℃ for 18-24h, pulverize into 200-300 mesh powder at low temperature, vacuum dry, add compound antioxidant pretreatment agent and let stand to complete the pretreatment for use. S2. Preparation of the compound extraction system: Use a 50%-70% volume fraction ethanol-propylene glycol mixed solution as the extraction solvent, wherein the volume ratio of ethanol to propylene glycol is 3:

1. Add 0.1-0.2 mol / L citrate-sodium dihydrogen phosphate buffer to adjust the pH value to 4.5-5.5, then add a nutrient protectant, stir evenly and refrigerate to obtain the compound buffer extract. S3. Low-temperature pH precise control extraction: The pretreated heart-saving grass powder and the compound buffer extract are mixed at a material-liquid ratio of 1:20-1:30, protected by nitrogen, and extracted in stages at 28-32℃ and 180-220r / min to obtain the extract. S4. Low-temperature solid-liquid separation: Centrifuge the extract at low temperature and high speed, collect the supernatant, repeat the extraction once with the precipitate and combine the supernatants, add a clarifying agent, refrigerate and stand, then centrifuge again to remove impurities. S5. Purification and refining: The crude extract is filtered through an organic filter membrane, ultrafiltered through a modified polyethersulfone ultrafiltration membrane, and then concentrated by nanofiltration to obtain a refined and concentrated extract. S6. Low-temperature vacuum freeze-drying: After pre-freezing the refined and concentrated extract, the temperature is raised in stages and the vacuum freeze-drying is carried out continuously with nitrogen protection to obtain the extract powder of the heart-saving grass. S7. Testing and Packaging: Test the extract components, and after passing the test, vacuum pack with nitrogen.

2. The method for extracting medicinal and edible herbal plants with high nutrient retention rate according to claim 1, characterized in that, In step S1, the composite antioxidant pretreatment agent is composed of L-cysteine ​​and glutathione mixed in a mass ratio of 1:1, and the amount added is 0.5%-1.0% of the mass of dried heart-saving grass powder; the low-temperature ultrafine grinding temperature does not exceed 8℃, and nitrogen protection is used; the vacuum drying conditions are 28-32℃, vacuum degree 0.07-0.09MPa, and drying time 3-4h.

3. The method for extracting medicinal and edible herbal plants with high nutrient retention rate according to claim 1, characterized in that, The nutrient protectant is composed of magnesium vitamin C phosphate, β-cyclodextrin, and EDTA-2Na in a mass ratio of 2:3:

1. Among them, magnesium vitamin C phosphate has a stability that is more than 80% higher than that of ordinary vitamin C, which can prevent oxidation and failure during the extraction process. The amount of nutrient protectant added is 0.3%-0.5% of the mass of the extraction solvent. The refrigeration temperature is 4-8℃ and the refrigeration time is 30 minutes.

4. The method for extracting medicinal and edible herbal plants with high nutrient retention rate according to claim 1, characterized in that, In step S3, the nitrogen flow rate is 0.2-0.3 L / min; the segmented extraction method is as follows: first, extract by low-speed stirring for 1 h, then let stand at a constant temperature for 0.5 h, and repeat twice; the extraction temperature is 30℃, the pH value is 5.0, and the material-to-liquid ratio is 1:

25.

5. The method for extracting medicinal and edible herbal plants with high nutrient retention rate according to claim 1, characterized in that, In step S4, the centrifugation conditions are: rotation speed 4000-5000 r / min, temperature 2-6℃, centrifugation time 15-20 min; the clarifying agent is chitosan-pectin composite clarifying agent, the amount added is 0.2%-0.4% of the crude extract volume, the refrigeration temperature is 4℃, and the standing time is 2 h.

6. The method for extracting medicinal and edible herbal plants with high nutrient retention rate according to claim 1, characterized in that, In step S5, the organic filter membrane has a pore size of 0.22 μm; the ultrafiltration membrane is made of modified polyethersulfone, with an ultrafiltration pressure of 0.15-0.25 MPa, an ultrafiltration temperature of 4-8℃, and a molecular weight cutoff of 3000-8000 Da; the nanofiltration concentration pressure is 0.3-0.4 MPa, the temperature is 4-8℃, and the concentration is reduced to 1 / 3-1 / 2 of the original volume.

7. The method for extracting medicinal and edible herbal plants with high nutrient retention rate according to claim 1, characterized in that, In step S6, the pre-freezing temperature is -45 to -40℃, the pre-freezing time is 3 hours; the sublimation drying temperature is -35 to -30℃, the desorption drying temperature is 25 to 30℃, the vacuum degree is 0.095-0.1MPa, and the drying time is 10-14 hours.

8. An extract from a medicinal and edible herbal plant, characterized in that, The extract is prepared by any one of the extraction methods described in claims 1-7, and the extract contains flavonoids ≥2.8%, alkaloids ≥1.0%, vitamin C ≥0.4%, moisture ≤4.0%, and DPPH· scavenging rate ≥90%.

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