An indigo blue oral colon release preparation, its preparation method and application

Abstract

The application discloses a blue vitriol oral colon release preparation, a preparation method and application thereof, and belongs to the technical field of medicines, and comprises a blue vitriol granule core, an isolation layer and a colon positioning coating layer; the isolation layer is completely coated on the surface of the blue vitriol granule core; the colon positioning coating layer is coated on the surface of the isolation layer; and the administration mode of the preparation is: releasing through oral administration directly to the colon. The application adopts the above-mentioned blue vitriol oral colon release preparation, the preparation method and application thereof, and solves key problems such as coating defects, drug degradation and insufficient release precision in the colon target delivery of the blue vitriol through a trinity technical scheme of a complete isolation layer, critical colon coating weight increase and a fluidized bed bottom spraying process, so that the active ingredients of the blue vitriol can act on the lesion site in the colon environment in an integrated chemical form and with sufficient dosage, and high-efficiency, safe and stable ulcerative colitis treatment effects are achieved.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical technology, and in particular to an oral colon-release formulation of indigo naturalis, its preparation method, and its application. Background Technology

[0002] Ulcerative colitis (UC) is a chronic, nonspecific inflammatory bowel disease affecting the colorectal mucosa. Its clinical manifestations include diarrhea, rectal bleeding, abdominal pain, and tenesmus. The disease course is protracted and recurrent, severely impacting patients' quality of life. In recent years, the incidence of UC in my country has been on a continuous upward trend, becoming one of the most common digestive system diseases. Currently, drug treatment for UC mainly includes aminosalicylic acids, glucocorticoids, immunosuppressants, and biologics. However, these drugs generally suffer from high relapse rates after discontinuation, significant toxic side effects with long-term use, and poor response in some patients. Since the lesions in UC are mainly concentrated in the colonic mucosa, a drug delivery strategy that directly delivers drugs to the lesion site in the colon to achieve high local concentrations and low systemic exposure is an important direction for improving efficacy and reducing side effects.

[0003] Indigo naturalis is a traditional Chinese medicine derived from the dried powder obtained by processing the leaves or stems of plants such as *Strobilanthes cusia* (Acanthaceae), *Polygonum tinctorium* (Polygonaceae), or *Isatis tinctoria* (Brassicaceae). It possesses properties such as clearing heat and detoxifying, cooling the blood, and reducing blemishes. Modern pharmacological studies have shown that components in indigo naturalis, such as indigofera tinctoria, indirubin, and tryptophan, have clear anti-inflammatory and mucosal repair effects on ulcerative colitis. Its mechanism of action involves inhibiting the NF-κB pathway, regulating intestinal immunity, and repairing the intestinal epithelial barrier.

[0004] However, after oral administration, the active ingredients of indigo have poor solubility and low absorption rate. Ordinary powders or tablets are released in large quantities in the stomach and small intestine. By the time the drug reaches the lesion site in the colon, the concentration has been significantly reduced, resulting in poor efficacy and the need for large doses, which increases the potential systemic toxic side effects. Summary of the Invention

[0005] The purpose of this invention is to provide an oral colon-release formulation of indigo naturalis, its preparation method, and its application. Through a three-in-one technical solution of complete isolation layer, critical colon coating weight gain, and fluidized bed bottom spraying process, the key problems of coating defects, drug degradation, and insufficient release precision in colon-targeted delivery of indigo naturalis are solved from the source of formulation. This enables the active ingredient of indigo naturalis to act on the lesion site in its complete chemical form, in the colonic environment, and at a sufficient dose, achieving a highly efficient, safe, and stable therapeutic effect for ulcerative colitis.

[0006] To achieve the above objectives, the present invention provides an oral colon-release formulation of indigo naturalis, comprising an indigo naturalis granule core, an isolation layer, and a colon-targeting coating layer. The isolation layer completely covers the surface of the indigo naturalis granule core, and the colon-targeting coating layer covers the surface of the isolation layer. The administration method of the formulation is: release directly into the colon via oral administration.

[0007] Preferably, the indigo granule core is composed of 2-4 parts by weight of indigo fine powder, 3-6 parts by weight of microcrystalline cellulose and 0.4-0.8 parts by weight of povidone K30; the isolation layer is composed of 1-2 parts by weight of hydroxypropyl methylcellulose E5 and 0.2-0.4 parts by weight of polyethylene glycol 6000; the colon-positioning coating layer is composed of 1-3 parts by weight of Eudragit S100, 0.2-0.5 parts by weight of triethyl citrate and 0.3-0.6 parts by weight of talc.

[0008] Preferably, the indigo granule core is composed of 2 parts by weight of indigo fine powder, 3 parts by weight of microcrystalline cellulose and 0.5 parts by weight of povidone K30; the isolation layer is composed of 1 part by weight of hydroxypropyl methylcellulose E5 and 0.2 parts by weight of polyethylene glycol 6000; the colon positioning coating layer is composed of 1.2 parts by weight of Eudragit S100, 0.24 parts by weight of triethyl citrate and 0.3 parts by weight of talc.

[0009] Preferably, the weight gain of the colon-positioning coating layer is 10-12% of the total weight of the isolation layer and the indigo granule core, and the weight gain of the isolation layer is 8-12% of the weight of the indigo granule core.

[0010] The preparation method of the above-described oral colon-release formulation of indigo naturalis includes the following steps: S1. Preparation of Indigo Particle Core: Indigo fine powder and microcrystalline cellulose are mixed evenly, and a 70% ethanol solution of povidone K30 is added to make a soft material. The soft material is sieved and granulated, dried and sized to obtain Indigo Particle Core. S2. Coating the Indigo Particle Core with an Isolation Layer: The Indigo Particle Core prepared in S1 is placed in a fluidized bed and coated with a 70% ethanol solution of hydroxypropyl methylcellulose E5 and polyethylene glycol 6000 by bottom spraying, so that the isolation layer completely covers the surface of the Indigo Particle Core until the weight gain is 8-12%. After drying, the isolation layer coated particles are obtained. S3. Eudragit S100, triethyl citrate, and talc are dissolved in 70% ethanol to prepare a bottom spray solution. The bottom spray solution is used to bottom spray coat the isolation layer coated particles obtained in S2 in a fluidized bed. The coating weight increases to 10-12% of the isolation layer coated particles. After drying, the formulation is obtained.

[0011] Preferably, in S1, the concentration of povidone K30 is 5-8%, the sieve opening is 18 mesh, the drying temperature is 60-70℃, the drying time is 1-2h, and the granules are passed through a 20 mesh sieve.

[0012] Preferably, in S2, the fluidized bed process parameters are: inlet air temperature 55-65℃, outlet air temperature 40-48℃, material temperature 35-40℃, spraying speed 2-3mL / min, atomization pressure 0.2-0.3MPa; and drying time 20-30min.

[0013] Preferably, in S3, the process parameters are: inlet air temperature 60-70℃, outlet air temperature 45-50℃, material temperature 38-42℃, spraying speed 2-3mL / min, and atomization pressure 0.25-0.35MPa.

[0014] Preferably, in S3, the drying temperature is 55-65℃, the drying time is 1-1.5h, and the granules are passed through a 20-mesh sieve.

[0015] The above-described oral colon-release formulation of indigo naturalis is used in the preparation of drugs for treating or improving ulcerative colitis.

[0016] Therefore, the present invention, by employing the above-mentioned oral colon-release formulation of indigo naturalis, its preparation method, and its application, has the following beneficial effects: An isolation layer composed of hydroxypropyl methylcellulose (HMC) E5 and polyethylene glycol 6000 is placed between the indigo granule core and the Eudragit S100 colon coating layer. HMC E5 exhibits excellent film-forming properties, forming a continuous and dense film on the granule surface. Polyethylene glycol 6000 acts as a plasticizer, intercalating between the HMC molecular chains to lower the glass transition temperature of the film, imparting sufficient flexibility and preventing microcracks from forming during fluidized bed airflow impact, drying shrinkage, and subsequent granulation. After the isolation layer completely coats the indigo granule core, it blocks direct contact between the hydrophobic groups on the indigo surface and the carboxyl groups of Eudragit S100, avoiding degradation pathways such as decreased coating adhesion, pinhole formation, and adsorption or formation of conjugates due to interfacial property mismatch. Furthermore, the hydroxyl groups in the isolation layer can form hydrogen bonds with the carboxyl groups in the subsequent Eudragit S100 coating layer, improving interlayer bonding and making the double coating a unified whole, further enhancing the mechanical strength and gastric acid barrier capacity of the coating layer.

[0017] Fluidized bed bottom spray coating keeps the particles in a suspended fluidized state, ensuring that each particle surface is uniformly contacted by atomized droplets. The droplets then rapidly dry on the particle surface to form a film, preventing particle adhesion and inconsistent coating thickness. Especially for small-sized, low-density indigo particles, the airflow dynamics of the fluidized bed ensure that the particles circulate within the coating zone. In each cycle, the particles are coated with an extremely thin layer of coating liquid as they pass over the area above the nozzle. Through multiple cycles, this accumulates to form a uniformly thick and dense coating film.

[0018] When the weight gain is less than 10%, the coating layer is too thin to resist H in gastric juice. + Erosion caused by factors such as ionic strength and pepsin, trace amounts of water molecules and H+ +Drug release can occur prematurely by diffusing through the submicroscopic pores in the coating layer to the particle core. However, when the weight gain exceeds 12%, the coating layer becomes too thick. In a colonic environment with a pH ≥ 7.0, the dissociation of carboxyl groups on the Eudragit S100 molecular chain and the swelling and dissolution of the polymer require a longer time, resulting in significantly delayed drug release and an inability to rapidly establish an effective therapeutic concentration at the site of colonic lesions. A narrow window of only 10%-12% ensures that the coating layer thickness is precisely at the critical state of completely blocking gastric acid penetration while simultaneously allowing for rapid and complete dissolution in the colonic environment, thus simultaneously meeting the dual requirements of no release in the upper gastrointestinal tract and rapid release in the colon.

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a graph showing the release rate test results of an oral colon-release formulation of indigo naturalis according to the present invention, its preparation method, and application examples 1-5 and comparative examples 1-10; Figure 2 The figures show the test results of the modeling experiments of the oral colon-release formulation of indigo naturalis, its preparation method and application examples 1-5 and comparative examples 1-10 of this invention; Figure 3 This is a graph showing the results of the oral colon-release formulation of indigo naturalis, its preparation method, and application examples 1-5 and comparative examples 1-10, including the levels of inflammatory factors and indigo content in the colon tissues of mice in each group. Detailed Implementation

[0021] This invention provides an oral colon-release formulation of indigo naturalis, comprising an indigo naturalis granule core, an isolation layer, and a colon-targeting coating layer. The isolation layer completely covers the surface of the indigo naturalis granule core, and the colon-targeting coating layer covers the surface of the isolation layer. The formulation is administered orally to release the indigo naturalis directly into the colon.

[0022] In this invention, the indigo granule core is composed of 2-4 parts by weight of indigo fine powder, 3-6 parts by weight of microcrystalline cellulose and 0.4-0.8 parts by weight of povidone K30; the isolation layer is composed of 1-2 parts by weight of hydroxypropyl methylcellulose E5 and 0.2-0.4 parts by weight of polyethylene glycol 6000; the colon positioning coating layer is composed of 1-3 parts by weight of Eudragit S100, 0.2-0.5 parts by weight of triethyl citrate and 0.3-0.6 parts by weight of talc.

[0023] In this invention, the indigo granule core is composed of 2 parts by weight of indigo fine powder, 3 parts by weight of microcrystalline cellulose and 0.5 parts by weight of povidone K30; the isolation layer is composed of 1 part by weight of hydroxypropyl methylcellulose E5 and 0.2 parts by weight of polyethylene glycol 6000; the colon positioning coating layer is composed of 1.2 parts by weight of Eudragit S100, 0.24 parts by weight of triethyl citrate and 0.3 parts by weight of talc.

[0024] In this invention, the weight gain of the colon positioning coating layer is 10-12% of the total weight of the isolation layer and the indigo granule core, and the weight gain of the isolation layer is 8-12% of the weight of the indigo granule core.

[0025] The preparation method of the above-described oral colon-release formulation of indigo naturalis includes the following steps: S1. Preparation of Indigo Particle Core: Indigo fine powder and microcrystalline cellulose are mixed evenly, and a 70% ethanol solution of povidone K30 is added to make a soft material. The soft material is sieved and granulated, dried and sized to obtain Indigo Particle Core. S2. Coating the Indigo Particle Core with an Isolation Layer: The Indigo Particle Core prepared in S1 is placed in a fluidized bed and coated with a 70% ethanol solution of hydroxypropyl methylcellulose E5 and polyethylene glycol 6000 by bottom spraying, so that the isolation layer completely covers the surface of the Indigo Particle Core until the weight gain is 8-12%. After drying, the isolation layer coated particles are obtained. S3. Eudragit S100, triethyl citrate, and talc are dissolved in 70% ethanol to prepare a bottom spray solution. The bottom spray solution is used to bottom spray coat the isolation layer coated particles obtained in S2 in a fluidized bed. The coating weight increases to 10-12% of the isolation layer coated particles. After drying, the formulation is obtained.

[0026] In this invention, in S1, the concentration of povidone K30 is 5-8%, the sieve is 18 mesh, the drying temperature is 60-70℃, the drying time is 1-2h, and the granules are sieved through a 20 mesh sieve.

[0027] In this invention, in S2, the fluidized bed process parameters are: inlet air temperature 55-65℃, outlet air temperature 40-48℃, material temperature 35-40℃, spraying speed 2-3mL / min, atomization pressure 0.2-0.3MPa; and drying time 20-30min.

[0028] In this invention, the process parameters in S3 are: inlet air temperature 60-70℃, outlet air temperature 45-50℃, material temperature 38-42℃, spraying speed 2-3mL / min, and atomization pressure 0.25-0.35MPa.

[0029] In this invention, in step S3, the drying temperature is 55-65℃, the drying time is 1-1.5h, and the granules are passed through a 20-mesh sieve.

[0030] The above-described oral colon-release formulation of indigo naturalis is used in the preparation of drugs for treating or improving ulcerative colitis.

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims and are all within the protection scope of the present invention.

[0032] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0033] Unless otherwise defined, the technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the use of related terms herein is merely for the purpose of describing particular embodiments and is not intended to limit this application.

[0034] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0035] Example 1 This invention provides an oral colon-release formulation of indigo naturalis, comprising the following raw materials: Indigo naturalis granule core: 2g indigo naturalis fine powder, 3g microcrystalline cellulose, 0.5g povidone K30 (PVP K30); isolation layer: 1g hydroxypropyl methylcellulose E5 (HPMC E5), 0.2g polyethylene glycol 6000 (PEG-6000); colon-targeting coating layer: 1.2g Eudragit S100, 0.24g triethyl citrate, 0.3g talc.

[0036] Its preparation method is as follows: S1. Preparation of Indigo Granule Core: Indigo fine powder and microcrystalline cellulose are mixed evenly, and 5% of 70% ethanol solution of povidone K30 is added to make a soft material. The soft material is granulated by passing it through an 18-mesh sieve, dried at 60℃ for 1.5h, and granulated by passing it through a 20-mesh sieve to obtain Indigo Granule Core. S2. Coating the Indigo Particle Core with an Isolation Layer: The Indigo Particle Core prepared in S1 is placed in a fluidized bed and coated with a 70% ethanol solution of hydroxypropyl methylcellulose E5 and polyethylene glycol 6000 by bottom spraying, so that the isolation layer completely covers the surface of the Indigo Particle Core until the weight gain is 10%. After drying, the isolation layer coated particles are obtained. The fluidized bed process parameters are: inlet air temperature 60℃, outlet air temperature 45℃, material temperature 38℃, spraying speed 2.5mL / min, atomization pressure 0.2MPa; drying time is 30min.

[0037] S3. Eudragit S100, triethyl citrate, and talc are dissolved in 70% ethanol to prepare a bottom spray solution (solid content concentration of 15%-20%). The bottom spray solution is used to bottom spray coat the isolation layer coated particles obtained in S2 in a fluidized bed. The coating weight increases to 11% of the isolation layer coated particles. The particles are then dried by forced air and granulated to obtain the formulation.

[0038] The process parameters are: inlet air temperature 65℃, outlet air temperature 50℃, material temperature 40℃, spraying speed 2mL / min, and atomization pressure 0.25MPa. Drying is performed at 60℃ for 1 hour to remove residual solvent, followed by granulation through a 20-mesh sieve.

[0039] Example 2 The only difference between this embodiment and Example 1 is that: Indigo granule core: 3g indigo fine powder, 4.5g microcrystalline cellulose, 0.6g PVP K30; isolation layer: 1.5g HPMC E5, 0.3g PEG-6000; colon positioning coating layer: 2g Eudragit S100, 0.35g triethyl citrate, 0.45g talc, prepared by the same method as in Example 1.

[0040] Example 3 The only difference between this embodiment and Example 1 is that: Indigo granule core: 4g indigo fine powder, 6g microcrystalline cellulose, 0.8g PVP K30; isolation layer: 2g HPMC E5, 0.4g PEG-6000; colon positioning coating layer: 3g Eudragit S100, 0.5g triethyl citrate, 0.6g talc, and the preparation method is the same as in Example 1.

[0041] Example 4 The only difference between this embodiment and Embodiment 1 is that the drying temperature in S1 is changed to 65°C and the drying time is 1 hour.

[0042] Example 5 The only difference between this embodiment and embodiment 1 is that in S2, the inlet air temperature is 55℃ and the atomization pressure is 0.2MPa, while in S3, the inlet air temperature is 70℃ and the atomization pressure is 0.35MPa. All other conditions are the same.

[0043] Comparative Example 1 The only difference between this comparative example and Example 1 is that it does not include step S2 and the raw materials do not contain an isolation layer; all other conditions are the same.

[0044] Comparative Example 2 The only difference between this comparative example and Example 1 is that the isolation layer uses only HPMC E5 and does not contain PEG-6000; all other conditions are the same.

[0045] Comparative Example 3 The only difference between this comparative example and Example 1 is that the raw material for the indigo granules does not contain PVP K30; all other conditions are the same.

[0046] Comparative Example 4 The only difference between this comparative example and Example 1 is that triethyl citrate is not added to the colon-positioning coating layer; all other conditions are the same.

[0047] Comparative Example 5 The only difference between this comparative example and Example 1 is that a common gastric-soluble coating material was used instead of Eudragit S100; all other conditions were the same.

[0048] Comparative Example 6 The only difference between this comparative example and Example 1 is that the air inlet temperature in S3 is adjusted to 50°C, while all other conditions are the same.

[0049] Comparative Example 7 The only difference between this comparative example and Example 1 is that the weight gain of the colon-positioning coating layer is 9%, while all other conditions are the same.

[0050] Comparative Example 8 The only difference between this comparative example and Example 1 is that the weight gain of the colon-positioning coating layer is 13%, while all other conditions are the same.

[0051] Comparative Example 9 The only difference between this comparative example and Example 1 is that the fluidized bed bottom spray coating equipment in S2 and S3 is replaced with a traditional high-efficiency coating pan using a rotary coating method to coat the indigo granules. All other conditions are the same as in Example 1. The specific parameters for the rotary coating method are: coating pan rotation speed 20 rpm, material temperature 40℃, hot air temperature 55℃, atomization pressure 0.2 MPa, and intermittent spraying.

[0052] Comparative Example 10 The only difference between this comparative example and Example 1 is that in the isolation layer coating process of S2, the spraying speed was increased to 5 mL / min and the atomization pressure was reduced to 0.15 MPa, while all other conditions were the same.

[0053] Performance testing: I. Release rate test: The preparations prepared in Examples 1-5 and Comparative Examples 1-10 were tested according to the Dissolution and Release Determination Method in General Chapter 0931 of Part IV of the 2020 Chinese Pharmacopoeia. The rotation speed was 100 r / min and the medium temperature was 37±0.5℃. The cumulative release of indigo was measured sequentially in pH 1.2 hydrochloric acid solution (simulating gastric juice, 2 h), pH 6.0 buffer solution (simulating small intestinal juice, 2 h), and pH 7.5 buffer solution (simulating colonic juice, 2 h). The test results are shown in Table 1 and... Figure 1 As shown: Table 1 Release rate test results

[0054] As shown in Table 1, the 2-hour release rates of Examples 1-5 in simulated gastric fluid (pH 1.2) ranged from 2.6% to 3.3%, and in simulated small intestinal fluid (pH 6.0) ranged from 4.2% to 5.2%, all significantly lower than the conventional leakage threshold of 10%. However, the 2-hour release rates in simulated colonic fluid (pH 7.5) all exceeded 96.0%, reaching a maximum of 97.5%. The reason for this stable and excellent release behavior is as follows: All embodiments strictly adhere to the core features of a complete isolation layer + colonic coating weight gain of 10-12% + fluidized bed bottom spraying process. HPMC E5 and PEG-6000 form a dense and flexible isolation membrane, effectively avoiding coating defects and drug degradation caused by direct contact between indigo and Eudragit S100. The colonic coating weight gain is controlled at around 11%, which is exactly within the critical window of 10-12%, providing sufficient gastric acid barrier thickness while ensuring that the coating membrane can dissolve quickly and completely in the colonic pH environment. The fluidized bed bottom spraying process ensures the uniformity and density of the double-layer coating.

[0055] Even with slight differences in parameters such as the dosage of indigo naturalis (2-4g), drying temperature (60℃ or 65℃), fluidized bed inlet air temperature, and atomization pressure among the various embodiments, the release rate remained highly consistent, fully demonstrating its broad process adaptability and robustness. These results strongly prove that after oral administration, the formulation can completely resist the gastric and small intestinal environment, accurately reach the colon, and rapidly release the vast majority of the drug within 2 hours, achieving colon-targeted delivery of the active ingredient of indigo naturalis, laying a formulation foundation for the highly effective local treatment of ulcerative colitis.

[0056] In contrast, Comparative Example 1 showed a release rate as high as 26.8% at pH 1.2, but only 72.5% at pH 7.5. This is because, without an insulating layer, the Eudragit S100 coating solution directly contacts the hydrophobic indigo powder. The mismatch in surface properties between the two leads to poor adhesion of the coating layer, resulting in pinholes and cracks. Simultaneously, indigo in the indigo powder adsorbs and binds to the carboxyl groups of Eudragit S100, further compromising the coating integrity. Gastric acid seeps in through these defects, causing premature drug release. In the colon, premature drug consumption and conjugate formation significantly reduce the release rate.

[0057] Comparative Example 2 showed a release rate of 7.8% at pH 1.2 and only 86.2% at pH 7.5. The absence of PEG-6000 as a plasticizer increased the brittleness of the HPMC E5 barrier layer, leading to microcracks during airflow impact, drying shrinkage, and granulation. Small amounts of gastric acid seeped into the colon through these microcracks, resulting in uneven adhesion and incomplete release of Eudragit S100 due to the incomplete barrier layer.

[0058] Comparative Example 3 showed a release of 14.2% at pH 1.2 and only 80.5% at pH 7.5. PVP K30 is a key binder in wet granulation; its absence results in loose, brittle granules that generate a large amount of fine powder in the fluidized bed. This fine powder embeds into the coating layer, creating pores or causing uneven coating coverage. Gastric acid can then seep through these pores, hindering colonic release.

[0059] Comparative Example 4 showed a release of 5.5% at pH 1.2 and only 85.0% at pH 7.5. The absence of triethyl citrate as a plasticizer resulted in excessive stiffness and increased brittleness in the Eudragit S100 coating layer. During drying and storage, internal stress caused microcracks, allowing gastric acid to seep in and leading to incomplete release into the colon.

[0060] Comparative Example 5 showed 42.5% release at pH 1.2 and only 58.5% at pH 7.5. The gastric-soluble coating material is not pH-dependent and dissolves in gastric acid, resulting in significant drug disintegration and complete loss of colon-targeting function in the upper digestive tract.

[0061] Comparative Example 6 released 8.2% at pH 1.2 and only 84.5% at pH 7.5. The low inlet air temperature resulted in insufficient ethanol solvent evaporation, preventing the coating solution from drying and solidifying into a film on the particle surface in time. This caused droplets to merge, resulting in flow or the formation of pores, decreased coating density, increased gastric acid permeability, and incomplete colonic release due to structural defects in the coating layer.

[0062] Comparative Example 7 released 15.5% at pH 1.2, exceeding the 10% warning line, and only 88.5% at pH 7.5. The 9% weight gain corresponded to an excessively thin coating layer, which could not provide a sufficiently robust gastric acid barrier. Gastric acid could lead to premature drug release through minute permeation and mechanical damage to the thinner membrane layer, demonstrating that 10% is the critical lower limit for blocking gastric acid leakage.

[0063] Comparative Example 8 showed only 1.2% release at pH 1.2, but only 68.5% release after 2 hours at pH 7.5. The 13% weight gain of the coating layer was too thick. Although the gastric acid barrier was enhanced, Eudragit S100 required a longer time to completely dissolve in the colonic environment of pH 7.5, and could not be fully released within 2 hours, resulting in a significant delay in drug release. This demonstrates that 12% is the critical upper limit for achieving rapid colonic release.

[0064] Comparative Example 9 released 9.0% at pH 1.2, which is close to the leakage threshold, and only 87.0% at pH 7.5. Traditional coating pans rely on tumbling motion, which cannot achieve an ideal suspension fluidization state for small-diameter particles with a 20-mesh sieve. Particles are prone to sticking together, the coating liquid distribution is extremely uneven, some particles have excessively thick exposed portions, and friction between particles and the pan wall causes mechanical damage, resulting in an overall coating layer quality that is significantly inferior to that of fluidized bed processes.

[0065] Comparative Example 10 released 11.5% at pH 1.2 and only 85.5% at pH 7.5. Excessive spraying speed caused the coating solution supply to exceed the drying capacity, resulting in particle adhesion through liquid bridges. After drying, this adhesion resulted in partial exposure of the isolation layer. Insufficient atomization pressure caused large, unevenly distributed droplets, preventing the formation of a continuous and complete film. The exposed indigo particles came into direct contact with Eudragit S100, leading to adsorption degradation and coating defects similar to those in Comparative Example 1.

[0066] II. Animal Modeling Detection: One hundred and seventy SPF-grade male C57BL / 6 mice, aged 6-8 weeks and weighing 20±2g, were selected and divided into 17 groups of 10 mice each. These groups were: normal control group, model control group, Example 1 group, Example 2 group, Example 3 group, Example 4 group, Example 5 group, Comparative Example 1 group, Comparative Example 2 group, Comparative Example 3 group, Comparative Example 4 group, Comparative Example 5 group, Comparative Example 6 group, Comparative Example 7 group, Comparative Example 8 group, Comparative Example 9 group, and Comparative Example 10 group.

[0067] Procedure: Except for the normal control group which drank pure water, all mice had free access to 3% DSS solution, which was changed daily. Starting from day 1 of modeling, each treatment group was administered the drug once daily by gavage (10 mL / kg), while the normal and model control groups were administered an equal volume of physiological saline by gavage. Drug administration and modeling were performed simultaneously for 7 consecutive days.

[0068] Twenty-four hours after the last administration, i.e., on day 8 of modeling, mice were weighed, their DAI scores were assessed, and they were euthanized by cervical dislocation. The entire colon (from the ileocecal junction to the anus) was dissected and its length measured. The colon tissue from the most prominent lesion was harvested; a portion was fixed in 4% paraformaldehyde for pathological sections, and the other portion was homogenized for the determination of inflammatory factors and indigo content. The experimental results are shown in Tables 2-3 and 2-3. Figure 2-3 As shown.

[0069] Table 2. Modeling Experiment Results

[0070] ΔΔ P < 0.01 vs. normal control group P<0.01 vs. model control group p<0.05 vs Example 1 group.

[0071] Table 2 shows that compared with the normal control group, the model control group had the following characteristics: DAI score increased from 0.2 to 3.6, colon length decreased from 7.9 cm to 5.0 cm, and pathological score increased from 0.3 to 3.3 (an 11-fold increase). All three indicators are labeled. ΔΔ p<0.01 indicates that the DSS-induced acute ulcerative colitis model was successfully established, with mice exhibiting significant weight loss, diarrhea, bloody stools, inflammatory infiltration of the colonic tissue, and crypt destruction. This provides a reliable pathological basis for subsequent drug efficacy evaluation.

[0072] Compared with the model control group, in Examples 1-5: DAI scores decreased to 1.0-1.2, colon length recovered to 7.1-7.3 cm, approaching normal levels, and pathological scores decreased to 0.8-1.0. All examples are labeled. p<0.01, demonstrating that the preparations obtained in Examples 1-5 have extremely significant therapeutic effects. Furthermore, there were almost no differences in data among the groups with different dosages of indigo (2g, 3g, 4g) and minor adjustments to process parameters, indicating that this technical solution has broad prescription adaptability and process robustness.

[0073] The DAI scores (2.2-3.1), colon length (5.4-6.2 cm), and pathological scores (1.9-2.9) of Comparative Examples 1-10 were significantly worse than those of Example 1 group. (p<0.05), and the indices of some comparative examples (comparative examples 1, 3, and 5) are close to those of the model control group. The fundamental reason for this result is: Each comparative example exhibited various defects, including a missing isolation layer, incomplete isolation layer components, lack of binder or plasticizer, incorrect coating material, coating weight gain deviating from the 10-12% critical window, improper process temperature, incomplete isolation layer coating, or the use of a traditional coating pan. These defects led to premature leakage of the coating layer in gastric acid or delayed release into the colon, preventing the drug from reaching an effective therapeutic concentration in the colon. Although the degree of failure varied among the different comparative examples (from partial to complete failure), none achieved the near-normal therapeutic effect of Example 1 group, thus demonstrating the synergistic necessity of the three core elements of this invention: a complete isolation layer, critical weight gain, and fluidized bed bottom spray.

[0074] Table 3. Levels of inflammatory factors and indigo content in the colon tissue of mice in each group

[0075] ΔΔ P < 0.01 vs. normal control group P<0.01 vs. model control group p<0.05 vs Example 1 group.

[0076] Table 3 shows that in the normal control group, the colon tissue of mice contained TNF-α of 28 pg / mg, IL-6 of 20 pg / mg, and IL-10 of 88 pg / mg, exhibiting a balance between low pro-inflammatory and high anti-inflammatory levels. In the model control group, TNF-α increased to 148 pg / mg, IL-6 increased to 102 pg / mg, and IL-10 decreased to 30 pg / mg. All three indicators were clearly labeled. ΔΔ p<0.01 indicates that DSS induced a severe inflammatory response, with massive activation of macrophages, explosive release of pro-inflammatory factors, and suppression of anti-inflammatory factors. This is a typical immune dysregulation feature of ulcerative colitis.

[0077] Compared with the model control group, in Examples 1-5: TNF-α decreased to 41-46 pg / mg, IL-6 decreased to 27-31 pg / mg, and IL-10 increased to 78-83 pg / mg, returning to near-normal levels. All examples were labeled. p<0.01 demonstrates that the formulation of this invention can significantly inhibit pro-inflammatory factors, upregulate anti-inflammatory factors, and restore intestinal immune homeostasis. This effect is attributed to the synergistic anti-inflammatory effects of multiple components such as indigo and indirubin through multiple pathways such as PI3K / Akt and HIF-1, as well as colon-targeted delivery that enables the drug to reach high concentrations at the lesion site.

[0078] The levels of pro-inflammatory cytokines TNF-α (78-118 pg / mg) and IL-6 (52-82 pg / mg) in Comparative Examples 1-10 were significantly higher than those in Example 1, while the levels of anti-inflammatory cytokines IL-10 (38-60 pg / mg) and Indigofera colonica (0.65-1.35 μg / g) were significantly lower than those in Example 1. p<0.05. Among them, Comparative Example 5 (gastric coating), Comparative Example 1 (no separator), and Comparative Example 3 (no PVP K30) had the lowest colonic indigo content (0.65-0.92 μg / g), and their inflammatory factor levels were closest to the model control group; while Comparative Example 2 (no PEG separator) and Comparative Example 10 (incomplete separator) had relatively higher indigo content (1.28-1.35 μg / g), but still less than half of that in Example 1. This result indicates that: The colonic indigo content showed a clear positive correlation with the anti-inflammatory effect. In the comparative examples, defects in the coating layer or process deviations led to the destruction of the active ingredient in indigo by gastric acid before reaching the colon, premature release, or incomplete release within the colon, resulting in insufficient local drug concentration. Consequently, these comparative examples could not effectively inhibit the overexpression of TNF-α and IL-6, nor could they restore IL-10 to normal levels. All comparative examples failed to reproduce the anti-inflammatory and targeted delivery effects of Example 1 group, further confirming the superiority and irreplaceability of the technical solution of this invention.

[0079] Therefore, this invention employs the aforementioned oral colonic-release formulation of indigo naturalis, its preparation method, and its application. Through a three-in-one technical solution of complete isolation layer, critical colonic coating weight gain, and fluidized bed bottom spraying process, it solves key problems such as coating defects, drug degradation, and insufficient release precision in the colonic targeted delivery of indigo naturalis from the source of formulation. This enables the active ingredient of indigo naturalis to act on the lesion site in its complete chemical form, in the colonic environment, and at a sufficient dose, achieving a highly efficient, safe, and stable therapeutic effect for ulcerative colitis.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An oral colon-release formulation of indigo naturalis, characterized in that: The formulation includes an indigo granule core, an isolation layer, and a colon-targeting coating layer. The isolation layer completely covers the surface of the indigo granule core, and the colon-targeting coating layer covers the surface of the isolation layer. The administration method of the formulation is: release directly into the colon via oral administration.

2. The oral colon-release formulation of indigo naturalis according to claim 1, characterized in that: The indigo granule core consists of 2-4 parts by weight of indigo fine powder, 3-6 parts by weight of microcrystalline cellulose, and 0.4-0.8 parts by weight of povidone K30; the isolation layer consists of 1-2 parts by weight of hydroxypropyl methylcellulose E5 and 0.2-0.4 parts by weight of polyethylene glycol 6000; the colon-positioning coating layer consists of 1-3 parts by weight of Eudragit S100, 0.2-0.5 parts by weight of triethyl citrate, and 0.3-0.6 parts by weight of talc.

3. The oral colon-release formulation of indigo naturalis according to claim 1, characterized in that: The indigo granule core consists of 2 parts by weight of indigo fine powder, 3 parts by weight of microcrystalline cellulose and 0.5 parts by weight of povidone K30; the isolation layer consists of 1 part by weight of hydroxypropyl methylcellulose E5 and 0.2 parts by weight of polyethylene glycol 6000; the colon-positioning coating layer consists of 1.2 parts by weight of Eudragit S100, 0.24 parts by weight of triethyl citrate and 0.3 parts by weight of talc.

4. The oral colon-release formulation of indigo naturalis according to claim 1, characterized in that: The weight gain of the colon-positioning coating layer is 10-12% of the total weight of the isolation layer and the indigo granule core, and the weight gain of the isolation layer is 8-12% of the weight of the indigo granule core.

5. The method for preparing an oral colon-release formulation of indigo naturalis as described in claim 1, characterized in that: Includes the following steps: S1. Preparation of Indigo Particle Core: Indigo fine powder and microcrystalline cellulose are mixed evenly, and a 70% ethanol solution of povidone K30 is added to make a soft material. The soft material is sieved and granulated, dried and sized to obtain Indigo Particle Core. S2. Coating the Indigo Particle Core with an Isolation Layer: The Indigo Particle Core prepared in S1 is placed in a fluidized bed and coated with a 70% ethanol solution of hydroxypropyl methylcellulose E5 and polyethylene glycol 6000 by bottom spraying, so that the isolation layer completely covers the surface of the Indigo Particle Core until the weight gain is 8-12%. After drying, the isolation layer coated particles are obtained. S3. Eudragit S100, triethyl citrate, and talc are dissolved in 70% ethanol to prepare a bottom spray solution. The bottom spray solution is used to bottom spray coat the isolation layer coated particles obtained in S2 in a fluidized bed. The coating weight increases to 10-12% of the isolation layer coated particles. After drying, the formulation is obtained.

6. The method for preparing an oral colon-release formulation of indigo naturalis according to claim 5, characterized in that: In S1, the concentration of povidone K30 is 5-8%, the sieve is 18 mesh, the drying temperature is 60-70℃, the drying time is 1-2 hours, and the granules are sieved through a 20 mesh sieve.

7. The method for preparing an oral colon-release formulation of indigo naturalis according to claim 5, characterized in that: In S2, the fluidized bed process parameters are: inlet air temperature 55-65℃, outlet air temperature 40-48℃, material temperature 35-40℃, spraying speed 2-3mL / min, atomization pressure 0.2-0.3MPa; drying time is 20-30min.

8. The method for preparing an oral colon-release formulation of indigo naturalis according to claim 5, characterized in that: In S3, the process parameters are: inlet air temperature 60-70℃, outlet air temperature 45-50℃, material temperature 38-42℃, spraying speed 2-3mL / min, and atomization pressure 0.25-0.35MPa.

9. The method for preparing an oral colon-release formulation of indigo naturalis according to claim 5, characterized in that: In S3, the drying temperature is 55-65℃, the drying time is 1-1.5h, and the granules are passed through a 20-mesh sieve.

10. The use of an oral colon-release formulation of indigo naturalis as described in any one of claims 1-4 in the preparation of a medicament for treating or improving ulcerative colitis.

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