The formation of a host-guest inclusion complex system between β-cyclodextrin and baicalin and its dissolution characteristics

Molecular Interaction and Solubilization Efficiency of Neohesperidin in Ternary Systems with Hydroxypropyl-β-cyclodextrin and Meglumine

The solubilization of poorly water-soluble natural bioactive compounds remains a significant challenge. This study aims to design a ternary inclusion system to enhance the solubility of the poorly water-soluble compound Neohesperidin (NH). Soluble ternary cyclodextrin complexations (t-CDs) containing NH, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), and meglumine (MEG) were prepared and optimized. The optimized t-CDs were further characterized using Scanning Electron Microscopy (SEM), Powder X-ray Diffraction (PXRD), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR), and molecular docking (MD) techniques. The results suggested that NH formed was associated with MEG through hydrogen bonds with MEG, and was subsequently incorporated into the hydrophobic cavity of HP-β-CD, which may be a key factor in improving its solubility. The solubility of NH in water at 37 °C increased significantly from 0.16 mg/mL to 5.81 mg/mL in the optimized t-CDs (NH/MEG/HP-β-CD).

Chemical modification of β-cyclodextrin towards hydrogel formation

β-CD is a cyclic oligosaccharide, which has trunked cone like structure. The unique structure makes it efficient for numerous applications. Though, the native β-CD has many issues like low solubility, absence of sufficient functionalities and lower complexation ability with guest molecules. One of the most effective paths to increase the efficiency of cyclodextrins is the generation of polycyclodextrins. In this perspective article, we have summarized the recent reports on the synthetic methods towards the modification of β-CD. Besides, this article reviews the current improvements of two types of β-CD centered supramolecular hydrogels: one is supramolecular hydrogels prepared from CD-based poly(pseudo)rotaxanes and the other is supramolecular hydrogels developed through the host-guest interaction between small guest molecules and CDs. The Polycyclodextrins have established noteworthy applications in several areas ranging from adsorbents for organic pollutants removal to effective carriers of bioactive agents.

The protective effects of baicalin for respiratory diseases: an update and future perspectives

Background: Respiratory diseases are common and frequent diseases. Due to the high pathogenicity and side effects of respiratory diseases, the discovery of new strategies for drug treatment is a hot area of research. Scutellaria baicalensis Georgi (SBG) has been used as a medicinal herb in China for over 2000 years. Baicalin (BA) is a flavonoid active ingredient extracted from SBG that BA has been found to exert various pharmacological effects against respiratory diseases. However, there is no comprehensive review of the mechanism of the effects of BA in treating respiratory diseases. This review aims to summarize the current pharmacokinetics of BA, baicalin-loaded nano-delivery system, and its molecular mechanisms and therapeutical effects for treating respiratory diseases.

Method: This review reviewed databases such as PubMed, NCBI, and Web of Science from their inception to 13 December 2022, in which literature was related to “baicalin”, “Scutellaria baicalensis Georgi”, “COVID-19”, “acute lung injury”, “pulmonary arterial hypertension”, “asthma”, “chronic obstructive pulmonary disease”, “pulmonary fibrosis”, “lung cancer”, “pharmacokinetics”, “liposomes”, “nano-emulsions”, “micelles”, “phospholipid complexes”, “solid dispersions”, “inclusion complexes”, and other terms.

Result: The pharmacokinetics of BA involves mainly gastrointestinal hydrolysis, the enteroglycoside cycle, multiple metabolic pathways, and excretion in bile and urine. Due to the poor bioavailability and solubility of BA, liposomes, nano-emulsions, micelles, phospholipid complexes, solid dispersions, and inclusion complexes of BA have been developed to improve its bioavailability, lung targeting, and solubility. BA exerts potent effects mainly by mediating upstream oxidative stress, inflammation, apoptosis, and immune response pathways. It regulates are the NF-κB, PI3K/AKT, TGF-β/Smad, Nrf2/HO-1, and ERK/GSK3β pathways.

Conclusion: This review presents comprehensive information on BA about pharmacokinetics, baicalin-loaded nano-delivery system, and its therapeutic effects and potential pharmacological mechanisms in respiratory diseases. The available studies suggest that BA has excellent possible treatment of respiratory diseases and is worthy of further investigation and development.

Enhanced Efficacy of Carvedilol by Utilization of Solid Dispersion and Other Novel Strategies: A Review

Carvedilol is classified as a second class drug of Biopharmaceutical classification system (BCS), and it is an excellent beta blocker and vasodilating agent. It is used in a diverse range of disease states. Despite having tremendous advantages, the drug cannot be used effectively and productively due to aquaphobicity and poor bioavailability. To overcome this limitation, numerous novel approaches and tactics have been introduced over the past few years, such as Selfmicro emulsifying drug delivery systems (SMEDDS), nanoparticles, solid dispersions and liposomal drug delivery. The present review aims to accentuate the role of solid dispersion in improving the dissolution profile and aqua solubility of carvedilol and also to emphasize other novel formulations of carvedilol proposed to prevail the limitations of carvedilol. Solid dispersion and other novel approaches were found to play a significant role in overcoming the drawbacks of carvedilol, among which solid dispersion is the most feasible and effective approach being used worldwide. Reduced particle size, more wettability, and large surface area are obtained by the implementation of solid dispersion technique, hence improving carvedilol solubility and bioavailability.

Baicalin-berberine complex nanocrystals orally promote the co-absorption of two components

Baicalin (BA)-berberine (BBR) have been proposed as the couple in the prevention and treatment of numerous diseases due to their multiple functional attributes. However, with regard to certain factors involving unsatisfactory aqueous solubility and low bioavailability associated with its clinical application, there is need for continuous researches by scientist. In this study, after successfully preparing BA-BBR complex, BA-BBR complex nanocrystals were obtained through high-pressure homogenization and evaluated (in vitro and in vivo). The particle size, distribution, morphology, and crystalline properties for the optimal BA-BBR complex nanocrystals were characterized by the use of scanning electron microscope, dynamic light scattering, powder X-ray diffraction, and differential scanning calorimetry. The particle size and poly-dispersity index of BA-BBR complex nanocrystals were 318.40 ± 3.32 nm and 0.26 ± 0.03, respectively. In addition, evaluation of the in vitro dissolution extent indicated that BA and BBR in BA-BBR complex nanocrystals were 3.30- and 2.35-fold than BA-BBR complex. Subsequently, single-pass intestinal perfusion combined with microdialysis test and oral pharmacokinetics in SD rats was employed to evaluate the in vivo absorption improvement of BA-BBR complex nanocrystals. The pharmacokinetics results exhibited that the area under curve of BA and BBR in the BA-BBR complex nanocrystals group were 622.65 ± 456.95 h·ng/ml and 167.28 ± 78.87 h·ng/ml, respectively, which were separately 7.49- and 2.64-fold than the complex coarse suspension. In conclusion, the above results indicate that the developed and optimized BA-BBR complex nanocrystals could improve the dissolution rate and extent and oral bioavailability, as well as facilitate the co-absorption of the drug prescriptions BA and BBR.

Role of baicalin as a potential therapeutic agent in hepatobiliary and gastrointestinal disorders: A review

Baicalin is a natural bioactive compound derived from Scutellaria baicalensis, which is extensively used in traditional Chinese medicine. A literature survey demonstrated the broad spectrum of health benefits of baicalin such as antioxidant, anticancer, anti-inflammatory, antimicrobial, cardio-protective, hepatoprotective, renal protective, and neuroprotective properties. Baicalin is hydrolyzed to its metabolite baicalein by the action of gut microbiota, which is further reconverted to baicalin via phase 2 metabolism in the liver. Many studies have suggested that baicalin exhibits therapeutic potential against several types of hepatic disorders including hepatic fibrosis, xenobiotic-induced liver injury, fatty liver disease, viral hepatitis, cholestasis, ulcerative colitis, hepatocellular and colorectal cancer. During in vitro and in vivo examinations, it has been observed that baicalin showed a protective role against liver and gut-associated abnormalities by modifying several signaling pathways such as nuclear factor-kappa B, transforming growth factor beta 1/SMAD3, sirtuin 1, p38/mitogen-activated protein kinase/Janus kinase, and calcium/calmodulin-dependent protein kinase kinaseβ/adenosine monophosphate-activated protein kinase/acetyl-coenzyme A carboxylase pathways. Furthermore, baicalin also regulates the expression of fibrotic genes such as smooth muscle actin, connective tissue growth factor, β-catenin, and inflammatory cytokines such as interferon gamma, interleukin-6 (IL-6), tumor necrosis factor-alpha, and IL-1β, and attenuates the production of apoptotic proteins such as caspase-3, caspase-9 and B-cell lymphoma 2. However, due to its low solubility and poor bioavailability, widespread therapeutic applications of baicalin still remain a challenge. This review summarized the hepatic and gastrointestinal protective attributes of baicalin with an emphasis on the molecular mechanisms that regulate the interaction of baicalin with the gut microbiota.

Application of molecular docking in elaborating molecular mechanisms and interactions of supramolecular cyclodextrin

The cyclodextrin (CD)-based supramolecular nanomedicines have attracted growing interest because of their superior characteristics, including desirable biocompatibility, low toxicity, unique molecular structure and easy functionalization. The smart structures of CD impart host-guest interaction for meeting the multifunctional needs of disease therapy. However, it faces challenges in formulation design and inclusion mechanism clarification of the functional supramolecular assemblies owing to the complicated structures and mechanisms. Fortunately, molecular docking helps the researchers to comprehend the interaction between the drug and the target molecule for achieving high-through screening from the database. In this review, we summarized the category and characteristics of molecular docking along with the properties and applications of CD. Significantly, we highlighted the application of molecular docking in elaborating molecular mechanisms and simulating complex structures at molecular levels. The issues and development of CD and molecular docking were also presented to provide beneficial reference and new insights for supramolecular nano-systems.

Novel bioemulsomes for baicalin oral lymphatic targeting: development, optimization and pharmacokinetics

Aim: The aim of this study was to elaborate on 'bioemulsomes,' novel biocompatible lipoprotein analogs for effective lymphatic transport of baicalin (BCL). Methods: BCL bioemulsomes were developed and optimized and in vitro physicochemical characterization performed. The bioavailability of BCL bioemulsomes compared with free BCL was investigated using in vivo pharmacokinetics studies. Finally, BCL lymphatic transport was assessed via cycloheximide blockade assay. Results: Optimized BCL-loaded nanoemulsomes showed promising in vitro characteristics that favor lymphatic targeting. In vivo pharmacokinetics showed a significant improvement in bioavailability over free BCL. A significant decrease in BCL emulsome absorption (33%) was exhibited after chemical blockage of the lymphatic pathway, confirming the lymphatic transport potential. Conclusion: Bioemulsomes could be a promising tool for bypassing BCL oral delivery hurdles as well as lymphatic transport, paving the way for potential treatment of lymphoma.

Baicalin mediated regulation of key signaling pathways in cancer

Baicalin has been widely investigated against different types of malignancies both at the cellular and molecular levels over the past few years. Due to its remarkable anti-proliferative potential in numerous cancer cell lines, it has created immense interest as a potential chemotherapeutic modality compared to other flavonoids. Thus, this review focuses on the recent accomplishments of baicalin and its limitations in cancer prevention and treatment. Further, combination studies and nanoformulations using baicalin to treat cancer along with the metabolism, bioavailability, toxicity, and pharmacokinetics have been discussed. The present review explains biological source, and anti-proliferative potential of baicalin against cancers including breast, colon, hepatic, leukemia, lung, and skin, as well as the relevant mechanism of action to modulate diverse signaling pathways including apoptosis, cell cycle, invasion, and migration, angiogenesis, and autophagy. The anticancer mechanism of baicalin in orthotropic and xenograft mice models have been deliberated. The combination studies of baicalin in novel therapies as chemotherapeutic adjuvants have also been summarized. The low bioavailability, fast metabolism, and poor solubility, and other significant factors that limit the clinical use of baicalin have been examined as a challenge. The improvement in the pharmacokinetics and pharmacodynamics of baicalin with newer approaches and the gaps are highlighted, which could establish baicalin as an effective and safe compound for cancer treatment as well as help to translate its potential from bench to bedside.

On Complex Formation between 5-Fluorouracil and β-Cyclodextrin in Solution and in the Solid State: IR Markers and Detection of Short-Lived Complexes by Diffusion NMR

In this work, the nuclear magnetic resonance (NMR) and IR spectroscopic markers of the complexation between 5-fluorouracil (5-FU) and β-cyclodextrin (β-CD) in solid state and in aqueous solution are investigated. In the attenuated total reflectance(ATR) spectra of 5-FU/β-CD products obtained by physical mixing, kneading and co-precipitation, we have identified the two most promising marker bands that could be used to detect complex formations: the C=O and C-F stretching bands of 5-FU that experience a blue shift by ca. 8 and 2 cm-1 upon complexation. The aqueous solutions were studied by NMR spectroscopy. As routine NMR spectra did not show any signs of complexation, we have analyzed the diffusion attenuation of spin-echo signals and the dependence of the population factor of slowly diffusing components on the diffusion time (diffusion NMR of pulsed-field gradient (PFG) NMR). The analysis has revealed that, at each moment, ~60% of 5-FU molecules form a complex with β-CD and its lifetime is ca. 13.5 ms. It is likely to be an inclusion complex, judging from the independence of the diffusion coefficient of β-CD on complexation. The obtained results could be important for future attempts of finding better methods of targeted anticancer drug delivery.

Antiviral effect of phytochemicals from medicinal plants: Applications and drug delivery strategies

Viral infections affect three to five million patients annually. While commonly used antivirals often show limited efficacy and serious adverse effects, herbal extracts have been in use for medicinal purposes since ancient times and are known for their antiviral properties and more tolerable side effects. Thus, naturally based pharmacotherapy may be a proper alternative for treating viral diseases. With that in mind, various pharmaceutical formulations and delivery systems including micelles, nanoparticles, nanosuspensions, solid dispersions, microspheres and crystals, self-nanoemulsifying and self-microemulsifying drug delivery systems (SNEDDS and SMEDDS) have been developed and used for antiviral delivery of natural products. These diverse technologies offer effective and reliable delivery of medicinal phytochemicals. Given the challenges and possibilities of antiviral treatment, this review provides the verified data on the medicinal plants and related herbal substances with antiviral activity, as well as applied strategies for the delivery of these plant extracts and biologically active phytochemicals. Graphical Abstract.

Regulatory Mechanisms of Baicalin in Cardiovascular Diseases: A Review

Cardiovascular diseases (CVDs) is the leading cause of high morbidity and mortality worldwide, which emphasizes the urgent necessity to develop new pharmacotherapies. In eastern countries, traditional Chinese medicine Scutellaria baicalensis Georgi has been used clinically for thousands of years. Baicalin is one of the main active ingredients extracted from Chinese herbal medicine S. baicalensis. Emerging evidence has established that baicalin improves chronic inflammation, immune imbalance, disturbances in lipid metabolism, apoptosis and oxidative stress. Thereby it offers beneficial roles against the initiation and progression of CVDs such as atherosclerosis, hypertension, myocardial infarction and reperfusion, and heart failure. In this review, we summarize the pharmacological features and relevant mechanisms by which baicalin regulates CVDs in the hope to reveal its application for CVDs prevention and/or therapy.

Fabrication and evaluation of fast disintegrating pellets of cilostazol

The present study was designed to formulate and develop fast disintegrating pellets of poorly soluble model drug (cilostazol) by reducing the proportion of micro-crystalline cellulose with pre-gelatinized starch (PGS), lactose and chitosan. The bioavailability enhancement of a model drug was achieved by preparing inclusion complex with Captisol® (Sulfobutyl Ether β cyclodextrin - SBE-β-CD). Extrusion-spheronization technique was used to formulate pellets. Placket-Burman design was used for the initial screening of most significant factors such as screen size (mm), ratio of micro crystalline cellulose: PGS + lactose + chitosan and % of HPMC which affects pellet properties. The inclusion complex of drug and Captisol^® (SBE-β-CD) was prepared by Solvent Evaporation method and were incorporated into pellets in a predefined proportion. Formulation was optimized by using 3² full factorial design, the optimized batch was selected on the basis of dependent variables such as % yield, pellet size, disintegration time and % Cumulative drug release (%CDR), the obtained results were 87.15%, 0.75 mm, 13 min and 91.024% respectively. Differential scanning calorimetry (DSC) and Fourier transform infrared spectrometry (FTIR) study revealed no significant interaction between drug and polymer. Scanning electron microscopy (SEM) confirmed uniform and spherical shaped pellets having pores on the surface which facilitates wicking action and fast disintegrating property of pellets. A design space was constructed to meet the desirable target and optimized batch. The scope of study can further extended to hydrophobic molecules which may useful due to rapid disintegration and enhanced dissolution rate.

Baicalin encapsulating lipid-surfactant conjugate based nanomicelles: Preparation, characterization and anticancer activity

Lung cancer is one of the most common malignant tumors and emerged as one of the leading causes of cancer-related death worldwide. Surgical resection can be a curative treatment for early stage but the most of lung cancer patients are diagnosed at an advanced stage when the pulmonary tumor has been invaded beyond the respiratory system. Therefore, chemotherapy is suitable for curing metastasized tumor. Baicalin (BL) is a flavonoid which has been studied in the treatment of several types of cancer including lung cancer. However, its low solubility in water and non-specificity impede its practical utilization. Hence, we have reported a stearic acid and pluronic F68 conjugated nanomicelles (PF68-SA) system to improve therapeutic efficacy of BL. Solvent evaporation method was used to prepare the BL-loaded PF68-SA nanomicelles (BLNM). The designed BLNM were characterized for the particle size, surface charge, critical micelle concentration, colloidal stability, morphology, and total drug content. BLNM formulation showed improved toxicity of BL against A549 human lung cancer cells in cytotoxicity assay. Further, apoptosis study also depicted BLNM-induced cell death in A549 cells. Therefore, the synthesized fatty acid-modified polymeric nanomicellar system could be useful in overcoming the stability and low therapeutic efficacy issues of hydrophobic anticancer drugs like BL and delivering them to the cancer cells.

Applying Different Techniques to Improve the Bioavailability of Candesartan Cilexetil Antihypertensive Drug

Purpose

The objective of this study was to compare different techniques to enhance the solubility and dissolution rate, and hence the bioavailability of candesartan cilexetil.

Methods

To achieve this target, various techniques were employed such as solid dispersions, inclusion complexes, and preparation of candesartan nanoparticles. Following the preparations, all samples were characterized for their physicochemical properties, and the samples of the best results were subjected to further bioavailability studies.

Results

Results of dissolution studies revealed an increase in the dissolution rate of all samples. The highest dissolution rate was achieved using solid dispersion of the drug with PVP K-90 (1:4). Physicochemical investigations (XR, DSC, and FT-IR) suggested formation of hydrogen bonding and changing in the crystalline structure of the drug. Regarding the inclusion complexes, more stable complex was formed between HP-β-CD and CC compared to β-CD, as indicated by phase solubility diagrams. Antisolvent method resulted in the preparation of stable nanoparticles, as indicated by ζ potential, with average particle size of 238.9 ± 19.25 nm using PVP K-90 as a hydrophilic polymer. The best sample that gave the highest dissolution rate (CC/PVP K-90 1:4) was allowed for further pharmacokinetic studies using UPLC MS/MS assay of rabbit plasma. Results showed a significant increase in the bioavailability of CC from ~15% to ~48%.

Conclusion

The bioavailability of CC was significantly improved from ~15% to ~48% when formulated as SDs with PVP K-90 with 1:4 drug:polymer ratio.

Charting the structural and thermodynamic determinants in phenolic acid natural product - cyclodextrin encapsulations

Cyclodextrins are pliable platforms that have served to optimize the pharmaceutic profile of numerous compounds and to enhance the stability of natural food additives. Caffeic and rosmarinic acid are natural products with proven health benefits, though their full therapeutic potential has not been exploited. To enhance their pharmaceutic profile, we developed cyclodextrin-based formulates and unveiled their thermodynamic and structural principles. The complexes' stoichiometry was determined by ESI-MS. Solid-state and liquid NMR spectroscopy revealed the interactions and the topographical location of the caffeic and rosmarinic acid inside the cyclodextrin cavity. The theoretically analyzed HP-β-CD's degree of substitution (DS) of caffeic and rosmarinic acids can explain the intensities obtained by 2D NOESY experiments. The thermodynamics and the affinity of the complexes were evaluated through isothermal titration calorimetry. In addition, the rosmarinic and caffeic acids as, also, their complexes showed considerable antimicrobial activity against common food spoilage and pathogenic bacteria. The generated data could provide the basis to understand the structural and thermodynamic determinants implicated in natural products - CD recognition and to develop platforms for the optimization of their pharmaceutical and stability profiles in order to be utilized as safe and stable natural antimicrobial food additives.Communicated by Ramaswamy H. Sarma.

Cyclodextrin potentiometric sensors based on selective recognition sites for procainamide: Comparative and theoretical study

Polyvinyl chloride (PVC) membrane sensors were constructed and developed for the determination of procainamide HCl (PR). Three membrane sensors incorporating α-, β- and γ- cyclodextrin (CD) as ionophores with potassium tetrakis (4-chlorophenyl) borate (KTpClPB) as the ion additive, o-nitro phenyl ether (o-NPOE) as the plasticizer and a PVC matrix. The reaction mechanisms were based on inclusion complexes. The developed α- and β- CD sensors exhibited near-Nernstian profile, whereas γ- CD showed a non-Nernstian response. At pH 4 -8, the sensors exhibited a calibration range for PR of 10-3 to 10−6, and the detection limits were 2.40 × 10-6, 2.12 × 10-6, 2.40 × 10-6 for α-, β- and γ- CD sensors, respectively. Interference was investigated by studying the selectivity coefficient values of the test sensors, which indicated that the methods were free from interference from investigated species. The determination of PR exhibited high recovery and favorable relative standard deviation using the investigated sensors. The sensors were subsequently used for the quantification of PR in a pharmaceutical formulation and the potentiometric results agreed with those of a spectrophotometric method. A molecular docking (MD) study was used to predict the structure of the inclusion complexes of PR (guest) and α- or β- or γ-CD (host). The study results indicated that the formed complexes were stable with sufficient binding energy.

Encapsulating curcumin in ethylene diamine-β-cyclodextrin nanoparticle improves topical cornea delivery

Curcumin is a powerful scavenger of reactive oxygen species and could prevent the corneal cells from oxidative damage. However, the clinical efficacy of curcumin is limited by its low aqueous solubility and stability, leading to poor bioavailability. β-cyclodextrin, with a hydrophilic surface and a hydrophobic cavity and self-assembling properties, can form inclusion complexes with lipophilic drugs such as curcumin for ocular delivery. We synthesized ethylene diamine (EDA)-modified β-cyclodextrin and prepared the curcumin complexation using the solvent evaporation method. The EDA-β-cyclodextrin provided a better thermodynamic stability and higher complex yield for curcumin complexes, compared to β-cyclodextrin, which were demonstrated on the analysis of their van't Hoff plots and phase solubility diagrams. We characterized EDA-β-cyclodextrin curcumin nanoparticles and determined that the EDA modified β-cyclodextrin is a more suitable carrier than parental β-cyclodextrin, using FT-IR, XRD, TEM, and analyses of solubility and storage stability. In addition, the curcumin-EDA-β-cyclodextrin nanoparticles had better in vitro corneal penetration and 3 -h cumulative flux in a porcine cornea experiment, and displayed an improved biocompatibility, confirmed by the histological examination of porcine corneas and cell viability of bovine corneal epithelial cells. These results together revealed a role of EDA modification in the β-cyclodextrin carrier, including the improvement of curcumin complex formation, thermodynamic properties, cytotoxicity, and the in vitro corneal penetration. The EDA-β-cyclodextrin inclusion can provide curcumin a higher degree of aqueous solubility and corneal permeability.

Physicochemical Profiling of Baicalin Along with the Development and Characterization of Cyclodextrin Inclusion Complexes

Baicalin is a flavone glycoside extracted from Scutellaria baicalensis, a traditional Chinese herbal medicine. Numerous pharmacological effects of baicalin were reported (e.g. antioxidant, anxiolytic); nevertheless, the most important physicochemical properties influencing the pharmacokinetic behaviour and the concomitant oral bioavailability have not yet been described in a comprehensive study. The aim of this project was to characterize the acid-base, lipophilicity, biorelevant solubility and permeability properties of the drug substance and providing scientific data to support the dosage form design. Another important objective was the comparative evaluation of six various baicalin-cyclodextrin (CD) inclusion complexes along with the creation of a suitable Drug Delivery System (DDS) for this BCS IV drug. Biorelevant profiling was carried out by NMR-pH titrations, saturation shake-flask and distribution coefficients (logP) measurements, while CD inclusion studies were fulfilled by experimental methods (phase solubility, ¹H/¹³C NMR, 2D ROESY) and computational approaches. Due to low aqueous solubility (67.03 ± 1.60 μg/ml) and low permeability (P_app = 0.037 × 10⁻⁶ cm/s), baicalin is classified as BCS IV. The γ-CD complexation significantly increased the solubility of baicalin (~ 5 times). The most promoted chemical shift change occurred in baicalin-γ-CD complex. Computational studies showed disparate binding pattern for baicalin in case of β- and γ-CD; furthermore, the calculated complexation energy was − 162.4 kJ mol⁻¹ for β-CD, while it was significantly stronger for γ-CD (− 181.5 kJ mol⁻¹). The physicochemical and structural information of baicalin and its CD complexes introduced herein can create molecular basis for a promising DDS with enhanced bioavailability containing a bioactive phytopharmacon.

[6]-Shogaol/β-CDs inclusion complex: preparation, characterisation, in vivo pharmacokinetics, and in situ intestinal perfusion study

Aims: The aim was to improve the absorption and bioavailability of [6]-shogaol with β-cyclodextrin (β-CD) prior to in vitro and in vivo evaluation. Methods: [6]-Shogaol/β-CDs inclusion complexes (6-S-β-CDs) were developed using saturated aqueous solution method and characterised with appropriate techniques. The absorption and bioavailability potential of [6]-shogaol was evaluated via in vivo pharmacokinetics and in situ intestinal perfusion. Results: The results of characterisation showed that 6-S-β-CDs (drug loading, 7.15%) were successfully formulated. In vitro release study indicated significantly improved [6]-shogaol release. Pharmacokinetic parameters such as Cmax, AUC0-36 h, and oral relative bioavailability (about 685.36%) were substantially enhanced. The in situ intestinal perfusion study revealed that [6]-shogaol was markedly absorbed via passive diffusion in the intestinal segments, and duodenum followed by ileum and jejunum. Conclusions: Cyclodextrin inclusion technology could enhance the intestinal absorption and oral bioavailability of hydrophobic drugs like [6]-shogaol.

Pharmacokinetics and Bioavailability Enhancement of Baicalin: A Review

Baicalin is one of the major bioactive components of Scutellaria radix, a Chinese herb that has been used since ancient times. Baicalin has various pharmacological activities, including antitumor, antimicrobial, and antioxidant, and has wide clinical applications. Baicalin displays a distinct pharmacokinetic profile including gastrointestinal hydrolysis, enterohepatic recycling, carrier-mediated transport, and complicated metabolism. The in vivo disposition of baicalin is affected by combinations of other herbs and baicalin can interact with other co-administered drugs due to competition between metabolic enzymes and protein binding. Furthermore, baicalin exhibits altered pharmacokinetic properties under different pathological conditions. Due to its low bioavailability, emerging novel baicalin preparations including nano/micro-scale baicalin delivery systems show better absorption and higher bioavailability in preclinical studies, and show promise for future clinical applications. Thus, this current review offers a comprehensive report on the pharmacokinetic behavior of baicalin and strategies to improve its bioavailability.

Development of morin/hydroxypropyl-β-cyclodextrin inclusion complex: Enhancement of bioavailability, antihyperalgesic and anti-inflammatory effects

Morin is a flavonoid has been reported with several pharmacological effects such as, antioxidant, anti-inflammatory, anticancer, antidiabetic, etc. However, morin has low solubility in water, which decreases the bioavailability and limits its clinical application. In this way, to improve the pharmaceutical properties, morin was complexed in hydroxypropyl-β-cyclodextrin (HP-β-CD) and its oral bioavailability and anti-inflammatory effects were evaluated. Initially, a phase solubility study was performed, which showed that HP-β-CD would be the better cyclodextrin for the formation of complexes with morin. The morin/HP-β-CD inclusion complex (1:1) was prepared by freeze-drying method. The sample obtained was characterized by DSC, FTIR, PXRD, SEM and ¹H NMR techniques, evidencing the formation of morin/HP-β-CD inclusion complex. In addition, complexation efficiency (98.3%) and loading content (17.63%), determined by HPLC demonstrated that morin was efficiently complexed in HP-β-CD. In vitro dissolution study confirmed that morin/HP-β-CD inclusion complex increased the solubility and dissolution rate of morin. The oral bioavailability of the morin/HP-β-CD complex and free morin were evaluated through a pharmacokinetic study in rat plasma. The oral bioavailability of morin complexed with HP-β-CD was increased by 4.20 times compared with the free morin. Hyperalgesia induced by carrageenan and carrageenan-induced pleurisy were carried out in mice to evaluate the antihyperalgesic and anti-inflammatory activities of free morin and inclusion complex. Morin/HP-β-CD inclusion complex showed antihyperalgesic effect in inflammatory pain model and anti-inflammatory effect decreasing leukocyte migration and TNF-α levels at a lower dose than free morin. Therefore, the morin/HP-β-CD inclusion complex improved the solubility, dissolution rate, oral bioavailability, antihyperalgesic and anti-inflammatory effects of morin. In this way, the morin/HP-β-CD inclusion complex exhibits potential for development of new pharmaceutical product for future clinical applications.

Optimization of Quality Attributes and Atomic Force Microscopy Imaging of Reconstituted Nanodroplets in Baicalin Loaded Self-Nanoemulsifying Formulations

The objective of the study was to develop baicalin loaded liquid self-nanoemulsifying drug delivery systems (BSNEDDS) and to characterize them by physicochemical methods in order to optimize the composition and quality attributes. Atomic force microscopy (AFM) was utilized to evaluate the morphological characteristics and size distribution of reconstituted nanoemulsion droplets with a new sample preparation method for the elucidation of individual nanodroplets without any signs of coalescence. Response surface methodology and desirability approach was used to select the optimized composition related to droplet size, zeta-potential, polydispersity index (PDI), and turbidity characteristics. Droplet size distribution measured by dynamic light scattering method was highly desirable with 52.87 ± 0.5322 nm, which was confirmed by AFM imaging. The optimized formula contains Peceol^® (14.29%, w/w), Kolliphor^® EL (57.14%, w/w), and Transcutol^® P (28.57%, w/w). Long-term stability analysis did not show any significant change in droplet size or PDI over the investigated period. More than 40.5-times solubility improvement was achieved with the optimized BSNEDDS correlated to solubility of baicalin in distilled water. In vitro dissolution studies at pH 1.2 and pH 6.8 were performed and revealed that the optimized BSNEDDS formula showed pH independent drug dissolution, and 100% of incorporated baicalin dissolved within five minutes in rapidly dispersing nanodroplets.

Labrasol-Enriched Nanoliposomal Formulation: Novel Approach to Improve Oral Absorption of Water-Insoluble Drug, Carvedilol

The purpose of the current study was to develop a novel liposomal formulation to improve the oral bioavailability of carvedilol, a Biopharmaceutics Classification System class II with poor aqueous solubility and extensive presystemic metabolism. Conventional and various surfactant-enriched carvedilol-loaded liposomes were prepared by thin film hydration technique and physicochemical properties of liposomes (including size, encapsulation efficiency, release behavior, and morphology) were evaluated. To assess the oral bioavailability, in vivo studies were carried out in eight groups of male Wistar rats (n = 6) and the drug plasma concentration was determined. Conventional and surfactant containing liposomes showed average particle size of 76-104 nm with a narrow size distribution, high encapsulation efficiency (80%≤) and a sustained release profile in simulated intestinal fluid. Compared to the suspension, conventional and Labrasol containing liposomes significantly improved the oral bioavailability and peak plasma concentration of carvedilol. Biocompatibility studies (cell cytotoxicity and histopathological analyses) showed that the enhancing effect might be achieved without any apparent toxicity in the intestine. Decreased oral absorption of carvedilol nanovesicles by using a chylomicron flow blocker indicated contribution of lymphatic transport in nanocapsules absorption. The results reported the successful development of biocompatible Labrasol-enriched carvedilol nanoliposomal formulation with a significant oral enhancement capability. Graphical Abstract ᅟ.

Thermogelling Platform for Baicalin Delivery for Versatile Biomedical Applications

Baicalin (BG) is a natural glycoside with several promising therapeutic and preventive applications. However, its pharmaceutical potential is compromised by its poor water solubility, complex oral absorption kinetics, and low bioavailability. In this work, BG was incorporated in a series of chitosan (Ch)/glycerophosphate (GP)-based thermosensitive hydrogel formulations to improve its water solubility and control its release profile. Molecular interactions between BG and GP were investigated using Fourier transform infrared spectroscopy (FT-IR), and the ability of GP to enhance the water solubility of BG was studied in different release media. Drug-loaded Ch/GP hydrogels were prepared and characterized for their gelation time, swelling ratio, and rheological properties in addition to surface and internal microstructure. Polyethylene glycol (PEG) 6000 and hydroxypropyl methyl cellulose (HPMC) were incorporated in the formulations at different ratios to study their effect on modulating the sol-gel behavior and the in vitro drug release. In vivo pharmacokinetic (PK) studies were carried out using a rabbit model to study the ability of drug-loaded Ch/GP thermosensitive hydrogels to control the absorption rate and improve the bioavailability of BG. Results showed that the solubility of BG was enhanced in the presence of GP, while the incorporation of PEG and/or HPMC had an impact on gelation time, rheological behavior, and rate of drug release in vitro. PK results obtained following buccal application of drug-loaded Ch/GP thermosensitive hydrogels to rabbits showed that the rate of BG absorption was controlled and the in vivo bioavailability was increased by 330% relative to BG aqueous oral suspension. The proposed Ch/GP thermosensitive hydrogel is an easily modifiable delivery platform that is not only capable of improving the solubility and bioavailability of BG following buccal administration but also can be suited for various local and injectable therapeutic applications.

Cyclodextrin Enhances Corneal Tolerability and Reduces Ocular Toxicity Caused by Diclofenac

With advances in refractive surgery and demand for cataract removal and lens replacement, the ocular use of nonsteroidal anti-inflammatory drugs (NSAIDs) has increased. One of the most commonly used NSAIDs is diclofenac (Diclo). In this study, cyclodextrins (CDs), α-, β-, γ-, and HP-β-CDs, were investigated with in vitro irritation and in vivo ulceration models in rabbits to reduce Diclo toxicity. Diclo-, α-, β-, γ-, and HP-β-CD inclusion complexes were prepared and characterized and Diclo-CD complexes were evaluated for corneal permeation, red blood cell (RBCs) haemolysis, corneal opacity/permeability, and toxicity. Guest- (Diclo-) host (CD) solid inclusion complexes were formed only with β-, γ-, and HP-β-CDs. Amphipathic properties for Diclo were recorded and this surfactant-like functionality might contribute to the unwanted effects of Diclo on the surface of the eye. Contact angle and spreading coefficients were used to assess Diclo-CDs in solution. Reduction of ocular toxicity 3-fold to16-fold and comparable corneal permeability to free Diclo were recorded only with Diclo-γ-CD and Diclo-HP-β-CD complexes. These two complexes showed faster healing rates without scar formation compared with exposure to the Diclo solution and to untreated groups. This study also highlighted that Diclo-γ-CD and Diclo-HP-β-CD demonstrated fast healing without scar formation.

Comparison of a revaprazan-loaded solid dispersion, solid SNEDDS and inclusion compound: Physicochemical characterisation and pharmacokinetics

The aim of this research was to compare three strategies for enhancing the solubility of poorly water-soluble revaprazan hydrochloride: solid dispersion, solid SNEDDS and inclusion compound. The influence of polymers, surfactants and oils on the drug solubility was assessed, and via the chosen carriers, the three types of formulations were prepared utilising spray drying technique. Their physicochemical properties, solubility, dissolution and pharmacokinetics in rats were performed compared with revaprazan powder. Among the liquid SNEDDS formulations assessed, the compositions of revaprazan, peceol, Tween 80 and Labrasol (10:15:55:30, weight ratio) provided the smallest emulsion size. Moreover, this liquid SNEDDS and dextran were suspended/dissolved in distilled water, and spray-dried, producing an optimal revaprazan-loaded solid SNEDDS. The appropriate solid dispersion and inclusion compound were composed of revaprazan, hydroxypropylmethylcellulose and cremophor A25 (5:1.4:5.6) and drug and hydroxyl-β-cyclodextrin (2.5:8.77), respectively. The crystalline drug was converted to an amorphous state in all formulations. In the solid dispersion, the drug was attached to the hydrophilic carrier. The solid SNEDDS and inclusion compound contained aggregate microspheres and separate microspheres, respectively. All formulations significantly increased the drug solubility, dissolution, plasma concentration and AUC compared with revaprazan powder. These properties were ranked in the order solid dispersion ≥ solid SNEDDS > inclusion compound. Particularly, the solid dispersion improved about 9500-fold drug solubility and 10-fold oral bioavailability. Thus, the improved properties were considerably dependent upon these techniques, although all of the techniques employed similar mechanisms. Among the strategies checked, the solid dispersion system would be recommended as an oral revaprazan-loaded pharmaceutical product.

Encapsulation Mechanism of Oxyresveratrol by β-Cyclodextrin and Hydroxypropyl-β-Cyclodextrin and Computational Analysis

In this study, the encapsulation mechanism of oxyresveratrol and β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) was studied. As this research shows, oxyresveratrol and two cyclodextrins (CDs) were able to form inclusion complexes in a 1:1 stoichiometry. However, the interaction with HP-β-CD was more efficient, showing up as higher encapsulation constant (K_F) (35,864.72 ± 3415.89 M⁻¹). The K_F values exhibited a strong dependence on temperature and pH, which decreased as they increased. From the thermodynamic parameters (ΔH⁰, ΔS⁰, and ΔG⁰) of the oxyresveratrol loaded β-CD (oxyresveratrol-β-CD) and HP-β-CD (oxyresveratrol-HP-β-CD), it could be seen that the complexation process was spontaneous and exothermic, and the main driving forces between oxyrsveratrol and CDs were hydrogen bonding and van der waals force. Besides, molecular docking combined with ¹H-NMR were used to explain the most possible mode of interactions between oxyresveratrol and CDs.