Theoretical and Experimental Studies on Inclusion Complexes of Pinostrobin and β-Cyclodextrins

β-Cyclodextrin mediated controlled release of phenothiazine from pH-responsive pectin and pullulan-based hydrogel optimized through experimental design

Drugs with lower permeability and water solubility provide major challenges for producing safe and efficient formulations. The current work aims to prepare ICs of the drug phenothiazine and β-cyclodextrin via physical, microwave, freeze-drying, and kneading methods. Many analytical methods, such as 1H NMR, ROESY, FT-IR, DSC, SEM, and XRD, were then used to confirm the formation of inclusion complexes. The natural polysaccharide-based hydrogel comprising pectin and pullulan was synthesized in air and optimized through various parameters. In order to maximize the reaction parameters, Response Surface Methodology design was employed for experimental optimization. We use FT-IR, TGA, SEM, EDX, and XRD to investigate hydrogel formation. At 37 °C, an investigation was carried out on the in vitro controlled release of PN at pH 2, 7, and 7.4. The analysis of drug release data revealed that PM and KM exhibited an initial burst release of drugs, with the MW and FD method proving to be the most suitable approach for achieving precise ICs of PN and β-CD for sustained drug release. The kinetics of drug release were evaluated using various kinetic models, with the Riteger-Peppas and Peppas-Sahlin models demonstrating the best fit for drug release in all instances.

The Solubility Studies and the Complexation Mechanism Investigations of Biologically Active Spiro[cyclopropane-1,3'-oxindoles] with β-Cyclodextrins

In this work, we first improved the aqueous solubility of biologically active spiro[cyclopropane-1,3′-oxindoles] (SCOs) via their complexation with different β-cyclodextrins (β-CDs) and proposed a possible mechanism of the complex formation. β-CDs significantly increased the water solubility of SCOs (up to fourfold). Moreover, the nature of the substituents in the β-CDs influenced the solubility of the guest molecule (MβCD > SBEβCD > HPβCD). Complexation preferably occurred via the inclusion of aromatic moieties of SCOs into the hydrophobic cavity of β-CDs by the numerous van der Waals contacts and formed stable supramolecular systems. The phase solubility technique and optical microscopy were used to determine the dissociation constants of the complexes (Kc~102 M−1) and reveal a significant decrease in the size of the formed crystals. FTIR-ATR microscopy, PXRD, and 1H-1H ROESY NMR measurements, as well as molecular modeling studies, were carried out to elucidate the host−guest interaction mechanism of the complexation. Additionally, in vitro experiments were carried out and revealed enhancements in the antibacterial activity of SCOs due to their complexation with β-CDs.

Cyclodextrins and Their Polymers Affect the Lipid Membrane Permeability and Increase Levofloxacin’s Antibacterial Activity In Vitro

Cyclodextrins (CDs) are promising drug carriers that are used in medicine. We chose CDs with different substituents (polar/apolar, charged/neutral) to obtain polymers (CDpols) with different properties. CDpols are urethanes with average Mw of ~120 kDa; they form nanoparticles 100–150 nm in diameter with variable ζ-potential. We studied the interaction of CD and CDpols with model (liposomal) and bacterial membranes. Both types of CD carriers cause an increase in the liposomal membrane permeability, and for polymers, this effect was almost two times stronger. The formation of CD/CDpols complexes with levofloxacin (LV) enhances LV’s antibacterial action 2-fold in vitro on five bacterial strains. The most pronounced effect was determined for LV-CD complexes. LV-CDs and LV-CDpols adsorb on bacteria, and cell morphology influences this process dramatically. According to TEM studies, the rough surface and proteinaceous fimbria of Gram-negative E. coli facilitate the adsorption of CD particles, whereas the smooth surface of Gram-positive bacteria impedes it. In comparison with LV-CDs, LV-CDpols are adsorbed 15% more effectively by E. coli, 2.3-fold better by lactobacilli and 5-fold better in the case of B. subtilis. CDs and CDpols are not toxic for bacterial cells, but may cause mild defects that, in addition to LV-CD carrier adsorption, improve LV’s antibacterial properties.

Study of the dermal anti-inflammatory, antioxidant, and analgesic activity of pinostrobin

Pinostrobin is a flavanone isolated from Renealmia alpinia (Rottb.) Maas, which is used to treat painful diseases and ailments; indigenous peoples use it as plasters. Different plant species have been reported as a source of this flavonoid, among which are: Boesenbergia rotunda, Cajanus cajan, Piper ecuadorense, Piper hispidum, Teloxys graveolens, Kaempferia pandurata, among others.

Pinostrobin expresses potentially useful biological activities such as antioxidant, analgesic, and dermal anti-inflammatory, at low levels nonetheless due to its low solubility. The formation of inclusion complexes deems a good strategy to improve the pharmacologic effects of many substances.

In the present work, we evaluated the dermal toxicity, analgesic and dermal anti-inflammatory activity of pinostrobin included in cyclodextrins, to improve those effects on experimental animals. To include pinostrobin, we used two of beta cyclodextrin (βCD) and hydroxypropil beta cyclodextrin (HPβCD) complexes using two methods developed by Benesi-Hildebrand and Higuchi-Connors. Dermal anti-inflammatory activity was evaluated in experimental mice by inhibiting the edema generated by 12-O-tetradecanoylforbol-13-acetate (TPA). Analgesic activity was evaluated by inducing chemical pain by means of a Siegmund test. Antioxidant activities were measured with two in vitro tests.

Analgesic and dermal anti-inflammatory activities of pinostrobin, as included in control and experimental complexes, showed comparatively better effects than pinostrobin without inclusion complexes. Our results indicate that both beta cyclodextrin (βCD) and hydroxypropyl beta cyclodextrin (HPβCD) enhance the different effects of pinostrobin, which may indicate greater bioavailability.

Aurisin A Complexed with 2,6-Di-O-methyl-β-cyclodextrin Enhances Aqueous Solubility, Thermal Stability, and Antiproliferative Activity against Lung Cancer Cells

Aurisin A (AA), an aristolane dimer sesquiterpene isolated from the luminescent mushroom Neonothopanus nambi, exhibits various biological and pharmacological effects. However, its poor solubility limits its use for further medicinal applications. This study aimed to improve the water solubility of AA via complexation with β-cyclodextrin (βCD) and its derivatives (2,6-di-O-methyl-βCD (DMβCD) and 2-hydroxypropyl-βCD (HPβCD). A phase solubility analysis demonstrated that the solubility of AA linearly enhanced with increasing concentrations of βCDs (ranked in the order of AA/DMβCD > AA/HPβCD > AA/βCD). Notably, βCDs, especially DMβCD, increased the thermal stability of the inclusion complexes. The thermodynamic study indicated that the complexation between AA and βCD(s) was a spontaneous endothermic reaction, and AA/DMβCD possesses the highest binding strength. The complex formation between AA and DMβCD was confirmed by means of FT-IR, DSC, and SEM. Molecular dynamics simulations revealed that the stability and compactness of the AA/DMβCD complex were higher than those of the DMβCD alone. The encapsulation of AA led to increased intramolecular H-bond formations on the wider rim of DMβCD, enhancing the complex stability. The antiproliferative activity of AA against A549 and H1975 lung cancer cells was significantly improved by complexation with DMβCD. Altogether, the satisfactory water solubility, high thermal stability, and enhanced antitumor potential of the AA/DMβCD inclusion complex would be useful for its application as healthcare products or herbal medicines.

Sustained release of edaravone from (2-hydroxypropyl)-β-cyclodextrin mediated tamarind kernel powder/kappa-carrageenan hydrogel: Microwave-assisted synthesis and optimization using experimental design

In the current study, a sustained release formulation made of natural polysaccharide tamarind kernel powder/kappa-carrageenan and (2-hydroxypropyl)-β-cyclodextrin (2-Hp-β-CD) was chosen to increase drug effectiveness. A kappa-carrageenan and tamarind kernel powder 3-D hydrogel network was synthesized with the aid of microwave irradiations. The ICs complexes were prepared using a physical mixture (PM), kneading (KM), and microwave (MW) approach and were then successfully loaded into the hydrogel. The synthesis of ICs was verified as a true IC using DSC, SEM, FTIR, ¹H NMR, and 2D NMR ROESY. A study on the in vitro sustained release of EV at pH 2, 7, and 7.4 was conducted at 37 °C. The microwave (MW) method was the most effective method for preparing true ICs of EV and 2-Hp-β-CD for sustained drug release, as evidenced by the drug release data, which indicated that PM and KM displayed a burst release of the drug. Ritger-Peppas and Peppas-Sahlin were essential models for drug release. A phase solubility analysis was done to evaluate the IC's stoichiometry and complexation constant. Studies on drug release have shown that 2-Hp-β-CD was effective at causing pH-responsive sustained drug release.

Comparative Evaluation for Controlled Release of Amoxicillin from RSM-CCD-Optimized Nanocomposites Based on Sodium Alginate and Chitosan-Containing Inclusion Complexes

Amoxicillin (AMX) is a semisynthetic antibiotic, an analogue of ampicillin, with a wide spectrum of bacterial activity against many microorganisms but possesses some limits. To increase the drug effectiveness, supramolecule nanocomposites composed of β-cyclodextrin (β-CD) and chitosan/sodium alginate/GO were chosen in the present study as a sustained release formulation. Nanocomposites of chitosan (CH), sodium alginate (ALG), and graphene oxide (GO) were synthesized at 50 °C. The inclusion complexes (ICs) were processed via the physical mixture (PM), kneading (KM), microwave (MW) method, or coprecipitation (CP) and directly loaded into the nanocomposite. To confirm the formation of true ICs, the ICs were analyzed by DSC, SEM, ¹H NMR, 2D NMR ROESY, and XRD. A drug release study was performed to find out which method is best for the controlled release of drugs in different environments of pH 2, 7, and 7.4 at 37 °C. From the observed drug release data, it was found that PM and KM showed a burst release of drugs and the microwave method was the most suitable method to prepare exact ICs of AMX and β-CD for sustained release of drugs. Kinetics of drug release was analyzed by various kinetic models, and it was observed that the Korsmeyer-Peppas and Peppas-Sahlin models were best fit for drug release in all cases. A Phase solubility study was carried out to find the stoichiometry of IC formation and the complexation constant. The drug release was controlled and pH-dependent, confirming that nanocomposites are pH-sensitive. From drug release analysis, it was acknowledged that β-CD is capable of causing sustained drug release.

Application of Molecular Dynamics Simulations in the Analysis of Cyclodextrin Complexes

Cyclodextrins (CDs) are highly respected for their ability to form inclusion complexes via host-guest noncovalent interactions and, thus, ensofance other molecular properties. Various molecular modeling methods have found their applications in the analysis of those complexes. However, as showed in this review, molecular dynamics (MD) simulations could provide the information unobtainable by any other means. It is therefore not surprising that published works on MD simulations used in this field have rapidly increased since the early 2010s. This review provides an overview of the successful applications of MD simulations in the studies on CD complexes. Information that is crucial for MD simulations, such as application of force fields, the length of the simulation, or solvent treatment method, are thoroughly discussed. Therefore, this work can serve as a guide to properly set up such calculations and analyze their results.

Enhanced Solubility and Anticancer Potential of Mansonone G By β-Cyclodextrin-Based Host-Guest Complexation: A Computational and Experimental Study

Mansonone G (MG), a plant-derived compound isolated from the heartwood of Mansonia gagei, possesses a potent antitumor effect on several kinds of malignancy. However, its poor solubility limits the use for practical applications. Beta-cyclodextrin (βCD), a cyclic oligosaccharide composed of seven (1→4)-linked α-D-glucopyranose units, is capable of encapsulating a variety of poorly soluble compounds into its hydrophobic interior. In this work, we aimed to enhance the water solubility and the anticancer activity of MG by complexation with βCD and its derivatives (2,6-di-O-methyl-βCD (DMβCD) and hydroxypropyl-βCD). The 90-ns molecular dynamics simulations and MM/GBSA-based binding free energy results suggested that DMβCD was the most preferential host molecule for MG inclusion complexation. The inclusion complex formation between MG and βCD(s) was confirmed by DSC and SEM techniques. Notably, the MG/βCDs inclusion complexes exerted significantly higher cytotoxic effect (~2–7 fold) on A549 lung cancer cells than the uncomplexed MG.

The modulatory effect and the mechanism of flavonoids on obesity

With the improvement of living standards, obesity has become a serious health problem all over the word. Currently, the methods and drugs for obesity treatment have some limitations and side effects. Flavonoids are active constituents with various biological activities, widely found in plants, and numerous studies have shown that flavonoids can inhibit obesity and related metabolism disorders effectively. This perspective reviews the recent progress in understanding the anti-obesity effects of flavonoids through modulating food intake, enzyme activities, nutrition absorption, adipogenesis and adipocyte lifecycle, thermogenesis, energy consumption, and intestinal microbiota. PRACTICAL APPLICATIONS: Natural bioactive substance flavonoids have anti-obesity property, which may play a role in anti-obesity drugs or functional food without any side effects. Flavonoids can inhibit weight gain directly or through their biologically active metabolites by various potential pathways. A better understanding of the modulatory effect and the mechanism of flavonoids on obesity will allow us to better utilize flavonoids in plants to treat obesity and related metabolic syndrome.

Nepafenac-Loaded Cyclodextrin/Polymer Nanoaggregates: A New Approach to Eye Drop Formulation

The topical administration route is commonly used for targeting therapeutics to the eye; however, improving the bioavailability of drugs applied directly to the eye remains a challenge. Different strategies have been studied to address this challenge. One of them is the use of aggregates that are formed easily by self-assembly of cyclodextrin (CD)/drug complexes in aqueous solution. The aim of this study was to design a new eye drop formulation based on aggregates formed between CD/drug complexes. For this purpose, the physicochemical properties of the aggregates associated with six CDs and selected water-soluble polymers were analysed. Complex formation was studied using differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR) and ¹H nuclear magnetic resonance spectroscopy (¹H-NMR). Results showed that HPβCD performed best in terms of solubilization, while γCD performed best in terms of enhancing nanoaggregate formation. Formation of inclusion complexes was confirmed by DSC, FT-IR and ¹H-NMR studies. A mixture of 15% (w/v) γCD and 8% (w/v) HPβCD was selected for formulation studies. It was concluded that formulations with aggregate sizes less than 1 µm and viscosity around 10–19 centipoises can be easily prepared using a mixture of CDs. Formulations containing polymeric drug/CD nanoaggregates represent an interesting strategy for enhanced topical delivery of nepafenac.

Pinostrobin Inhibits Proprotein Convertase Subtilisin/Kexin-type 9 (PCSK9) Gene Expression through the Modulation of FoxO3a Protein in HepG2 Cells

Pinostrobin, a flavonoid phytochemical found in variety of plants, has been demonstrated to possess numerous bioactivities such as antioxidant, anti-inflammatory, anticancer, and neuroprotective properties. The aim of this study was to investigate the hypocholesterolemic effect of pinostrobin on the regulation of the gene expression of PCSK9 and its underlying mechanisms in hepatic cells. We found that pinostrobin (20 and 40 μM) significantly inhibited the PCSK9 promoter activity from 1.00 ± 0.16 (fold) to 0.85 ± 0.06 and 0.54 ± 0.05, respectively, as well as the suppression of PCSK9 mRNA expression from 1.00 ± 0.11 (fold) to 0.81 ± 0.07 and 0.58 ± 0.07, respectively, in HepG2 cells. Pinostrobin significantly reduced the mature form of the PCSK9 protein, inhibited the catalytic activity of PCSK9, and increased the protein level of LDLR and the LDL uptake activity in HepG2 cells. We further demonstrated that pinostrobin markedly increased the level of nuclear forkhead box O3a (FoxO3a) protein, enhanced FoxO3a/PCSK9 promoter complexes formation, and attenuated the promoter binding capacity of nuclear HNF-1α. The knockdown of FoxO3a in HepG2 cells by small interference RNA (siRNA) abolished the pinostrobin-mediated PCSK9 reduction. Finally, we demonstrated that pinostrobin attenuated simvastatin-induced PCSK9 overexpression in HepG2 cells. Our current findings reveal that pinostrobin is a PCSK9 inhibitor and down-regulates the PCSK9 gene expression through the up-regulation of the FoxO3a level in hepatic cells. Pinostrobin with potential PCSK9 inhibitory activity may serve as a novel agent for cholesterol regulation and lipid management.