Characterization of the Supermolecular Structure of Polydatin/6-O-α-Maltosyl-β-cyclodextrin Inclusion Complex

Thermal Characterization and Heat Capacities of Seven Polyphenols

Polyphenolic compounds are key elements in sectors such as pharmaceutics, cosmetics and food; thus, their physicochemical characterization is a vital task. In this work, the thermal behavior of seven polyphenols (trans-resveratrol, trans-polydatin, kaempferol, quercetin, myricetin, hesperidin, and (-)-epicatechin) was investigated with DSC (differential scanning calorimetry) and TGA (thermogravimetric analysis). Melting temperatures, enthalpies of fusion and decomposition temperatures were determined, and heat capacities were measured in the temperature range from 283.15 K to 363.15 K. Results were compared to the scarce experimental data available in the literature, showing a satisfactory agreement. All compounds were found to be thermally stable until melting, upon which they rapidly decomposed. Myricetin was the only polyphenol that presented polymorphic behavior, exhibiting two phase transitions prior to melting. Heat capacities increased minimally with temperature in the studied range. In addition, the group contribution method developed by Marrero and Gani was used to estimate the thermal properties of the polyphenols, achieving high accuracy for melting temperatures.

Synergetic Effect of β-Cyclodextrin and Its Simple Carbohydrate Substituents on Complexation of Folic Acid and Its Structural Analog Methotrexate

Folic acid (FA) and its structural analog, anticancer medicine methotrexate (MTX), are known to form host/guest complexes with native cyclodextrins, of which the most stable are formed with the medium-sized β-cyclodextrin. Based on our research, proving that simple sugars (D-glucose, D-galactose, and D-mannose) can form adducts with folic acid, we envisioned that combining these two types of molecular receptors (cyclodextrin and simple carbohydrates) into one may be beneficial for the complexation of FA and MTX. We designed and obtained host/guest inclusion complexes of FA and MTX with two monoderivatives of β-cyclodextrin-substituted at position 6 with monosaccharide (glucose, G-β-CD) and disaccharide (maltose, Ma-β-CD). The complexation was proved by experimental (NMR, UV-vis, IR, TG, DSC) and theoretical methods. We proved that derivatization of β-cyclodextrin with glucose and maltose has a significant impact on the complexation with FA and MTX, as the addition of one glucose subunit to the structure of the receptor significantly increases the value of association constant for both FA/G-β-CD and MTX/G-β-CD, while further extending a pendant chain (incorporation of maltose subunit) results in no additional changes.

Interaction mechanism of okra (Abelmoschus esculentus L.) seed protein and flavonoids: Fluorescent and 3D-QSAR studies

The binding capacity of 10 flavonoids with okra seed protein (OSP) was studied by fluorescence spectroscopy. The structure of flavonoids had an obvious impact on binding performance. The binding ability of flavanone was lower than that of flavone, isoflavone and dihydrochalcone. The binding capacity of flavonoid glycoside was superior to that of the corresponding flavonoid aglycone. The binding ability was positively correlated with the number of phenolic hydroxyl groups on the B ring. The steric field and electrostatic field model constructed by 3D-QSAR method could well explain the above interaction behavior. Thermodynamic analysis suggested that the quenching mechanism of OSP caused by flavonoids was static quenching, and the binding-site number was 1. In addition, hydrogen bonding and van der Waals force dominated this interaction. The 3D and synchronous fluorescence spectra showed that there was no significant change in the polarity of the environment around tryptophan and tyrosine residues during binding.

Dispersion-corrected DFT calculations and umbrella sampling simulations to investigate stability of Chrysin-cyclodextrin inclusion complexes

The study of inclusion complexes of Chrysin (ChR) with three forms of cyclodextrins (CDs) α-, β-, and γ-CD was accomplished to examine the stability of ChR inside the central cavities of CDs. The aim of study was to identify the most suitable form of CD to improve the hydro-solubility of poorly soluble ChR bioactive molecule. Microsecond timescale molecular dynamics (MD) simulations were performed on four inclusion complexes (α-CD/ChR, β-CD/ChR, and two conformations of γ-CD/ChR) to examine the dynamics of ChR inside the cavity of CDs. The first conformation of γ-CD/ChR inclusion complex (γ-CD1/ChR) was identified to possess the highest affinity between host and guest molecule on the basis of binding energy calculated by employing Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) and umbrella sampling simulations. To further strengthen the claims of classical and biased MD studies, Our own N-layered Integrated molecular Orbital and Molecular mechanics (ONIOM) (wB97XD/6-311+g(d,p):pm7) calculations were performed on the selected inclusion complexes. The ONIOM based complexation energy reaffirmed that ChR had highest affinity for the γ-CD1 host molecule. Further, the non-covalent interaction analysis was conducted using Multiwfn software on QM-optimized inclusion complexes with wB97XD/6-311+G(d,p) model chemistry, revealing non-covalent interactions between ChR and CDs. This atomic level information helped us to gain better insights into critical atoms of ChR and CD that participated in intermolecular interactions and identify γ-CD as a suitable host molecule for improving the hydro-solubulity of ChR. The structural insights would help to derive new derivatives of γ-CD with better host capacity.

Co-Crystals of Resveratrol and Polydatin with L-Proline: Crystal Structures, Dissolution Properties, and In Vitro Cytotoxicities

Resveratrol (RSV) and polydatin (PD) have been widely used to treat several chronic diseases, such as atherosclerosis, pulmonary fibrosis, and diabetes, among several others. However, their low solubility hinders their further applications. In this work, we show that the solubility of PD can be boosted via its co-crystallization with L-proline (L-Pro). Two different phases of co-crystals, namely the RSV-L-Pro (RSV:L-Pro = 1:2) and PD-L-Pro (PD:L-Pro = 1: 3), have been prepared and characterized. As compared to the pristine RSV and PD, the solubility and dissolution rates of PD-L-Pro in water (pH 7.0) exhibited a 15.8% increase, whereas those of RSV-L-Pro exhibited a 13.8% decrease. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay of pristine RSV, PD, RSV-L-Pro, and PD-L-Pro against lung cancer cell line A549 and human embryonic kidney cell line HEK-293 indicated that both compounds showed obvious cytotoxicity against A549, but significantly reduced cytotoxicity against HEK-293, with PD/PD-L-Pro further exhibiting better biological safety than that of RSV/RSV-L-Pro. This work demonstrated that the readily available and biocompatible L-Pro can be a promising adjuvant to optimize the physical and chemical properties of RSV and PD to improve their pharmacokinetics.

A comparative study of photoresponsive molecularly imprinted polymers with different shell thicknesses: Effects on 6-O-α-maltosyl-β-cyclodextrin separation

Photoresponsive surface molecularly imprinted polymers (PSMIPs) with controlled nanoshell thicknesses were synthesized using different amounts of precursor materials to determine the effects of polymer shell layer thickness on the separation and purification of 6-O-alpha-maltosyl-beta-cyclodextrin (Mal-β-CD). The physicochemical properties and adsorption and desorption capacities of PSMIPs with different shell thicknesses were studied. Interestingly, the uniform thickness of the imprinted polymer shell layer could be adjusted from 10 to 60 nm by varying the amount of polymerization precursors, and the average mesopore diameter of PSMIPs was not significantly affected by shell thickness. However, the removal efficiency and selective capacity of PSMIPs on Mal-β-CD were strongly correlated to their shell thickness. The adsorption behavior of PSMIPs on Mal-β-CD fitted well with the Langmuir adsorption model and pseudo-second-order kinetic model. Based on the obtained results, PSMIPs with a 30-nm imprinted layer were found to be an excellent adsorbent for Mal-β-CD separation, with an adsorption capacity of 18.12 mg/g. They can therefore be used for industrial chromatographic separations of Mal-β-CD in the future. PRACTICAL APPLICATION: This article clearly demonstrated that the shell thickness of core-shell molecularly imprinted materials affected the degree and rate of cyclodextrin separation. Determining the optimal thickness is of great significance for the material in the separation and purification of cyclodextrin.

Encapsulation mechanism of α-mangostin by β-cyclodextrin: Methods of molecular docking and molecular dynamics

The study aimed to investigate the interaction of host-guest between α-mangostin and β-cyclodextrin (βCD) and also to calculate the energy of the complex system between α-mangostin with βCD for drug delivery using methods of 15 molecular dynamics and molecular docking. Simulation of molecular docking and molecular dynamics was utilized to determine molecular interactions and the complex system's bond energy. The docking simulation results showed that α-mangostin-βCD complex has a Gibbs energy value (ΔG) of -6.69 kcal/mol. The Gibbs energy value (ΔG) of molecular dynamics simulation from MMGBSA calculation showed the binding energy of α-mangostin-βCD - 11.73 kcal/mol.

Polydatin Encapsulated Poly [Lactic-co-glycolic acid] Nanoformulation Counteract the 7,12-Dimethylbenz[a] Anthracene Mediated Experimental Carcinogenesis through the Inhibition of Cell Proliferation

In the present study, the authors have attempted to fabricate Polydatin encapsulated Poly [lactic-co-glycolic acid] (POL-PLGA-NPs) to counteract 7,12-dimethyl benzyl anthracene (DMBA) promoted buccal pouch carcinogenesis in experimental animals. The bio-formulated POL-PLGA-NPs were characterized by dynamic light scattering (DLS), Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD) pattern analysis, and transmission electron microscope (TEM). In addition, the nano-chemopreventive potential of POL-PLGA-NPs was assessed by scrutinizing the neoplastic incidence and analyzing the status of lipid peroxidation, antioxidants, phase I, phase II detoxification status, and histopathological changes and in DMBA-treated animals. In golden Syrian hamsters, oral squamous cell carcinoma (OSCC) was generated by painting with 0.5% DMBA in liquid paraffin three times a week for 14 weeks. After 100% tumor formation was observed, high tumor volume, tumor burden, and altered levels of biochemical status were observed in the DMBA-painted hamsters. Intra-gastric administration of varying concentration of POL-PLGA-NPs (7.5, 15, and 30 mg/kg b.wt) to DMBA-treated hamsters assumedly prevents oncological incidences and restores the status of the biochemical markers. It also significantly enhances the apoptotic associated and inhibits the cancer cell proliferative markers expression (p53, Bax, Bcl-2, cleaved caspase 3, cyclin-D1). The present study reveals that POL-PLGA-NPs is a penitential candidate for nano-chemopreventive, anti-lipid peroxidative, and antioxidant potential, and also has a modulating effect on the phase I and Phase II detoxification system, which is associated with reduced cell proliferation and induced apoptosis in experimental oral carcinogenesis.

Cyclodextrin/chitosan nanoparticles for oral ovalbumin delivery: Preparation, characterization and intestinal mucosal immunity in mice

A novel oral protein delivery system with enhanced intestinal penetration and improved antigen stability based on chitosan (CS) nanoparticles and antigen-cyclodextrin (CD) inclusion complex was prepared by a precipitation/coacervation method. Ovalbumin (OVA) as a model antigen was firstly encapsulated by cyclodextrin, either β-cyclodextrin (β-CD) or carboxymethyl-hydroxypropyl-β-cyclodextrin (CM-HP-β-CD) and formed OVA-CD inclusion complexes, which were then loaded to chitosan nanoparticles to form OVA loaded β-CD/CS or CM-HP-β-CD/CS nanoparticles with uniform particle size (836.3 and 779.2 nm, respectively) and improved OVA loading efficiency (27.6% and 20.4%, respectively). In vitro drug release studies mimicking oral delivery condition of OVA loaded CD/CS nanoparticles showed low initial releases at pH 1.2 for 2 h less than 3.0% and a delayed release which was below to 30% at pH 6.8 for further 72 h. More importantly, after oral administration of OVA loaded β-CD/CS nanoparticles to Balb/c mice, OVA-specific sIgA levels in jejunum of OVA loaded β-CD/CS nanoparticles were 3.6-fold and 1.9-fold higher than that of OVA solution and OVA loaded chitosan nanoparticles, respectively. In vivo evaluation results showed that OVA loaded CD/CS nanoparticles could enhance its efficacy for inducing intestinal mucosal immune response. In conclusion, our data suggested that CD/CS nanoparticles could serve as a promising antigen-delivery system for oral vaccination.

Photostability and antioxidant activity studies on the inclusion complexes of trans-polydatin with β-cyclodextrin and derivatives

The inclusion complexes of trans-polydatin and three cyclodextrins (CDs), namely β-cyclodextrin (β-CD), methyl-β-cyclodextrin (Me-β-CD) and (2-hydroxy) propyl-β-cyclodextrin (HP-β-CD) were prepared.