Phase-solubility Measurements Research Articles

Inclusion complexes of nabumetone with β-cyclodextrins: Spectroscopic, spectrometric and calorimetric studies in solution

The complexation of nabumetone (NAB) with various cyclodextrins (CDs): β-cyclodextrin (β-CD), hydroxypropyl-β-CD (HPβCD), randomly methylated β-CD (RMβCD), and sulfobutylether sodium salt β-CD (SBEβCD), was investigated as a mean to increase the poor solubility of NAB both in water and simulated biorelevant media (pH = 1.0 (HCl) and pH = 4.5 and 6.8 (phosphate buffer)). An approximately 170 times increase in NAB solubility was achieved for SBEβCD in all media. The formation of 1:1 complexes was confirmed by phase-solubility measurements, spectrofluorimetric titration and high resolution mass spectrometry. Additionally, isothermal microcalorimetric titrations were employed to determine thermodynamic parameters (lgK, ΔrG0, ΔrH0, ΔrS0). Stability constants (lgK = 3.42; 3.41; 3.47 and 3.62 for NAB complexes with β-CD, HPβCD, RMβCD, and SBEβCD, respectively) agree with those obtained by phase-solubility experiments and spectrofluorimetric titrations. The inclusion was enthalpy and entropy favorable. NMR analyses showed two possible orientations of NAB in the β-CD cavity simultaneously exist in the solution, with a naphthalene ring inside the β-CD cavity and methoxy or butanone substituent oriented towards the narrow β-CD rim. All experimental results are in good agreement with those based on molecular modeling previously reported in the literature.

Formulation of Ensulizole with Beta-Cyclodextrins for Improved Sunscreen Activity and Biocompatibility

In today's context, prolonged exposure to sunlight is widely recognized as a threat to human health, leading to a range of adverse consequences, including skin cancers, premature skin aging, and erythema. To mitigate these risks, preventive actions mainly focus on advocating the application of sunscreen lotions and minimizing direct exposure to sunlight. This research study specifically centered on ensulizole (ENS), a prominent ingredient in sunscreens. The objective was to create inclusion complexes (ICs) with Beta-cyclodextrin (B–CD) and its hydroxypropyl derivatives (H–CD). Using phase solubility measurements, we determined that both B–CD and H–CD form 1:1 stoichiometric ICs with ENS. Proton nuclear magnetic resonance spectral (1H NMR) analysis confirmed that the phenyl portion of ENS is encapsulated within the B–CD cavity. Significant changes in surface morphology were observed during the formation of these ICs compared to ENS and CDs alone. Quantum mechanical calculations were employed to further support the formation of ICs by providing energy data. Particularly, the photostability of the ENS:B–CD ICs remained intact for up to four hours of UV exposure, with no significant alterations in the structure of ENS. Furthermore, comprehensive biocompatibility assessments yielded encouraging results, suggesting the potential application of these inclusion complexes in cosmetics as a UVB sunscreen. In summary, our research underscores the successful creation of inclusion complexes characterized by enhanced photostability and safe biocompatibility.

Enhanced photostability and biocompatibility of sunscreen formulation of 2-phenylbenzimidazole-5-sulfonic acid with methyl-beta-cyclodextrin

Ensuring the photostability of sunscreen lotions is crucial for their effectiveness and safety when exposed to sunlight. Photostability refers to the ability of a substance to remain stable and undergo minimal chemical degradation or photochemical reactions upon exposure to ultraviolet (UV) radiation, especially from sunlight. In this study, we focused on 2-phenylbenzimidazole-5-sulfonic acid (PBS), one of the leading sunscreen agents, and aimed to form inclusion complexes (IC) with methyl-β-cyclodextrin (MCD). Through phase solubility measurements, we determined the stoichiometry of the IC to be 1:1, with a binding constant of 155.4 M−1. Proton Nuclear Magnetic Resonance (1H NMR) and ROESY analysis provided evidence that the benzimidazole part of PBS is successfully included in the cavity of MCD. Quantum mechanical calculations using the B3LYP/6-31G(D, P) method in the Gaussian 16 package further supported the formation of the IC by providing energy data. Notably, the photostability of the IC is maintained for up to four hours of UV exposure, showing no significant structural changes in PBS. Moreover, we conducted biocompatibility tests, and the results are encouraging for the superior activity, and suggest the potential of the IC for promoting its cosmetic application as a UVB sunscreen.

Structural Investigation of Hesperetin-7-O-Glucoside Inclusion Complex with β-Cyclodextrin: A Spectroscopic Assessment

Flavonoids are biologically active natural products of great interest for their potential applications in functional foods and pharmaceuticals. A hesperetin-7-O-glucoside inclusion complex with β-cyclodextrin (HEPT7G/βCD; SunActive® HCD) was formulated via the controlled enzymatic hydrolysis of hesperidin with naringinase enzyme. The conversion rate was nearly 98%, estimated using high-performance liquid chromatography analysis. The objective of this study was to investigate the stability, solubility, and spectroscopic features of the HEPT7G/βCD inclusion complex using Fourier-transform infrared (FTIR), Raman, ultraviolet–visible absorption (UV–vis), 1H- and 13C- nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), liquid chromatography/mass spectroscopy (LC–MS), scanning electron microscopy (SEM), and powdered X-ray diffraction (PXRD) spectroscopic techniques including zeta potential, Job’s plot, and phase solubility measurements. The effects of complexation on the profiles of supramolecular interactions in analytic features, especially the chemical shifts of β-CD protons in the presence of the HEPT7G moiety, were evaluated. The stoichiometric ratio, stability, and solubility constants (binding affinity) describe the extent of complexation of a soluble complex in 1:1 stoichiometry that exhibits a greater affinity and fits better into the β-CD inner cavity. The NMR spectroscopy results identified two different configurations of the HEPT7G moiety and revealed that the HEPT7G/βCD inclusion complex has both –2S and –2R stereoisomers of hesperetin-7-O-glucoside possibly in the –2S/–2R epimeric ratio of 1/1.43 (i.e., –2S: 41.1% and –2R: 58.9%). The study indicated that encapsulation of the HEPT7G moiety in β-CD is complete inclusion, wherein both ends of HEPT7G are included in the β-CD inner hydrophobic cavity. The results showed that the water solubility and thermal stability of HEPT7G were apparently increased in the inclusion complex with β-CD. This could potentially lead to increased bioavailability of HEPT7G and enhanced health benefits of this flavonoid.

The Fe–Cr–Zn system in relation with the galvanizing process in chromium-added zinc bath

Abstract Taking into account new experimental measurements, the Fe –Zn – Cr ternary system is critically modified at 460 °C. A continuous solid solution between ζ-FeZn13 and CrZn13 compounds is shown but is shared at 460 °C by the stable CrZn17 compound containing about 2 wt.% Fe. This ternary system is assessed with the CALPHAD method using the PARROT modulus of the Thermo-Calc software. The liquid and solid solution phases are modeled with Redlich– Kister –Muggianu equations. The intermetallic compounds ζ-(Fe,Cr)Zn13 and CrZn17 are treated as stoichiometric compounds in the binary systems. The experimental Fe and Cr solubilities at various temperatures modify the shape of the liquidus curve and are satisfying for industrial applications. A set of parameters consistent with most of the available experimental data on both phase diagram and solubility measurements is obtained by optimization. A comparison with previous experimental work is also presented and a reactional model between iron substrate and Zn–Cr bath is proposed. This optimization allows to interpret the growth of intermetallic layers and the formation of dross when galvanizing in Cr-added Zn bath.

Development of fast-dissolving dosage forms of curcuminoids by electrospinning for potential tumor therapy application

Curcuminoids (CUs) of antitumor and various other potential biological activities have extremely low water solubility therefore special formulation was elaborated. New fast dissolving reconstitution dosage forms of four CUs were prepared as fibrous form of 2-hydroxypropyl-β-cyclodextin (HP-β-CD). In the electrospinning process HP-β-CD could act both as solubilizer and fiber-forming agent. The solubilization efficiency of the CU-HP-β-CD systems was determined with phase-solubility measurements. The electrospun CUs were amorphous and uniformly distributed in the fibers according to XRD analysis and Raman mappings. The fibrous final products had fast (<5 min) and complete dissolution. In typical iv. infusion reconstitution volume (20 mL) fibers containing 40–80 mg of CU could be dissolved, which is similar to the currently proposed dose (<120 mg/m2). The in vitro cytostatic effect data showed that the antitumor activity of the CU-HP-β-CD complexes was similar or better compared to the free APIs.

Drug Solubilization by Means of Partition/Association Equilibrium Using a Modified Nanosized Dendrimeric Biopolymer.

The objective of this study is to elucidatethe combined effects of a novel type of material being investigated as a new excipient, an octenylsuccinate-modified dendrimer-like biopolymer (OS-DLB) and poloxamer (PLX), on the solubility of poorly water-soluble compounds. Phenytoin (PHT), griseofulvin (GSF), ibuprofen (IBU), and loratadine (LOR) were used as model compounds. Phase solubility measurements were conducted to determine the relative proportions of API, OS-DLB, and PLX that result in the most stable dendrimeric complexes. The solubilizing power of OS-DLB increases with increasing hydrophobicity of the solute. In the presence of PLX, the solubilization effect of OS-DLB is modestly accentuated for the most hydrophobic drugs (IBU and LOR) but has no effect on the least hydrophobic one (PHT). The maximum potentiation effect of PLX on the solubilizing properties of OS-DLB was observed for GSF, the drug of intermediate hydrophobicity. Three different types of solubilization profiles were obtained in the study. All three different profiles can be appropriately described by a singlesolubilization model, depending on the specific parameter values. The defining parameters of the model reflect the hydrophobicity of the drug on the one hand and, on the other hand, the inherent tendency of the drug (crystal lattice energy) toward crystallization.

Effect of Cyclodextrin Types and Co-Solvent on Solubility of a Poorly Water Soluble Drug.

The aim of the study was to investigate the solubility of piroxicam (Prx) depending on the inclusion complexation with various cyclodextrins (CDs) and on ethanol as a co-solvent. The phase-solubility method was applied to determine drug solubility in binary and ternary systems. The results showed that in systems consisting of the drug dissolved in ethanol–water mixtures, the drug solubility increased exponentially with a rising concentration of ethanol. The phase solubility measurements of the drug in aqueous solutions of CDs, β-CD and γ-CD exhibited diagrams of AL-type, whereas 2,6-dimethyl-β-CD revealed AP-type. The destabilizing effect of ethanol as a co-solvent was observed for all complexes regardless of the CD type, as a consequence of it the lowering of the complex formation constants. In systems with a higher concentration of ethanol, the drug solubility was increased in opposition to the decreasing complex formation constants. According to this study, the type of CDs played a more important role on the solubility of Prx, and the use of ethanol as a co-solvent exhibited no synergistic effect on the improvement of Prx solubility. The Prx solubility was increased again due to the better solubility in ethanol.

Physicochemical characterizations of safranal-β-cyclodextrin inclusion complexes prepared by supercritical carbon dioxide and conventional methods

In this work, inclusion complexes of safranal with β-cyclodextrin (β-CD) were prepared using supercritical carbon dioxide (SC-CO2) as well as kneading (KN), co-evaporation, and sealed heating conventional methods. Prepared complexes were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction, scanning electron microscopy and proton nuclear magnetic resonance (1H-NMR) spectroscopy. Effect of preparation method on the yield of inclusion complexes was also investigated. The SC-CO2 method was found to be the most effective preparation technique with the advantage of not using organic solvents. Effects of temperature and pressure on the properties of complexes prepared by SC-CO2 were also investigated. FT-IR and 1H-NMR results confirmed the formation of safranal-β-CD inclusion complexes prepared using all the above mentioned preparation techniques. Phase solubility and dissolution measurements revealed a ‘‘Bs’’ type solubility with an apparent stability constant (Ks) of 39.69 M−1. Initial aqueous solubility of safranal was enhanced by about 35 % upon complex formation with β-CD. Studies on dissolution rate showed a faster dissolution rate of inclusion complexes compared to pure safranal.

Electroblowing and electrospinning of fibrous diclofenac sodium-cyclodextrin complex-based reconstitution injection

Electrospinning, electroblowing and freeze-drying were investigated to prepare fast dissolving cyclodextrin-based drug-loaded solid complexes. Combining the huge surface area of fibrous mats with the capabilities of cyclodextrins to prepare a reconstitution injection was tested to overcome the instability of liquid-based products. Diclofenac sodium was used as drug with limited water solubility and 2-hydroxypropyl-β-cyclodextrin (HPβCD) as carrier and solubilizer. The applied composition of the complex was determined based on phase solubility measurements. In order to resolve the frequent unavoidable interruption of the fiber formation during electrospinning from the HPβCD solution, high-speed blowing air was coupled with the electrostatic force (electroblowing) to draw polymer-free HPβCD fibers steadily, moreover, at increased flow rates. According to the scanning electron microscopic images, X-ray diffraction, differential scanning calorimetry no traces of crystallinity of the drug were detectable in the fibers as opposed to the freeze-dried product. Reconstitution tests of the fibers showed fast dissolution obtaining clear solutions equivalent to a marketed liquid-based bolus injection. The results demonstrate the first time the viability of electroblowing for preparing drug delivery systems.

Internal consistency in aqueous geochemical data revisited: Applications to the aluminum system

Internal consistency of thermodynamic data has long been considered vital for confident calculations of aqueous geochemical processes. However, an internally consistent mineral thermodynamic data set is not necessarily consistent with calculations of aqueous species thermodynamic properties due, potentially, to improper or inconsistent constraints used in the derivation process. In this study, we attempt to accommodate the need for a mineral thermodynamic data set that is internally consistent with respect to aqueous species thermodynamic properties by adapting the least squares optimization methods of Powell and Holland (1985). This adapted method allows for both the derivation of mineral thermodynamic properties from fluid chemistry measurements of solutions in equilibrium with mineral assemblages, as well as estimates of the uncertainty on the derived results. Using a large number of phase equilibria, solubility, and calorimetric measurements, we have developed a thermodynamic data set of 12 key aluminum-bearing mineral phases. These data are derived to be consistent with Na+ and K+ speciation data presented by Shock and Helgeson (1988), H4SiO4(aq) data presented by Stefánsson (2001), and the Al speciation data set presented by Tagirov and Schott (2001). Many of the constraining phase equilibrium measurements are exactly the same as those used to develop other thermodynamic data, yet our derived values tend to be quite different than some of the others’ due to our choices of reference data. The differing values of mineral thermodynamic properties have implications for calculations of Al mineral solubilities; specifically, kaolinite solubilities calculated with the developed data set are as much as 6.75 times lower and 73% greater than those calculated with Helgeson et al. (1978) and Holland and Powell (2011) data, respectively. Where possible, calculations and experimental data are compared at low T, and the disagreement between the two sources reiterates the common assertion that low-T measurements of phase equilibria and mineral solubilities in the aluminum system rarely represent equilibrium between water and well-crystallized, aluminum-bearing minerals. As an ancillary benefit of the derived data, we show that it may be combined with high precision measurements of aqueous complex association constants to derive neutral species activity coefficients in supercritical fluids. Although this contribution is specific to the aluminum system, the methods and concepts developed here can help to improve the calculation of water–rock interactions in a broad range of earth systems.

Study and Characterization of the Antioxidant Activity of the Inclusion Complex of Apigenin with beta-Cyclodextrin and HP-beta-Cyclodextrin in solution

The formation of the complexes of Apigenin with β-Cyclodextrin (β-CD) and HP-β-Cyclodextrin (HP-β-CD) were studied by fluorescence spectra in solution. The formation constants (Ks) of complexes were determined by fluorescence method and Phase-solubility measurements. The results showed that the inclusion ability of β-Cyclodextrin and its derivative were the order: HP-β-CD> β-CD. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of Apigenin with Cyclodextrins. Kinetic studies of Scavenging of DPPH free radical with Apigenin and Cyclodextrins complexes were done. The results obtained indicated that the Apigenin/HP-β-CD complex was the most reactive form, then was β-CD complex, and last was free Apigenin.

Host–guest interaction between new nitrooxoisoaporphine and β-cyclodextrins: Synthesis, electrochemical, electron spin resonance and molecular modeling studies

A new nitrooxoisoaporphine derivative was synthetized and characterized by cyclic voltammetry and electron spin resonance. Its aqueous solubility was improved by complexes formation with β-cyclodextrin, heptakis(2,6-di-O-methyl)-β-cyclodextrin and (2-hydroxypropyl)-β-cyclodextrin. In order to assess the inclusion degree reached by nitrooxoisoaporphine in cyclodextris cavity, the stability constants of formation of the complexes were determined by phase-solubility measurements obtaining in all cases a type-AL diagram. Moreover, electrochemical studies were carried out, where the observed change in the EPC value indicated a lower feasibility of the nitro group reduction. Additionally, a detailed spatial configuration is proposed for inclusion of derivate within the cyclodextrins cavity by 2D NMR techniques. Finally, these results are further interpreted by means of molecular modeling studies. Thus, theoretical results are in complete agreement with the experimental data.

Empirical, thermodynamic and quantum-chemical investigations of inclusion complexation between flavanones and (2-hydroxypropyl)-cyclodextrins

The inclusion complexation of (2-hydroxypropyl)-cyclodextrins with flavanones was investigated by phase solubility measurements, as well as thermodynamic and quantum chemical methods. Inclusion complexes were formed between (2-hydroxypropyl)-α-cyclodextrin (HP-α-CD), (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD), (2-hydroxypropyl)-γ-cyclodextrin (HP-γ-CD) and β-cyclodextrin (β-CD) and four flavanones (naringenin, naringin, hesperetin and dihydromyricetin) in aqueous solutions and their phase solubility was determined. For all the flavanones, the stability constants of their complexes formed with different CDs followed the rank order: HP-β-CD (MW 1540)>HP-β-CD (MW 1460)>HP-β-CD (MW 1380)>β-CD>HP-γ-CD>HP-α-CD. Experimental results and quantum chemical calculations showed that the ability of flavanones to form inclusion complex with (2-hydroxypropyl)-cyclodextrins was determined by both the steric effect and hydrophobicity of the flavanones. For flavanones that have similar molecular volumes, the hydrophobicity of the molecule was the main determining factor of its ability to form inclusion complexes with HP-β-CD, and the hydrophobicity parameter Log P is highly correlated with the stability constant of the complexes. Results of thermodynamic study demonstrated that hydrophobic interaction is the main driving force for the formation process of the flavanone-CD inclusion complexes. Quantum chemical analysis of the most active hydroxyl groups and HOMO (the highest occupied molecular orbital) showed that the B ring of the flavanones was most likely involved in hydrogen bonding with the side groups in the cavity of the CDs, through which the inclusion complex was stabilised.

Simultaneously Improving the Mechanical Properties, Dissolution Performance, and Hygroscopicity of Ibuprofen and Flurbiprofen by Cocrystallization with Nicotinamide

To be fully exploitable in both formulation and manufacturing, a drug cocrystal needs to demonstrate simultaneous improvement of multiple key pharmaceutical properties over the pure drug crystal. The present work was aimed at investigating such feasibility with two model profen-nicotinamide cocrystals. Phase pure 1:1 ibuprofen-nicotinamide and flurbiprofen-nicotinamide cocrystals were prepared from solutions through rapid solvent removal using rotary evaporation,and characterized by DSC, PXRD, FTIR, phase solubility measurements, equilibrium moisture sorption analysis, dissolution testing and tabletability analysis. Temperature-composition phase diagrams constructed from DSC data for each profen and nicotinamide crystal revealed the characteristic melting point of the 1:1 cocrystal as well as the eutectic temperatures and compositions. Both cocrystals exhibited higher intrinsic dissolution rates than the corresponding profens. The cocrystals also sorbed less moisture and displayed considerably better tabletability than the individual profens and nicotinamide. Phase behaviors of 1:1 profen-nicotinamide cocrystal systems were delineated by constructing their temperature-composition phase diagrams. Cocrystallization with nicotinamide can simultaneously improve tableting behavior, hygroscopicity, and dissolution performance of ibuprofen and flurbiprofen. This could pave the way for further development of such cocrystal systems into consistent, stable, efficacious and readily manufacturable drug products.

Evaluation of a cationic calix[4]arene: Solubilization and self-aggregation ability

Water-soluble calixarenes are promising macrocyclic compounds which have found numerous applications in chemistry and biology. However, these compounds have been less studied in regard to their behavior in aqueous solutions and mechanisms of drug solubilization. The present work is devoted to the evaluation of the solubilizing properties and estimation of self-aggregation ability of positively charged 5,11,17,23-tetrakis(trimethylammoniomethyl)-25,26,27,28-tetrapropoxy-calix[4]arene tetrachloride (aminocalix), including comparisons with a series of pharmaceutically relevant cyclodextrins. Phase-solubility measurements of the drugs with aminocalix and various cyclodextrins were carried out. Aminocalix showed a solubilizing ability comparable to the cyclodextrins. The drug solubility enhancement caused by the aminocalix was studied and was found to be maximal for steroid drugs. An attempt to understand the solubilizing mechanism of aminocalix was undertaken based on correlation analysis between physical and physico-chemical properties of the drugs from one side and the solubilizing ability of aminocalix from the other. Correlation analysis supports the supposition that the solubilizing effect of aminocalix is based on interaction of the drug with aminocalix aggregates rather than on inclusion complexation. UV-absorbance, osmolality and surface tension concentration dependences of aminocalix showed an inflection at 1% (w/v) which was initially related to the transition from monomers to micelles. However, dynamic light scattering and transmission electron microscopy measurements revealed that likely vesicles of diverse size exist at 0.1% (w/v) concentration. Thus the 1% (w/v) inflection point was interpreted to be spontaneous reordering of the vesicles between two different size populations.

Hydrogenation of phenol with supported Rh catalysts in the presence of compressed CO 2: Its effects on reaction rate, product selectivity and catalyst life

Hydrogenation of phenol to cyclohexanone and cyclohexanol in/under compressed CO 2 was examined using commercial Rh/C and Rh/Al 2O 3 catalysts to investigate the effects of CO 2 pressurization on the total conversion and the product selectivity. Although the total rate of phenol hydrogenation with Rh/C was lowered by the presence of CO 2, the selectivity to cyclohexanone was improved at high conversion levels >70%. On the other hand, the activity of Rh/Al 2O 3 was completely lost in an early stage of reaction. The features of these multiphase catalytic hydrogenation reactions using compressed CO 2 were studied in detail by phase behavior and solubility measurements, in situ high-pressure FTIR for molecular interactions of CO 2 with reacting species and formation/adsorption of CO on the catalysts, and simulation of reaction kinetics using a simple model. The CO 2 pressurization was shown to suppress the hydrogenation of cyclohexanone to cyclohexanol, improving the selectivity to cyclohexanone. The formation and adsorption of CO were observed for the two catalysts at high CO 2 pressures in the presence of H 2, which was one of important factors retarding the rate of hydrogenation in the presence of CO 2. It was further indicated that the adsorption of CO on Rh/Al 2O 3 was strong and caused the complete loss of its activity.

IMPROVEMENT OF GALANGIN SOLUBILITY USING NATIVE AND DERIVATIVE CYCLODEXTRINS: AN UV-Vis AND NMR STUDY

The slightly water-soluble flavonoid galangin (G) and its inclusion with either β-cyclodextrin (βCD), hydro xypropyl-β-cyclodextrin (HPβCD) or Heptakis-2,6-O-di methyl-β-cyclodextrin (DMβCD) were investigated. The stoichiometric ratios and stability constants describing the extent of the formation of the complexes have been determined by phase-solubility measurements; in all cases type-AL diagrams have been obtained (soluble 1:1 complexes). The results showed that the complex efficiency of βCD and its derivatives was the order: DMβCD > HPβCD > βCD. The NMR study indicate that the inclusion of galangin in the cyclodextrin nano-cavity is different depending on the type of cyclodextrin used.

Molecular encapsulation of 5-nitroindazole derivatives in 2,6-dimethyl-β-cyclodextrin: Electrochemical and spectroscopic studies

Four different 5-nitroindazole derivatives ( 1– 4) and its inclusion with Heptakis(2,6-di- O-methyl)-β-cyclodextrin (DMβCD) were investigated. The stoichiometric ratios and stability constants describing the extent of formation of the complexes were determined by phase-solubility measurements obtaining in all cases a type-A L diagram. Also electrochemical studies were carried out, where the observed change in the E PC value indicated a lower feasibility of the nitro group reduction. The same behavior was observed in the ESR studies. The detailed spatial configuration is proposed based on 2D NMR methods. These results are further interpreted using molecular modeling studies. The latter results are in good agreement with the experimental data.

Preparation and characterization of the inclusion complex of Baicalin (BG) with β-CD and HP-β-CD in solution: An antioxidant ability study

The formation of the complexes of BG with β-CD and HP-β-CD was studied by UV–vis absorption spectroscopy, fluorescence spectra, Phase-solubility measurements and nuclear magnetic resonance spectroscopy (NMR) in solution. The formation constants ( K) of complexes were determined by fluorescence method and Phase-solubility measurements. The results showed that the inclusion ability of β-CD and its derivatives was the order: HP-β-CD > β-CD. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of BG with CDs. The antioxidant ability studies of BG and CDs complexes were done. The results obtained indicated that the BG/HP-β-CD complex was the most reactive form, and then was the BG/β-CD complex; the last was BG. Special configuration of complex has been proposed on NMR technique.