FT-IR and FT-Raman vibrational spectra and molecular structure investigation of nicotinamide: A combined experimental and theoretical study

Analysis of the Dissolution Behavior of Theophylline and Its Cocrystal Using ATR-FTIR Spectroscopic Imaging

Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic imaging is a powerful tool to visualize the distribution of components, and it has been used to analyze drug release from tablets. In this work, ATR-FTIR spectroscopic imaging was applied for observing the dissolution of molecular crystals from tablet compacts. The IR spectra provided chemically specific information about the transformation of crystal structures during the dissolution experiments. Theophylline (TPL) anhydrate and its cocrystals were used as model systems of molecular crystals. The IR spectra during the dissolution of TPL revealed information about the crystal structure of TPL, which transformed from anhydrate to monohydrate in water. During a dissolution test of a model cocrystal system, it was suggested that an active pharmaceutical ingredient (API) and a coformer were dissolved in water simultaneously. The IR spectra that were acquired during the dissolution of a cocrystal tablet showed new spectral bands attributed to the API after 5 min. This suggested that the precipitation of API was observed during the dissolution experiment. Measurements from ATR-FTIR spectroscopic imaging can visualize the drug release from the tablet and determine the transformation of molecular crystals during their dissolution. These results will have an impact on clarifying the dissolution mechanism of molecular crystals.

First cocrystal of esculetin: simultaneously optimized in vitro/vivo properties and antioxidant effect

Esculetin (ELT) is one of the best-known and simplest coumarins with powerful natural antioxidant effects but insoluble and difficult to absorb. In order to overcome the problems, cocrystal engineering was first applied to ELT in this paper. Nicotinamide (NAM) was selected as the coformer for its excellent water solubility and potential synergistic antioxidant effect with ELT. The structure of the ELT-NAM cocrystal was successfully prepared and characterized by IR, SCXRD, PXRD, and DSC-TG. Furthermore, the in vitro/vivo properties and antioxidant effects of the cocrystal were adequately studied. The results highlight that the ELT obtained tremendous improvements in water solubility and bioavailability after cocrystal formation. Meanwhile, the synergistic enhancement of ELT with NAM in antioxidant effect was demonstrated by the DPPH assay. Ultimately, the simultaneously optimized in vitro/vivo properties and antioxidant activity of the cocrystal created an improved practical effect of hepatoprotective in rat experiments. The investigation is significant for developing coumarin drugs represented by ELT.

Preparation of niacinamide imprinted starch-based biomaterials for treating of hyperpigmentation

The aim of this study was to prepare niacinamide (NA) imprinted biomaterials for treating hyperpigmentation using mungbean starch (MS), PVA, and plasticizers (glycerol (GL) and citric acid (CA)). Biomaterials and NA were characterized by FE-SEM, FT-IR, and ¹H NMR. To evaluate the applicability of the NA imprinted biomaterials for a transdermal drug delivery system (TDDS), NA release experiment was conducted in different pH and temperature conditions. Results of NA release properties indicated that NA was released about 99 % rapidly in the initial 10 min. NA release in low pH and high temperature was also higher than that in high pH and low temperature. The determination of experimental conditions and the analysis of NA release results were achieved using response surface methodology (RSM). Results of NA release using artificial skin indicated that NA release from NA imprinted biomaterials was increased at a relatively steady rate for 90 min. To verify for treating hyperpigmentation of the prepared biomaterials, tyrosinase inhibitory and antioxidant inhibitory were performed. Results indicated that NA imprinted biomaterials with the addition of CA exhibited 55.8 % of tyrosinase inhibitory and 73.0 % of antioxidant inhibitory. In addition, their ability to inhibit melanin synthesis in B16F10 cells was evaluated.

A molecularly enhanced proof of concept for targeting cocrystals at molecular scale in continuous pharmaceuticals cocrystallization

It is impossible to optimize a process for a target drug product with the desired profile without a proper understanding of the interplay among the material attributes, the process parameters, and the attributes of the drug product. There is a particular need to bridge the micro- and mesoscale events that occur during this process. Here, we propose а molecular engineering methodology for the continuous cocrystallization process, based on Raman spectra measured experimentally with a probe and from quantum mechanical calculations. Using molecular dynamics simulations, the theoretical Raman spectra were calculated from first principles for local mixture structures under an external shear force at various temperatures. A proof of concept is developed to build the process design space from the computed data. We show that the determined process design space provides valuable insight for optimizing the cocrystallization process at the nanoscale, where experimental measurements are difficult and/or inapplicable. The results suggest that our method may be used to target cocrystallization processes at the molecular scale for improved pharmaceutical synthesis.

Chitin Nanofibril-Nanolignin Complexes as Carriers of Functional Molecules for Skin Contact Applications

Chitin nanofibrils (CN) and nanolignin (NL) were used to embed active molecules, such as vitamin E, sodium ascorbyl phosphate, lutein, nicotinamide and glycyrrhetinic acid (derived from licorice), in the design of antimicrobial, anti-inflammatory and antioxidant nanostructured chitin nanofibrils–nanolignin (CN-NL) complexes for skin contact products, thus forming CN-NL/M complexes, where M indicates the embedded functional molecule. Nano-silver was also embedded in CN-NL complexes or on chitin nanofibrils to exploit its well-known antimicrobial activity. A powdery product suitable for application was finally obtained by spray-drying the complexes co-formulated with poly(ethylene glycol). The structure and morphology of the complexes was studied using infrared spectroscopy and field emission scanning electron microscopy, while their thermal stability was investigated via thermo-gravimetry. The latter provided criteria for evaluating the suitability of the obtained complexes for subsequent demanding industrial processing, such as, for instance, incorporation into bio-based thermoplastic polymers through conventional melt extrusion. In vitro tests were carried out at different concentrations to assess skin compatibility. The obtained results provided a physical–chemical, morphological and cytocompatibility knowledge platform for the correct selection and further development of such nanomaterials, allowing them to be applied in different products. In particular, chitin nanofibrils and the CN-NL complex containing glycyrrhetinic acid can combine excellent thermal stability and skin compatibility to provide a nanostructured system potentially suitable for industrial applications.

Electrode surface embedded manganese(iii)–pincer complexes: efficient electrocatalysts for the oxygen evolution reaction

Highly stable and robust gold electrode surface anchored Mn(iii)–pincer complex exhibits an excellent electrocatalytic activity towards the oxygen evolution reaction at a low overpotential with a medium Tafel slope under neutral pH condition.

Kinetics of the Release of Nicotinamide Absorbed on Partially Neutralized Poly(acrylic-co-methacrylic acid) Xerogel under the Conditions of Simultaneous Microwave Heating and Cooling

The kinetics of release of nicotinamide (NIAM) that was absorbed on partially neutralized poly(acrylic-co-methacrylic) (PAM) xerogel/hydrogel, under the conditions of simultaneous microwave heating and cooling (SMHC) were examined. The kinetics curves of NIAM release into an aqueous solution at temperatures of 308-323 K were recorded. By applying the model-fitting method (MFM), it was found that the kinetics of NIAM release can be modeled by a kinetic model of a first-order chemical reaction. The values of the release rate constants (k_M) at different temperatures were calculated, and their values were found to be within the range 8.4 10^-3 s ^-1-15.7 10^-3 s^-1. It has been established that the Arrhenius equation was valid even in the conditions of SMHC. The values of the kinetic parameters (activation energy (Ea) and pre-exponential factor (A) of the NIAM release process adsorbed on PAM xerogel/hydrogel were calculated as follows: Ea = 25.6 kJ/mol and ln (A/s^-1) = 5.21. It has been proven that the higher value of the rate constant at SMHC in relation to CH is not a consequence of the overheating of the reaction system or the appearance of "hot-points". The values of change of the enthalpy of activation (ΔH*) and the change of entropy of activation (ΔS*) were calculated as follows: ΔH* = +23.82 kJ/mol and ΔS* = -201.4 J/mol K. The calculated higher values of the kinetic parameters and thermodynamic parameters of activation are explained by the formation of a specific activated complex under SMHC, whose structure and degree of order are different than in the one formed under CH.

Combined Cutaneous Therapy Using Biocompatible Metal-Organic Frameworks

Combined therapies emerge as an interesting tool to overcome limitations of traditional pharmacological treatments (efficiency, side effects). Among other materials, metal-organic frameworks (MOFs) offer versatilities for the accommodation of multiple and complementary active pharmaceutical ingredients (APIs): accessible large porosity, availability of functionalization sites, and biocompatibility. Here, we propose topical patches based on water-stable and biosafe Fe carboxylate MOFs (MIL-100 and MIL-127), the biopolymer polyvinyl alcohol (PVA) and two co-encapsulated drugs used in skin disorders (azelaic acid (AzA) as antibiotic, and nicotinamide (Nic) as anti-inflammatory), in order to develop an advanced cutaneous combined therapy. Exceptional MOF drug contents were reached (total amount 77.4 and 48.1 wt.% for MIL-100 and MIL-127, respectively), while an almost complete release of both drugs was achieved after 24 h, adapted to cutaneous delivery. The prepared cutaneous PVA-MOF formulations are safe and maintain the high drug-loading capacity (total drug content of 38.8 and 24.2 wt.% for MIL-100 and MIL-127, respectively), while allowing a controlled delivery of their cargoes, permeating through the skin to the active target sites. The total amount of drug retained or diffused through the skin is within the range (Nic), or even better (AzA) than commercial formulations. The presented results make these drug combined formulations promising candidates for new cutaneous devices for skin treatment.

Non-linear optical properties of polystyrene and polyvinyl alcohol composites with 4-methoxy-1-naphthol

The analysis of the NLO properties of 4-methoxy-1-naphthol (4M1N) reveals that this molecule has the value of polarizability tensor, α, more than 340% greater than that obtained, at the same level of theory, for urea molecule. This improvement grows to 500% when the second-order hyperpolarizability is considered. Calculations performed within LR-PCM-B3LYP/6-311+G(3d,2p) model proved that embedding of 4M1N in the polymer matrix significantly improved these results suggesting applications of 4M1N as the cheap and effective NLO material. The molecule was also studied, both theoretically and experimentally, to determine its full vibrational characterisation and structural description. Calculations were performed with HF, MP2, SVWN and B3LYP methods, in two, varying in size, basis sets, to find optimized structures, conformational isomers and UV–VIS, IR and Raman spectra. The accordance of simulated oscillation and absorption spectra with experimental ones is very good; IR values are slightly red-shifted. NBO charge distribution analysis was made to generate frontier orbitals and find most reactive parts of the molecule.

Benzodiazepines co-crystals screening using FTIR and Raman spectroscopy supported by differential scanning calorimetry

Co-crystals, which are defined as "solids that are crystalline materials composed of two or more molecules in the same crystal lattice" have recently been the focus of increased interest in the pharmaceutical industry since co-crystallization can improve unfavorable physicochemical properties of active pharmaceutical ingredients. Thus, the quest for new co-crystal screening methods has become an issue of importance. The aim of this work was, therefore, to show to what extent expanded methodology based on FTIR and Raman spectroscopy supported by the DSC method can be used as a reliable tool to screen co-crystallization. Because co-crystals of benzodiazepines had not yet been obtained, a set of 72 binary mixtures composed of eight 1,4-benzodiazepine derivatives and nine coformers were used as model substances. Potential co-crystals were prepared in solid-state by liquid-assisted grinding procedure. The characteristic FTIR and Raman bands which reflect hydrogen bond formation between benzodiazepine and coformer were used as proof of co-crystal creation. DSC was used as a supporting tool to reflect the phase transitions which occur during co-crystallization. As a result of the study, four potential co-crystals can be selected: lorazepam with nicotinamide, chlordiazepoxide with p-aminobenzoic and saccharin, and estazolam with fumaric acid. The detailed spectral and thermal characteristics of these systems are presented in this work. Thus, the proposed methodology of co-crystal screening based on FTIR and Raman data supported by the DSC examination of phase transitions facilitates the screening and detection of benzodiazepine co-crystal prepared by short time components ground with a slight additional volume of solvent.

A New Ferulic Acid-Nicotinamide Cocrystal With Improved Solubility and Dissolution Performance

Among the various strategies for increasing aqueous solubility of pharmaceutical substances, cocrystals have been emerging as a promising alternative. The ferulic acid (FEA) is a molecule with limited aqueous solubility, but with an interesting pharmacological activity, highlighting its antitumor potential. This study presents the characterization and physicochemical properties of a new cocrystal based on FEA and nicotinamide (NIC). The FEA-NIC cocrystal was obtained by solvent evaporation technique and physicochemically characterized by differential scanning calorimetry, powder X-ray diffraction, Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance and scanning electron microscopy. The content determination and dissolution profile in different media were analyzed by high-performance liquid chromatography. The results obtained with the characterization techniques indicated the obtainment of an anhydrous cocrystal of FEA and NIC at a 1:1 molar ratio. The method was reproducible and obtained a high yield, of approximately 99%. In addition, a 70% increase in the FEA solubility in the cocrystal and a better dissolution performance than the physical mixture in pH 6.8 were achieved.

Formation of Prenylated Chalcone Xanthohumol Cocrystals: Single Crystal X-Ray Diffraction, Vibrational Spectroscopic Study Coupled with Multivariate Analysis

Four novel xanthohumol (XN) cocrystals with pharmaceutically acceptable coformers, such as nicotinamide (NIC), glutarimide (GA), acetamide (AC), and caffeine (CF) in the 1:1 stoichiometry were obtained by the slow evaporation solution growth technique. The structure of the cocrystals was determined by single crystal X-ray diffraction. The analysis of packing and interactions in the crystal lattice revealed that molecules in the target cocrystals were packed into almost flat layers, formed by the O–H⋅⋅⋅O, O–H⋅⋅⋅N, and N–H⋅⋅⋅O-type contacts between the xanthohumol and coformer molecules. The results provided details about synthons responsible for crystal net stabilization and all hydrogen bonds observed in the crystal lattice. The main synthon was formed via the hydrogen bond between the hydroxyl group in the B ring of XN and coformers. The three-dimensional crystal lattice was stabilized by the hydrogen XN−XN interactions whereas the π–π stacking interactions played an additional role in layer binding, with the exception of low quality cocrystals formed with caffeine. Application of FTIR and Raman spectroscopy confirmed that the crystalline phase of obtained cocrystals was not a simple combination of individual components and completely different crystal phases resulted from the effect of intermolecular interactions. The multivariate analysis showed the changes in the spectra, and this technique can be applied in a combination with vibrational spectroscopy for fast screening of new crystal phases. Additionally, the solubility studies of pure XN and its cocrystals exhibited a 2.6-fold enhancement in XN solubility in aqueous solution for XN–AC and, to a lesser extent, for other cocrystals.

Biological Nicotinamide Cofactor as a Redox-Active Motif for Reversible Electrochemical Energy Storage

Nicotinamide adenine dinucleotide (NAD⁺ ) is one of the most well-known redox cofactors carrying electrons. Now, it is reported that the intrinsically charged NAD⁺ motif can serve as an active electrode in electrochemical lithium cells. By anchoring the NAD⁺ motif by the anion incorporation, redox activity of the NAD⁺ is successfully implemented in conventional batteries, exhibiting the average voltage of 2.3 V. The operating voltage and capacity are tunable by altering the anchoring anion species without modifying the redox center itself. This work not only demonstrates the redox capability of NAD⁺ , but also suggests that anchoring the charged molecules with anion incorporation is a viable new approach to exploit various charged biological cofactors in rechargeable battery systems.

Polarized Two-Photon Absorption and Heterogeneous Fluorescence Dynamics in NAD(P)H

Two-photon absorption (2PA) finds widespread application in biological systems, which frequently exhibit heterogeneous fluorescence decay dynamics corresponding to multiple species or environments. By combining polarized 2PA with time-resolved fluorescence intensity and anisotropy decay measurements, we show how the two-photon transition tensors for the components of a heterogeneous population can be separately determined, allowing structural differences between the two fluorescent states of the redox cofactor NAD(P)H to be identified. The results support the view that the two states correspond to alternate configurations of the nicotinamide ring, rather than folded and extended conformations of the entire molecule.

Toxic target of trans-crotonaldehyde in mitochondria altered by diallyl disulfides for anti-myocardial ischemia

The purposes of this study were to probe spectral behaviors of the toxic targets in trans-crotonaldehyde (TCA) in mitochondria altered by diallyl disulfides (DADS) derived from garlic. Ultraviolet absorption spectra showed that when ethanol as a solvent, the DADS blue shifted the peak of TCA from 318 nm to 312 nm. In mitochondria, the DADS further blue displaced the peak of TCA from 312 nm to 308 nm. Raman spectra displayed that the SS of DADS directly interacted with the CC toxic target of TCA, then the CCC of DADS interacted with the CHO toxic target of TCA. When DADS to TCA was 1:2, the DADS was the most powerful for the removal of the CC and CHO toxic targets of TCA. Study suggested that the SS of DADS altered the CC toxic target of TCA, while the CCC of DADS eliminated the CHO toxic target of TCA via local electron delocalization. The above two together clearly depicted the spectral behaviors of the toxic targets of TCA in mitochondria altered by DADS. These results are of great significance and value to elucidate the effects of garlic organic polysulfide on myocardial ischemia for the extensive development and use of garlic extracts.

Investigating the Influence of Polymers on Supersaturated Flufenamic Acid Cocrystal Solutions

The development of enabling formulations is a key stage when demonstrating the effectiveness of pharmaceutical cocrystals to maximize the oral bioavailability for poorly water soluble drugs. Inhibition of drug crystallization from a supersaturated cocrystal solution through a fundamental understanding of the nucleation and crystal growth is important. In this study, the influence of the three polymers of polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and a copolymer of N-vinly-2-pyrrodidone (60%) and vinyl acetate (40%) (PVP-VA) on the flufenamic acid (FFA) crystallization from three different supersaturated solutions of the pure FFA and two cocrystals of FFA-NIC CO and FFA-TP CO has been investigated by measuring nucleation induction times and desupersaturation rates in the presence and absence of seed crystals. It was found that the competition of intermolecular hydrogen bonding among drug/coformer, drug/polymer, and coformer/polymer was a key factor responsible for maintaining supersaturation through nucleation inhibition and crystal growth modification in a cocrystal solution. The supersaturated cocrystal solutions with predissolved PEG demonstrated more effective stabilization in comparison to the pure FFA in the presence of the same polymer. In contrast, neither of the two cocrystal solutions, in the presence of PVP or PVP-VA, exhibited a better performance than the pure FFA with the same predissolved polymer. The study suggests that the selection of a polymeric excipient in a cocrystal formulation should not be solely dependent on the interplay of the parent drug and polymer without considering the coformer effects.

Theophylline-nicotinamide cocrystal formation in physical mixture during storage

Pharmaceutically relevant properties, such as solubility and dissolution rate, of active pharmaceutical ingredients can be enhanced by cocrystal formation. Theophylline and nicotinamide are known to form cocrystals, for example if subjected to solid-state grinding. However, under appropriate conditions, cocrystals can also form in physical mixtures without any mechanical activation. The purpose of this work was to study whether theophylline and nicotinamide could form cocrystals spontaneously, without mechanical activation. Crystalline theophylline and nicotinamide powders were gently mixed manually in a 1:1 molar ratio and stored at different relative humidity and temperature conditions. The solid state of the samples was analyzed by differential scanning calorimetry, Raman spectroscopy and X-ray powder diffractometry. Three different variations of theophylline were used as starting materials, e.g., two size fractions of theophylline anhydrate (large 710 μm-1 mm and small 180-355 μm), and monohydrate (recrystallized from water). As a reference, anhydrous theophylline-nicotinamide cocrystals were prepared by solid-state grinding. The results of this study indicate that theophylline-nicotinamide cocrystals can form without any mechanical activation from physical mixtures of theophylline and nicotinamide during storage. For anhydrous samples, storage humidity was found to be a critical parameter for cocrystal formation. Increasing temperature was also found to have an accelerating effect on the transformation. The effect of particle size of anhydrous theophylline on the transformation rate could not be completely resolved; DSC and Raman indicated slightly faster transformation with a physical mixture prepared from large size fraction of anhydrous theophylline, but the differences were only minor. Cocrystal formation was also observed in the physical mixture prepared from theophylline monohydrate, but the rate was not as high as with samples prepared from anhydrous material.

Molecular geometry, conformational, vibrational spectroscopic, molecular orbital and Mulliken charge analysis of 2-acetoxybenzoic acid

The Fourier transform infrared (FT-IR) and FT-Raman spectra of 2-acetoxybenzoic acid (2ABA), a painkiller agent were recorded in the region 4000-450 cm(-1) and 5000-50 cm(-1) respectively. Hartree Fock (HF) and Density functional theory (DFT) methods have been used to determine its optimized geometrical parameter, atomic charges, and vibrational wavenumbers and intensity of the vibrational bands of the title molecule. The computed vibrational wave numbers were compared with the FT-IR and FT-Raman experimental data. The computational calculations were done at HF and DFT/B3LYP level with 6-311++G(d,p) basis set. The complete vibrational assignments were performed on the basis of the potential energy distribution (PED) analysis. The Mulliken charges, UV-Visible spectral analysis and HOMO-LUMO energy gap have been calculated and reported. The B3LYP method of calculated parameters is a good complement with the experimental findings. The thermodynamic properties like entropy, heat capacity and zero vibrational energy have been calculated and discussed. The electrostatic potential (ESP) contour surface and molecular electrostatic potential (MESP) of the molecule were constructed.

Modeling the effect of H-bonding interactions and molecular packing on the molecular structure of [Ag(ethylnicotinate)(2)]NO (3) complex

The gas phase molecular structure of a single isolated molecule of [Ag(Etnic)(2)NO(3)];1 where Etnic = Ethylnicotinate was calculated using B3LYP method. The H-bonding interaction between 1 with one (complex 2) and two (complex 3) water molecules together with the dimeric formula [Ag(Etnic)(2)NO(3)](2);4 and the tetrameric formula [Ag(Etnic)(2)NO(3)](4);5 were calculated using the same level of theory to model the effect of intermolecular interactions and molecular packing on the molecular structure of the titled complex. The H-bond dissociation energies of complexes 2 and 3 were calculated to be in the range of 12.220-14.253 and 30.106-31.055 kcal mol(-1), respectively, indicating the formation of relatively strong H-bonds between 1 and water molecules. The calculations predict bidentate nitrate ligand in the case of 1 and 2, leading to distorted tetrahedral geometry around the silver ion with longer Ag-O distances in case of 2 compared to 1, while 3 has a unidentate nitrate ligand leading to a distorted trigonal planar geometry. The packing of two [Ag(Etnic)(2)NO(3)] complex units; 4 does not affect the molecular geometry around Ag(I) ion compared to 1. In the case of 5, the two asymmetric units of the formula [Ag(Etnic)(2)NO(3)] differ in the bonding mode of the nitrate group, where the geometry around the silver ion is distorted tetrahedral in one unit and trigonal planar in the other. The calculations predicted almost no change in the charge densities at the different atomic sites except at the sites involved in the C-H⋯O interactions as well as at the coordinated nitrogen of the pyridine ring.

Vibrational and electronic investigations, thermodynamic parameters, HOMO and LUMO analysis on crotonaldehyde by ab initio and DFT methods

The energy, geometrical parameters and vibrational wavenumbers of crotonaldehyde were calculated by using ab initio and B3LYP with 6-31G(d,p) and 6-311G(d,p) basis sets. The FT-IR and FT-Raman spectra for liquid state crotonaldehyde have been recorded in the region 3400-400 cm(-1) and 3400-100 cm(-1), respectively and compared with the theoretical spectrographs constructed from the scaled harmonic vibrational frequencies calculated at HF and DFT levels. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. Detailed interpretations on vibrational modes have been made on the observed and theoretical spectra and PED for each mode was also reported more precisely. HOMO and LUMO energy levels are constructed and the corresponding theoretical frontier energy gaps are calculated to realise the charge transfer occurring in the molecule. The thermodynamic properties of the title compound have been calculated at different temperatures and the results reveals the standard heat capacities (C(0)(p)), standard entropies (S(0)) and standard enthalpy changes (ΔH(0)) increases with rise in temperature.