Caffeine Molecules Research Articles

Structural investigation of caffeine monolayers on Au(111)

The asymmetric and achiral character of caffeine (${\mathrm{C}}_{8}{\mathrm{H}}_{10}{\mathrm{N}}_{4}{\mathrm{O}}_{2}$) leads to two on-surface chiralities which has an impact on its on-surface formation. An analysis of its on-surface behavior reveals new insights of its crystallite growth. In this study the structural formation of caffeine monolayers on a Au(111) surface was analyzed by scanning tunneling microscopy (STM), low energy electron diffraction (LEED), x-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. The monolayers were prepared by molecular beam epitaxy (MBE) and analyzed at room temperature. Caffeine molecules self-assemble in a quasihexagonal phase on Au(111) similar to the high-temperature $\ensuremath{\alpha}$ phase. Two mirrored hexagonal domains are present with respect to the surface. Within the XPS measurements, no strong surface interaction was found. Therefore, a theoretical analysis of a hypothetical free-standing caffeine monolayer structure was performed by ab initio simulations. We found that a caffeine monolayer with three molecules per unit cell is preferable to one with just a single molecule, as could be expected from the LEED pattern.

Amyloid Aggregation of Insulin: An Interaction Study of Green Tea Constituents

Exogenous insulin, used as a therapeutic agent for diabetes, forms insoluble deposits containing amyloid fibrillar structures near the administration site. We have analyzed the in vitro anti-amyloid activity of four green tea constituents: (-)-epigallocatechin gallate (EGCG), (-)-epicatechin (EC), gallic acid (GA), caffeine (CF), and their equimolar mixtures. Regarding individually tested compounds, only EGCG inhibited the fibrillization process. The individual EC, GA, and CF molecules were ineffective. The presence of EGCG in equimolar combinations with GA, EC, or CF was required for the inhibitory activity of most mixtures. Molecular docking revealed that EGCG interacts with an essential amyloidogenic region of insulin chain B. Individually inactive GA had a potentiating effect on the activity of EGCG. In contrast, EC and CF had a negative impact on the activity of the mixtures. We have observed diverse morphology and the amount of insulin amyloid aggregates formed in the presence of studied compounds. The distinct types of amyloid aggregates created in vitro in the presence of EGCG and other green tea constituents were characterized. Results indicate that the biological activity of individual molecules is not directly applicable to the pooled samples effects prediction.

The effect of caffeine molecule on the physico-chemical properties of blended cement

Caffeine is a nontoxic and eco-friendly natural molecule used in the food industry as well as a corrosion inhibitor in various corrosive media. However, its behavior and performance as an additive in the construction industry has not been explored. This paper investigates the effect of caffeine as an additive on strength, water demands, setting time and hydration mechanism of cement. In the first instance, the water demand, volume expansion and setting time of cement pastes, incorporating 0, 25, 50 and 75 ppm of caffeine were determined. In the second section, the rate of hydration and cement pastes’ products were conducted by means of X–ray diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR), thermal analysis and scanning electron microscope (SEM) at 28 days. Finally, the cement mortars’ compressive strengths were determined at 2, 7 and 28 days intervals. Consequently, mortars containing 75 ppm caffeine registered higher strength than the pure cement mortars due to high quantities of primary C-S-H gel, chemically bound water, compact structure at 28 days. Furthermore, by result of analysis and experiments, it was determined that caffeine had no negative effect on cement.

Tuning the charge carrier density and exciton pair separation in electrospun 1D ZnO-C composite nanofibers and its effect on photodegradation of emerging contaminants

Maximizing anion (carbon) doping is thought to increase the charge carrier density in ZnO and other semiconductor metal oxide photocatalysts. It also enhances the photocatalytic activity of ZnO nanostructures by imparting visible light responsiveness. However, the effect of the carbon source on the doping efficiency, and in turn on the photocatalytic activity of ZnO nanostructures has been overlooked thus far. In this study one dimensional (1D) ZnO-Carbon composite nanofibers were prepared from different polymer (polyacrylonitrile, polystyrene, polyvinylpyrrolidone) precursor solutions and the C-doping efficiency and its effect on the photocatalytic activity were studied. The prepared nanofiber photocatalysts were characterized by XRD, XPS, FE-SEM, BET, TGA, FT-IR, photoelectrochemical and optical analyses techniques. Based on the thermal degradation profile of the polymer sources, the C-doping efficiencies varied among the samples prepared and so does their photocatalytic activity. Caffeine molecule was selected as a model emerging contaminant and its photodegradation was analyzed in the presence of the as-prepared photocatalysts. Upon the C-doping, new energy level was introduced within the bandgap of ZnO that lowers its bandgap energy by 0.35 eV. Additionally, the charge carrier density of ZnO increased and the flat band potential showed positive shift. These, together with the 1D nature of the photocatalysts, enhanced the photocatalytic activity of pristine ZnO by ~58% and 2.8 folds faster kinetics. Mechanistic study showed that hydroxyl radicals were the most active reactive species responsible for the caffeine molecule degradation. This study underscores that the photocatalytic activity of ZnO for the degradation of environmental pollutants can be maximized by C-doping through careful selection of the carbon source.

Caffeine and Peripheral Blood Flow

Caffeine is the drug of choice for adults of the world. It is commonly found in the favorite beverages they consume such as coffee, energy drinks, soft drinks and tea. The caffeine molecule is a decorative sculpture that helps visitors identify the recently-constructed Chemistry and Chemical Biology Building on the Busch Campus of Rutgers University, Piscataway, New Jersey.

Application of date stone activated carbon for the removal of caffeine molecules from water

Date stone activated carbon was prepared by impregnating the grounded date stone in 40% phosphoric acid solution. The obtained date stone activated carbon (DSAC) was applied against the caffeine mixed water to scavenge the caffeine molecules from the water. The independent variables such as activated carbon dosage (0.5–10 g/L), contact time (1–80 min), initial concentration of the caffeine (12–260 ppm), and temperature (25–50 °C) were varied and observed its effect on the adsorption efficiency of the DSAC. The recovery of the adsorbed caffeine molecules from the surface of DSAC was also studied with NaOH (0.1 N) solution and hot water. The 8 g/L activated carbon dosage was set for recovery after allowing them to adsorb in 100 ± 3 ppm caffeine solution. The desorption efficiency of date stone activated carbon was observed around 27.90 ± 1.08% for hot water and 28.84 ± 0.64% for NaOH (0.1 N) solution. The date stone activated carbon are an efficient adsorbent, which was applied successfully in scavenging and recovery caffeine from the aqueous solutions.

Femtosecond nonadiabatic cascade and subsequent photofragmentation of XUV excited caffeine molecule

SynopsisWe found that the XUV excited caffeine undergoes nondadabatic cascade via more than 100 shake-up states within the time constant of 40 fs by using femtosecond XUV-NIR pump-probe photo-ion spectroscopy and the SAC-CI level of ab-initio many-body theory. This nonadiabatic cascade results in the photofragmentation to specific large fragments. Furether ionization by NIR probe during the cascade increases the small fragments CH3 +, CO+ etc. This results show that both vibronic coupling and electron correlation are the keys for the femtochemistry in the highly-correlated electronic excited states.

A spoonful of sugar for your coffee

Drug Solvation Although we brew coffee and tea in water, the psychoactive drug we crave, caffeine, is moderately hydrophobic and becomes more so as the temperature of a beverage decreases. Stacked aggregates of caffeine molecules, which may have different properties, can form at saturation. Shumilin et al. investigated the distribution of caffeine aggregates and monomers in response to increasing concentration of a common excipient: sugar. Although various sugars decreased overall caffeine solubility, they had a preferential effect on oligomers and resulted in a higher relative proportion of caffeine in the monomer form. J. Am. Chem. Soc. 141 , 18056 (2019).

Molecular Interpretation of the Compaction Performance and Mechanical Properties of Caffeine Cocrystals: A Polymorphic Study.

The 1:1 caffeine (CAF) and 3-nitrobenzoic acid (NBA) cocrystal (CAF:NBA) displays polymorphism. Each polymorph shares the same docking synthon that connects individual CAF and NBA molecules within the asymmetric unit; however, the extended intermolecular interactions are significantly different between the two polymorphic modifications. These alternative interaction topologies translate to distinct structural motifs, mechanical properties, and compaction performance. To assist our molecular interpretation of the structure-mechanics-performance relationships for these cocrystal polymorphs, we combine powder Brillouin light scattering (p-BLS) to determine the mechanical properties with energy frameworks calculations to identify potentially available slip systems that may facilitate plastic deformation. The previously reported Form 1 for CAF:NBA adopts a 2D-layered crystal structure with a conventional 3.4 Å layer-to-layer separation distance. For Form 2, a columnar structure of 1D-tapes is displayed with CAF:NBA dimers running parallel to the (110) crystallographic direction. Consistent with the layered crystal structure, the shear modulus for Form 1 is significantly reduced relative to Form 2, and moreover, our p-BLS spectra for Form 1 clearly display the presence of low-velocity shear modes, which support the expectation of a low-energy slip system available for facile plastic deformation. Our energy frameworks calculations confirm that Form 1 displays a favorable slip system for plastic deformation. Combining our experimental and computational data indicates that the structural organization in Form 1 of CAF:NBA improves the compressibility and plasticity of the material, and from our tabletability studies, each of these contributions confers superior tableting performance to that of Form 1. Overall, mechanical and energy framework data permit a clear interpretation of the functional performance of polymorphic solids. This could serve as a robust screening approach for early pharmaceutical solid form selection and development.

Solubility of Caffeine in Supercritical CO2: A Molecular Dynamics Simulation Study.

The extraction of caffeine from green tea leaves and cocoa beans is a common industrial process for the production of decaffeinated beverages and pharmaceuticals. The choice of the solvent critically determines the yield of this extraction process. Being an environmentally benign and recyclable solvent, supercritical carbon dioxide (scCO2) has emerged as the most desirable green solvent for caffeine extraction. The present study investigates the solvation properties of caffeine in scCO2 at two different temperatures (318 and 350 K) using molecular dynamics simulations. Unlike in water, the caffeine molecules in scCO2 do not aggregate to form clusters due to relatively stronger caffeine-CO2 interactions. A well-structured scCO2 solvent shell envelops each caffeine molecule as a result of strong electron-donor-acceptor (EDA) and hydrogen-bonding interactions between these two species. Upon heating, although marginal site-specific changes in the distribution of nearest CO2 around caffeine are observed, the overall distribution is retained. At a higher temperature, the caffeine-CO2 hydrogen-bonding interactions are weakened, while their EDA interactions become relatively stronger. The results underscore the importance of the interplay of these interactions in determining stable solvent structures and solubility of caffeine in scCO2.

PP#69 - Supramolecular interaction of caffeine molecules with each other, water molecules and oxygen atoms in the cobalt, cadmium and magnesium perrhenates of caffeine

PP#69 - Supramolecular interaction of caffeine molecules with each other, water molecules and oxygen atoms in the cobalt, cadmium and magnesium perrhenates of caffeine

Probing the binding selected metal ions and biologically active substances to the antimicrobial peptide LL-37 using DSC, ITC measurements and calculations

Differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC) techniques have been used to describe physicochemical properties of polypeptide LL-37. LL-37 is a 37-residue, amphipathic, helical peptide, the only cathelicidin-derived antimicrobial peptide found in the human organism. Thermal stability of the LL-37 peptide in a water solution was measured by DSC over the 288.15–333.15 K range. Furthermore, the ITC method supported by theoretical calculations (peptide–ligand docking) were used to study the interactions between LL-37 and some divalent metal ions, namely Cu2+, Zn2+, and Ni2+ ions as well as acetylsalicylic acid, ascorbic acid, and caffeine molecules. It has been proven that under experimental conditions, the LL-37 peptide reveals affinity only toward Cu2+ and Zn2+ ions. The stoichiometry, conditional binding constants, logKITC, and thermodynamic parameters (∆ITCG, ∆ITCH, T∆ITCS) of the resulting Cu(II) and Zn(II) complexes were determined and discussed.

Caffeine and taurine slow down water molecules

In this work we study the effect of caffeine and taurine on the mobility of water molecules at 298 K using femtosecond mid-infrared and dielectric relaxation spectroscopy. We observe both molecules to have a slowing down effect on the mobility of surrounding water molecules: a single caffeine molecule slows down ∼9 water molecules, a single taurine molecule slows down ∼4 water molecules. The reorientation time constant of these slow water molecules is 4–5 times longer than the reorientation time constant of 2.5 ps of water molecules in bulk liquid water.

Investigation of caffeine taste mechanism through a statistical physics modeling of caffeine dose-taste response curve by a biological putative caffeine adsorption process in electrophysiological response

This work is a contribution to understand the taste mechanism of caffeine molecule using a modeling of a putative adsorption process by model expressions established by a statistical physics treatment. A physicochemical and a gustative parts are the main constituents of this work. We start with a physicochemical investigation of the adsorption process of caffeine molecule, as adsorbate in liquid phase, onto β-cyclodextrin as adsorbent. Experimental adsorption isotherm curves of caffeine onto β-cyclodextrin coated onto Quartz crystal are carried out at three different temperatures. The Hill model expression with three parameters n, NM and C1/2, established by statistical physics formalism investigated in part I, is the best fitting model of the experimental data. Thermodynamic potential functions that govern the adsorption process, such as entropy, internal energy and Gibbs free enthalpy are investigated. PSD and AED are derived by a steric and energetic derivatives of the Hill model. In part II the same method of fitting is applied to the taste electrophysiological dose-response curve by a caffeine putative adsorption on gustative nerve in caterpillar. All the physicochemical parameters introduced in the fitting Hill model expression, serve first, to analyze the taste mechanism of the bitter caffeine taste. Secondly, all these stereographic and energetic parameters will be considered henceforward for an objective characterization of caffeine molecule taste in both its two aspects, intensive and qualitative aspects of caffeine taste.

DINUCLEAR COPPER(II) ACETATE COMPLEX WITH CAFFEINE, A FAST MECHANOCHEMICAL SYNTHESIS

A new dinuclear paddle-wheel copper(II) complex with caffeine was synthesized by the solvent-based and mechanochemical methods from copper(II) acetate and caffeine in a 1:1 molar ratio. Mechanochemical synthesis was found to be the fastest and easiest way to prepare the complex. The reaction proceeds with addition of small amounts of methanol or ethanol. The complex was characterized by FT-IR spectroscopy, elemental and thermoanalytical methods (TG and DSC) and X-ray diffraction methods. The molecular and crystal structure was determined by the single crystal X-ray diffraction method. The complex molecule consists of a centrosymmetric dinuclear unit, Cu2(-Ac)4(caf)2, with two copper(II) atoms bridged by four acetato groups, and N-coordinated caffeine (caf) molecules in the apical posi-tions.

Zinc(II) and cadmium(II) halide complexes with caffeine: Synthesis, X-ray crystal structure, cytotoxicity and genotoxicity studies

Molecular complexes [Zn(caf)(H2O)I2] (I), [Zn(caf)(H2O)Cl2] (IV), and the polymeric ones {[Cd(H2O)2I2](caf).2H2O}n (II) and {[Cd(H2O)2Br2](caf).2H2O}n (III) consisting of infinite Cd-containing chains with bridging halide ions and water molecules in trans-position and connected with each other due to hydrogen bonding with participation of caffeine (caf) and water molecules, were prepared and characterized by the powder and single crystal X-ray diffraction, IR vibrational spectroscopy, 1H NMR, ESI-MS spectroscopy, thermal analysis and DFT calculations. It was found that the complexes (I) and (IV) are characterized by tetrahedral geometry, the caffeine molecule being coordinated by the central atom via its N9 atom. The preferability of complex formation was evaluated by quantum-chemical calculations. Cyto- and genotoxicity of the compounds have been investigated and discussed in comparison with that of [Zn(AP)2I2] (1) and [Cd(AP)6][Cd(AP)I3]2 (2). It was demonstrated that the prepared complexes, primarily that of cadmium iodide with caffeine (II), are the promising ones for further studies both in vitro and in vivo.

Enhancement of caffeine adsorption on boron nitride fullerene by silicon doping

The physicochemical interaction between undoped- (B24N36; BNF) and silicon-doped boron nitride (B24N35Si; Si-BNF) fullerenes with caffeine was studied in the frame of the density functional theory (DFT). The influence of chemical composition in the capability of the fullerene to interact with caffeine was analyzed in terms of its structural stability, adsorption energy and charge distribution. The obtained results show that caffeine adsorption is enhanced by Si doping. The adsorption energy of caffeine molecule onto the BNF was calculated to be − 0.26 eV, whereas it was − 0.33 eV after doping. This effect is attributed to a rearrangement of the charge density driven by the substitutional defect (SiN). After caffeine adsorption, an electron density displacement from the Si–BNF to the sorbate which stabilizes the caffeine/Si–BNF system is identified. Moreover, Si doping decreases the chemical hardness, while it induces a net spin angular momentum in the fullerene. The magnetic moment of the Si–BNF was determined in 1.0 µB, which does not vanish after caffeine adsorption. The physicochemical parameters of the Si–BNF, along with its magnetic behavior, could favor using it as nanovehicle for drug delivery.

Caffeine interactions with salicylatocopper(II) complexes: Supramolecular structure, spectral properties and DFT study

Four new products of formula [Cu(3-MeSal)2(H2O)2]·2caf (1), [Cu(5-MeSal)2(H2O)4] [Cu(5-MeSal)2(H2O)2]·4caf (2), [Cu(4-MeOSal)2(H2O)2]·2caf·H2O (3), [Cu(5-MeOSal)2(H2O)2]·2caf (4) (where 3-MeSal = 3-methylsalicylate, 5-MeSal = 5-methylsalicylate, 4-MeOSal = 4-methoxysalicylate, 5-MeOSal = 5-methoxysalicylate anion and caf = caffeine) have been characterized by X-ray analysis, EPR, infrared and UV–Vis spectra, as well as elemental analysis. The complex molecules and uncoordinated caffeine molecules are linked through hydrogen bonds into 2D or 3D supramolecular networks. Spectral properties are in good agreement with structural motif. EPR spectra of polycrystalline Cu(II) complexes are of axial symmetry with resolved parallel hyperfine splitting. The composite EPR spectrum is observed in the case of 2 as the result of the presence of two crystallographic copper(II) centers in the crystal structure. Density functional theory calculation of the EPR parameter using three different density functional was performed in order to evaluate molecular g factors for the studied complexes. The calculated values of g tensor are in good qualitative agreement with the parameters derived from the experimental EPR spectra.

Pulse shape and molecular orientation determine the attosecond charge migration in Caffeine

The recent reduction of laser pulse duration down to the attosecond regime offers unprecedented opportunities to investigate ultrafast changes in the electron density before nuclear motion sets in. Here, we investigate the hole dynamics in the Caffeine molecule that is induced by an ionizing XUV pulse of 6 fs duration using the approximate time-dependent density functional theory method TD-DFTB. In order to account for ionization in a localized atomic orbital basis we apply a complex absorbing potential to model the continuum. Propagation of the time-dependent Kohn–Sham equations allows us to extract the time-dependent hole density taking the pulse shape explicitly into account. Results show that the sudden ionization picture, which is often used to motivate an uncorrelated initial state, fails for realistic pulses. We further find a strong dependence of the hole dynamics on the polarization of the laser field. Notwithstanding, we observe fs charge migration between two distant functional groups in Caffeine even after averaging over the molecular orientation.

Caffeine: traditional and new therapeutic indications and use as a dermatological model drug

Coffee consumption had already been described in the 15th century. The spreading of coffee drinking was not only a consequence of its delicious aromatic taste, but also of its pharmacological effects, especially due to its caffeine content. In this review, the mechanisms behind its complex stimulatory effects and the latest studies on the possible new therapeutic indications of caffeine are summarized. Several papers reported the neuroprotective (in Alzheimer's and Parkinson's disease) and hepatoprotective profiles of caffeine, and we show the most promising new results about its preventive properties in dermal malignancies. These findings were described both in cell cultures and in vivo. The application of caffeine and coffee in cosmetology and dermatological products is based on their antioxidant property and on the above-mentioned beneficial effects. Caffeine is also presented here as a dermatological model drug due to its hydrophilic profile. It can be used for designing and comparing different novel drug formulations, although beside the transcellular route, the follicular and transappendageal pathways play also important roles in its skin penetration. Taken together, caffeine molecule has many recently discovered beneficial pharmacological effects, but one should be careful with its excessive consumption. It can result in several adverse events if overdosed and in case of regular intake of high doses, after abandonment, withdrawal symptoms may appear. Orv Hetil. 2018; 159(10): 384-390.