Interaction Of Caffeine Research Articles

Impact of chlorogenic acids from coffee on urine metabolome in healthy human subjects

Several studies suggest that coffee has some benefits for health; however, little is known about the specific role of the main polyphenol compounds of coffee, chlorogenic acids (CGAs), without caffeine interaction. A 1H-Nuclear Magnetic Resonance (1H-NMR)-based metabolomics approach was used to assess the effect of CGAs from coffee on the human urine metabolome. Ten male volunteers participated in a dietary crossover randomized intervention study with a rich CGAs coffee extract beverage (CEB: 223mg/100ml of CGAs). The study consisted of a daily intake of CEB or a control beverage with equal caffeine dose during 28days. Fasting urines collected at the first and last days of each period of the study were analyzed using an CGAs untargeted 1H-NMR approach. Additionally, 4-hour postpandrial urines after the first intake of each beverage were also analyzed. Uni- and multi-variate statistic approaches were used to strengthen the results. Multilevel partial least squares discriminant analysis (ML-PLS-DA) was used to paired comparisons across the crossover design. A further univariate analysis model for crossover studies was performed to assess the significant changes. Acute consumption of CEB resulted in high excretion of 2-furoylglycine, likewise endogenous compounds such as succinic, citric, 3-methyl-2-oxovaleric and isobutyric acids. Sustained consumption of CEB showed an increase of microbiota-derived compounds such as hippuric, 3-(3-Hydroxyphenyl)-3-hydroxypropionic and 3-hydroxyhippuric acids in urine. Moreover, trigonelline was found in urine after both acute and sustained intakes, as well as in the composition of the beverage exhibiting a direct excretion of this biomarker without any biotransformation, suggesting a non-interindividual variation.

High Doses of Theanine Improve Visual Stimulus Discrimination in a Dose‐dependent Manner

Theanine is an amino acid found naturally in tea. High doses of theanine, caffeine and their combination improve visual attention and processing. Therefore, we aimed to examine 1) the effects of theanine, caffeine and their combination (TC); 2) the possible interaction of theanine and caffeine and 3) the dose‐response relationship of theanine in improving visual stimulus discrimination (VSD).This study represents an archival analysis of data derived from a primary study in which 200mg of theanine, 160mg of caffeine, TC and distilled water (placebo) were administered orally at least 1 week apart to 20 healthy males (21.9±.7 years) using a crossover design. Recognition visual reaction time was measured before (RVRTB) and 55 minutes after (RVRTA) each administration, using a computer‐based test (SermionTM). In the task, subjects responded to 10 randomly occurring white‐flashes (target‐stimuli) by pressing a button, while ignoring random red‐flashes. Simple visual reaction time (SVRTA) was also measured immediately before RVRTA. In this task, subjects indicated the presence of 10 random white‐flashes (without red‐flash distractor). Post‐dose motor evoked potential latency (MEP; Medtronic KeypointTM, Denmark) after transcranial magnetic stimulation (Magstim 200TM, UK) and P100 visual evoked potential latency (P100; RMSEMG EPMK‐II, India) were recorded sequentially at 35 minutes of substance administration. RVRTA was regressed vs. SVRTA, RVRTB, P100, MEP and substance (model 1). To examine the synergistic effect, RVRTA of theanine, caffeine TC and placebo were regressed vs. respective SVRTA, RVRTB, P100, MEP, 2 dummy coded variables for theanine and caffeine and their interaction (model 2). In another 5‐way crossover, 12.5, 25, 50, 100 and 200mg of theanine were administered at least 3 days apart to 5 subjects to assess RVRTB, RVRTA and SVRTA. RVRTA of this study was regressed vs. RVRTB, SVRTA and dose (model 3). All procedures were in accord with the Helsinki Declaration and were approved by the IRB at Faculty of Medicine, Peradeniya.Model 1 (R2=.41, p<.001) suggested that when RVRTB, SVRTA, P100 and MEP were constant, compared to the placebo, theanine and TC significantly reduced RVRTA by 25.86ms (t=−2.3, p=.025) and 35.84ms (t=−3.1, p=.002) respectively. Caffeine had a trend of improvement (β=22.5ms, t=−1.9, p=.051). Model 2 (R2=.35, p<.001) revealed a significant effect for theanine (p=.030) and a trend for caffeine (p=.070) but not for the interaction (p=.46). Model 3 (R2=.50, p=.002) indicated that when controlled for SVRTA and RVRTB, increasing theanine dose by 1mg reduced RVRTA by 0.28ms (t=−3.02, p=.007).Thus, when controlled for visual and motor conduction and simple stimulus processing latencies, theanine and TC seem to improve VSD. Effects of theanine and caffeine appear to be additive rather than synergistic. Improvement of VSD by theanine seems to be dose‐dependent.Support or Funding InformationNational Research Council, Sri Lanka (Grant 09‐32), International Research Center, University of Peradeniya, Sri Lanka.

Acute effects of theanine, caffeine and theanine–caffeine combination on attention

Objective: l-theanine is a constituent of tea which is claimed to enhance cognitive functions. We aimed to determine whether theanine and theanine–caffeine combination have acute positive effects on cognitive and neurophysiological measures of attention, compared to caffeine (a positive control) and a placebo in healthy individuals.Design: In a placebo-controlled, five-way crossover trial in 20 healthy male volunteers, we compared the effects of l-theanine (200 mg), caffeine (160 mg), their combination, black tea (one cup) and a placebo (distilled water) on cognitive (simple [SVRT] and recognition visual reaction time [RVRT]) and neurophysiological (event-related potentials [ERPs]) measures of attention. We also recorded visual (VEPs) and motor evoked potentials (MEPs) to examine any effects of treatments on peripheral visual and motor conduction, respectively.Results: Mean RVRT was significantly improved by theanine (P = 0.019), caffeine (P = 0.043), and theanine–caffeine combination (P = 0.001), but not by tea (P = 0.429) or placebo (P = 0.822). VEP or MEP latencies or SVRT did not show significant inter-treatment differences. Theanine (P = 0.001) and caffeine (P = 0.001) elicited significantly larger mean peak-to-peak N2-P300 ERP amplitudes than the placebo, whereas theanine–caffeine combination elicited a significantly larger mean N2-P300 amplitude than placebo (P < 0.001), theanine (P = 0.029) or caffeine (P = 0.005). No significant theanine × caffeine interaction was observed for RVRT or N2-P300 amplitude.Discussion: A dose of theanine equivalent of eight cups of back tea improves cognitive and neurophysiological measures of selective attention, to a degree that is comparable with that of caffeine. Theanine and caffeine seem to have additive effects on attention in high doses.

Chronic caffeine produces sexually dimorphic effects on amphetamine-induced behavior, anxiety and depressive-like behavior in adolescent rats

Caffeine consumption has been increasing rapidly in adolescents; however, most research on the behavioral effects of caffeine has been conducted in adults. Two experiments were conducted in which adolescent male and female rats were treated with a moderate dose of caffeine (0.25g/l) in their drinking water beginning on P26–28. In the first experiment, animals were maintained on caffeinated drinking water or normal tap water for 14days and were then tested for behavioral and striatal c-Fos response to amphetamine (1.5mg/kg). In the second experiment, rats were maintained on caffeinated drinking water or normal tap water beginning on P28 and were tested for novel object recognition, anxiety in the light/dark test (L/D) and elevated plus maze (EPM), and depressive like behavior in the forced swim test (FST) beginning on the 14th day of caffeine exposure. Caffeine decreased amphetamine-induced rearing in males, but had no effect in females; however, this behavioral effect was not accompanied by changes in striatal c-Fos, which was increased by amphetamine but not altered by caffeine. No effects of caffeine were observed on novel object recognition or elevated plus maze behavior. However, in the L/D test, there was a sex by caffeine interaction on time spent in the light driven by a caffeine-induced increase in light time in the males but not the females. On the pretest day of the FST, sex by caffeine interactions were observed for swimming and struggling; caffeine decreased struggling behavior and increased swimming behavior in males and caffeine-treated females demonstrated significantly more struggling and significantly less swimming than caffeine-treated males. A similar pattern was observed on the test day in which caffeine decreased immobility overall and increased swimming. These data reveal sex dependent effects of caffeine on behavior in adolescent rats.

Binding of caffeine with caffeic acid and chlorogenic acid using fluorescence quenching, UV/vis and FTIR spectroscopic techniques.

The interactions of caffeine (CF) with chlorogenic acid (CGA) and caffeic acid (CFA) were investigated by fluorescence quenching, UV/vis and Fourier transform infrared (FTIR) spectroscopic techniques. The results of the study indicated that the fluorescence quenching between caffeine and hydroxycinnamic acids could be rationalized in terms of static quenching or the formation of non-fluorescent CF-CFA and CF-CGA complexes. From fluorescence quenching spectral analysis, the quenching constant (KSV), quenching rate constant (kq), number of binding sites (n), thermodynamic properties and conformational changes of the interaction were determined. The quenching constants (KSV) between CF and CGA, CFA are 1.84 × 10(4) and 1.04 × 10(4) L/mol at 298 K and their binding site n is ~ 1. Thermodynamic parameters determined using the Van't Hoff equation indicated that hydrogen bonds and van der Waal's forces have a major role in the reaction of caffeine with caffeic acid and chlorogenic acid. The 3D fluorescence, UV/vis and FTIR spectra also showed that the binding of CF with CFA and CGA induces conformational changes in CFA and CGA.

Interaction of caffeine with the SOS response pathway in Escherichia coli.

BackgroundPrevious studies have highlighted the antimicrobial activity of caffeine, both individually and in combination with other compounds. A proposed mechanism for caffeine’s antimicrobial effects is inhibition of bacterial DNA repair pathways. The current study examines the influence of sub-lethal caffeine levels on the growth and morphology of SOS response pathway mutants of Escherichia coli.MethodsGrowth inhibition after treatment with caffeine and methyl methane sulfonate (MMS), a mutagenic agent, was determined for E. coli mutants lacking key genes in the SOS response pathway. The persistence of caffeine’s effects was explored by examining growth and morphology of caffeine and MMS-treated bacterial isolates in the absence of selective pressure.ResultsCaffeine significantly reduced growth of E. coli recA- and uvrA-mutants treated with MMS. However, there was no significant difference in growth between umuC-isolates treated with MMS alone and MMS in combination with caffeine after 48 h of incubation. When recA-isolates from each treatment group were grown in untreated medium, bacterial isolates that had been exposed to MMS or MMS with caffeine showed increased growth relative to controls and caffeine-treated isolates. Morphologically, recA-isolates that had been treated with caffeine and both caffeine and MMS together had begun to display filamentous growth.ConclusionsCaffeine treatment further reduced growth of recA- and uvrA-mutants treated with MMS, despite a non-functional SOS response pathway. However, addition of caffeine had very little effect on MMS inhibition of umuC-mutants. Thus, growth inhibition of E. coli with caffeine treatment may be driven by caffeine interaction with UmuC, but also appears to induce damage by additional mechanisms as evidenced by the additive effects of caffeine in recA- and uvrA-mutants.

The influence of caffeine on the activity of moclobemide, venlafaxine, bupropion and milnacipran in the forced swim test in mice.

Worrying data indicate that excessive caffeine intake applies to patients suffering from mental disorders, including depression. It is thus possible to demonstrate the usefulness of caffeine and its derivatives in the treatment of depression. The main goal of the present studywas to evaluate the influence of caffeine (5mg/kg) on the activity of moclobemide (1.5 mg/kg), venlafaxine (1 mg/kg), bupropion (10 mg/kg), and milnacipran (1.25 mg/kg). Moreover, we assessed the influence of caffeine on their serum and brain levels using highperformance liquid chromatography. The experiment was carried out on naïve adult male Albino Swiss mice. Caffeine and tested drugs were administered intraperitoneally. The influence of caffeine on the activity of selected antidepressant drugs was evaluated in forced swim test (FST). Locomotor activity was estimated to verify and exclude false positive/negative results. To assess the influence of caffeine on the levels of studied antidepressant drugs, their concentrations were determined in murine serum and brains using high-performance liquid chromatography. Caffeine potentiated activity of all antidepressants examined in FST and the observed effects were not due to the increase in locomotor activity in the animals. Only in the case of co-administration of caffeine and milnacipran an increased milnacipran concentration in serum was observed without affecting its concentration in the brain. Caffeine potentiates the activity of antidepressant drugs from different chemical groups. The interactions of caffeine with venlafaxine, bupropion and moclobemide occur in pharmacodynamic phase, whereas the interaction of caffeine–milnacipran occurs, at least partially, in pharmacokinetic phase.

Caffeine: cognitive and physical performance enhancer or psychoactive drug?

Caffeine use is increasing worldwide. The underlying motivations are mainly concentration and memory enhancement and physical performance improvement. Coffee and caffeine-containing products affect the cardiovascular system, with their positive inotropic and chronotropic effects, and the central nervous system, with their locomotor activity stimulation and anxiogenic-like effects. Thus, it is of interest to examine whether these effects could be detrimental for health. Furthermore, caffeine abuse and dependence are becoming more and more common and can lead to caffeine intoxication, which puts individuals at risk for premature and unnatural death. The present review summarizes the main findings concerning caffeine’s mechanisms of action (focusing on adenosine antagonism, intracellular calcium mobilization, and phosphodiesterases inhibition), use, abuse, dependence, intoxication, and lethal effects. It also suggests that the concepts of toxic and lethal doses are relative, since doses below the toxic and/or lethal range may play a causal role in intoxication or death. This could be due to caffeine’s interaction with other substances or to the individuals' preexisting metabolism alterations or diseases.

NMR Studies of Hetero-Association of Caffeine with di-O-Caffeoylquinic Acid Isomers in Aqueous Solution.

Caffeine hetero-association with 3,5-di-O-caffeoylquinic acid, 3,4-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid in aqueous solution has been investigated by one-dimensional (1D) and two-dimensional (2D) high resolution 1H and 13C NMR spectroscopy. Self-association of the di-O-caffeoylquinic acid isomers has been studied as well. Caffeine-di-O-caffeoylquinic acid isomers association constants were measured. The value of the association constant of the caffeine-di-O-caffeoylquinic acid complexes is compatible with previous studies and within the typical range of reported association constants for other caffeine-polyphenols complexes. Structural features of the three different complexes have also been investigated by NMR spectroscopy combined with quantum chemical calculations, and the complex conformation is discussed. Our results show that stacking interactions drive the formation of the complexes and that multiple equilibria are present in the interaction of caffeine with 3,4-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid while the complex with 3,5-di-O-caffeoylquinic acid seems to be better defined.Electronic supplementary materialThe online version of this article (doi:10.1007/s11483-014-9368-x) contains supplementary material, which is available to authorized users.

Caffeine interaction with glutamate receptor gene GRIN2A: Parkinson's disease in Swedish population.

A complex interplay between genetic and environmental factors is thought to be involved in the etiology of Parkinson's disease (PD). A recent genome-wide association and interaction study (GWAIS) identified GRIN2A, which encodes an NMDA-glutamate-receptor subunit involved in brain's excitatory neurotransmission, as a PD genetic modifier in inverse association with caffeine intake. Here in, we attempted to replicate the reported association of a single nucleotide polymorphism, GRIN2A_rs4998386, and its interaction with caffeine intake with PD in patient-control study in an ethnically homogenous population in southeastern Sweden, as consistent and independent genetic association studies are the gold standard for the validation of genome-wide association studies. All the subjects (193 sporadic PD patients and 377 controls) were genotyped, and the caffeine intake data was obtained by questionnaire. We observed an association between rs4998386 and PD with odds ratio (OR) of 0.61, 95% confidence intervals (CI) of 0.39–0.96, p = 0.03, under a model excluding rare TT allele. There was also a strong significance in joint effects of gene and caffeine on PD risk (TC heavy caffeine vs. CC light caffeine: OR = 0.38, 95%CI = [0.20–0.70], p = 0.002) and gene-caffeine interaction (OR = 0.998, 95%CI = [0.991–0.999], p<0.001). Overall, our results are in support of the findings of the GWAIS and provided additional evidence indicating PD protective effects of coffee drinking/caffeine intake as well as the interaction with glutamate receptor genotypes.

Moderate swimming exercise and caffeine supplementation reduce the levels of inflammatory cytokines without causing oxidative stress in tissues of middle-aged rats

The levels of circulatory inflammatory markers, including interleukin (IL) IL-1β, IL-6, tumor necrosis factor-α (TNF-α) and interferon (INF-γ), are known to increase associated to aging. Caffeine has been reported to produce many beneficial effects for health. Exercise is considered to be a safe medicine to attenuate inflammation and cellular senescence. The purpose of the present study was to investigate the effects of a moderate-intensity swimming exercise (3 % of body weight, 20 min per day, 4 weeks) and sub-chronic supplementation with caffeine (30 mg/kg, 4 weeks) on the serum cytokine levels in middle-aged (18 months) Wistar rats. The effects of swimming exercise and caffeine on oxidative stress in muscle and liver of middle-aged rats were also investigated. The two-way ANOVA of pro-inflammatory cytokine levels demonstrated a significant exercise x caffeine interaction for IL-1β (F (1, 16) = 9.5772; p = 0.0069), IL-6 (F (1, 16) = 8.0463; p = 0.0119) and INF-γ (F (1, 16) = 15.078; p = 0.0013). The two-way ANOVA of TNF-α levels revealed a significant exercise × caffeine interaction (F (1, 16) = 9.6881; p = 0.00670). Swimming exercise and caffeine supplementation increased the ratio of reduced glutathione/oxidized glutathione in the rat liver and gastrocnemius muscle. Hepatic and renal markers of damage were not modified. In conclusion, a moderate-intensity swimming exercise protocol and caffeine supplementation induced positive adaptations in modulating cytokine levels without causing oxidative stress in muscle and liver of middle-aged rats.

Effect of phosphate buffer on the complexation and photochemical interaction of riboflavin and caffeine in aqueous solution: A kinetic study

A study of the photodegradation of 5 × 10−5 M riboflavin (RF) in 0.2–1.0 M phosphate buffer in the presence and absence of 2.50 × 10−4 M caffeine at pH 6.0–8.0 has been carried out. RF in phosphate buffer is photodegraded simultaneously by normal photolysis (photoreduction) and photoaddition reactions giving rise to lumichrome (LC) and cyclodehydroriboflavin (CDRF) as the main final products, respectively. RF and its photoproducts, formylmethylflavin (FMF), lumiflavin (LF), LC and CDRF in degraded solution have been determined by a specific multicomponent spectrophotometric method with an accuracy of ±5%. The apparent first-order rate constants for the photodegradation of RF and for the formation of LC and CDRF are 5.47–15.05 × 10−3 min−1, 1.06–8.30 × 10−3 min−1 and 4.31–8.05 × 10−3 min−1, respectively. An increase in phosphate concentration leads to an increase in the rate of formation of CDRF and alters the photodegradation of RF in favor of the photoaddition reaction. This photoaddition reaction is further enhanced in the presence of caffeine which results in a further decrease of the fluorescence of RF in phosphate buffer. Caffeine may facilitate the photoaddition reaction by suppression of the photoreduction pathway of RF.

The interactions of caffeine with monoamine oxidase

AimsCaffeine has been used as a scaffold for the design of inhibitors of monoamine oxidase (MAO) A and B. Substitution at the C8 position with a variety of moieties yields structures with high MAO inhibition potencies. Although the MAO inhibitory properties of numerous caffeine derivatives have been characterized, the possibility that caffeine inhibits the MAOs has not been investigated in detail. Based on the therapeutic applications and potential adverse effects of MAO inhibition, this study examines the interactions of caffeine with the MAOs. Main methodsEmploying the recombinant human enzymes, the potencies by which caffeine inhibits the in vitro catalytic activities of the MAOs were recorded and expressed as the IC50 and Ki values. The reversibility of inhibition was determined by measuring the recovery of enzyme activity after dialysis of enzyme–caffeine mixtures. Key findingsCaffeine acts as a MAO inhibitor with Ki values of 0.70mM and 3.83mM for the inhibition of MAO-A and MAO-B, respectively. The results show that caffeine binds reversibly and competitively to both MAO enzymes. SignificanceAlthough structural modifications of caffeine lead to highly potent MAO inhibitors, caffeine is a weak inhibitor of MAO-A and MAO-B. At plasma concentrations (approximately 1–10μM) achieved by normal human consumption, the MAO inhibitory potencies of caffeine are unlikely to be of pharmacological relevance in humans. The MAO inhibitory effects of caffeine should however be taken into consideration when using this drug in vitro and in tissue culture experiments where higher doses and concentrations of caffeine are often used.

Calcium and caffeine interaction in increased calcium balance in ovariectomized rats

OBJECTIVE: This study investigated the effects of caffeine intake associated with inadequate or adequate calcium intake in laparotomized or ovariectomized rats by means of the calcium balance. Forty adults Wistar rats were ovariectomized or laparotomized. METHODS: The animals (n=40) were randomly placed in eight groups receiving the AIN-93 diet with 100% or 50% of the recommended calcium intake with or without added caffeine (6mg/kg/day). The animals were kept in individuals metabolic cages at a temperature of 24°±2ºC, light/dark cycles of 12/12 hours, and deionized water available ad libitum. On the 8th week of the experiment, food consumption was measured and 24-hour urine and 4-day feces were collected to determine calcium balance [Balance=Ca intake-(Urinary Ca+Fecal Ca)]. RESULTS: Animals with adequate calcium intake presented higher balances and rates of calcium absorption and retention (p&lt;0.05) than those with inadequate calcium intake, regardless of caffeine intake (p&lt;0.05). Caffeine intake did not affect urinary calcium excretion but increased balance (p&lt;0.05) in the groups with adequate calcium intake. CONCLUSION: Adequate calcium intake attenuated the negative effects of estrogen deficiency and improved calcium balance even in the presence of caffeine.

Effects of the Interaction of Caffeine and Water on Voice Performance

The objective of this pilot investigation was to study the effects of the interaction of caffeine and water intake on voice as evidenced by acoustic and aerodynamic measures, to determine whether ingestion of 200 mg of caffeine and various levels of water intake have an impact on voice. The participants were 48 females ranging in age from 18 to 35 years who self-reported normal vocal production and were tested following a protocol that included recording weight and height, as well as menstrual cycle phase identification. Results revealed that statistically significant changes were not apparent in any of the voice acoustic or aerodynamic measures across the four groups. These results suggest that 200 mg of caffeine may not degrade vocal acoustics and aerodynamics, and that the interaction of 200 mg of caffeine and water hydration may not lead to statistically significant changes. Further investigation regarding the effects of caffeine and water interaction on voice should examine thresholds of acoustic and aerodynamic measurable responses, particularly by involving increasingly higher levels of caffeine.

Thermodynamics and Kinetics of Cyanidin 3-Glucoside and Caffeine Copigments

The multiequilibrium system of reactions of cyanidin 3-glucoside at acidic and mildly acidic pH values was studied in the presence of caffeine as a copigment. The thermodynamic and kinetic constants were determined using the so-called direct and reverse pH jump experiments that were followed by conventional UV-vis spectroscopy or stopped flow coupled to a UV-vis detector, depending on the rate of the monitored process. Compared with that of free anthocyanin, the copigmentation with caffeine extends the domain of the flavylium cation up to less acidic pH values, while in a moderately acidic medium, the quinoidal base becomes more stabilized. As a consequence, the hydration to give the colorless hemiketal is difficult over the entire range of pH values. At pH 1, two adducts were found for the flavylium cation-caffeine interaction, with stoichiometries of 1:1 and 1:2 and association constants of 161 M⁻¹ (K₁) and 21 M⁻¹ (K₂), respectively.

Liposomes for Topical Use: A Physico-Chemical Comparison of Vesicles Prepared from Egg or Soy Lecithin

Developments in nanotechnology and in the formulation of liposomal systems provide the opportunity for cosmetic dermatology to design novel delivery systems. Determination of their physico-chemical parameters has importance when developing a nano-delivery system. The present study highlights some technological aspects/characteristics of liposomes formulated from egg or soy lecithins for topical use. Alterations in the pH, viscosity, surface tension, and microscopic/macroscopic appearance of these vesicular systems were investigated. The chemical composition of the two types of lecithin was checked by mass spectrometry. Caffeine, as a model molecule, was encapsulated into multilamellar vesicles prepared from the two types of lecithin: then zeta potential, membrane fluidity, and encapsulation efficiency were compared. According to our observations, samples prepared from the two lecithins altered the pH in opposite directions: egg lecithin increased it while soy lecithin decreased it with increased lipid concentration. Our EPR spectroscopic results showed that the binding of caffeine did not change the membrane fluidity in the temperature range of possible topical use (measured between 2 and 50 °C). Combining our results on encapsulation efficiency for caffeine (about 30% for both lecithins) with those on membrane fluidity data, we concluded that the interaction of caffeine with the liposomal membrane does not change the rotational motion of the lipid molecules close to the head group region. In conclusion, topical use of egg lecithin for liposomal formulations can be preferred if there are no differences in the physico-chemical properties due to the encapsulated drugs, because the physiological effects of egg lecithin vesicles on skin are significantly better than that of soy lecithin liposomes.

Fluorescence sensing of caffeine in aqueous solution with carbazole-based probe and imaging application in live cells

The host–guest interaction of caffeine in aqueous solutions has been achieved by using carbazole based imino-phenol receptors with oxopurines influences their fluorescence properties and can be exploited for ‘turn-ON’ fluorescence sensing of caffeine. This new fluorescent probe with high sensitivity and selectivity for detection and first time imaging of caffeine in living cells was developed in aqueous media.

A ratiometric fluorescence sensor for caffeine

The dye disodium 3,4:3',4'-bibenzo[b]thiophene-2,2'-disulfonate can be used as a molecular probe for the fluorimetric detection of caffeine in aqueous solution. The fluorescence response is attributed to non-covalent interactions of caffeine with the dye in the ground state and in the excited state. The bimodal interaction allows performing ratiometric measurements with very good selectivity over structurally related analytes. The dye was also used to develop a simple test strip for the visual differentiation of normal and decaffeinated coffee with a standard UV lamp.

Revealing of pharmacokinetic peculiarities of surface active drug promethazine in its interaction with caffeine in rabbits

The interaction of caffeine and promethazine in rabbits has been investigated. The drugs were administered as single oral doses (200mg caffeine and 100mg promethazine) as well as simultaneously with an interval of 15min. The sequence of administration of the drugs was varied.The influence of caffeine on the pharmacokinetics of promethazine is expressed by: (a) strong increase of Cmax, AUC, AUMC and MRT of promethazine; (b) decreasing of kel, CL and Vss of promethazine. Significant changes are also observed in the pharmacokinetics of caffeine under the influence of promethazine. Besides these changes are depending on the sequence of administration of drugs. The values of Cmax, AUC, AUMC and MRT are reduced, but values of kel, CL and Vss occur when promethazine enters first and then caffeine. In contrast to this, the values of Cmax, AUC and AUMC increase, CL and Vss decrease, but values of MRT and kel remain practically unchanged in case when caffeine was administered first and then promethazine.This nontrivial interaction of drugs may be stipulated by formation of sufficiently stable complexes of promethazine and caffeine in small intestine. It is probable that the structure and properties of these complexes are different in various mixtures and are depending on the sequence of administration of drugs. The presystem elimination of caffeine is enhanced, but first-pass effect of promethazine is suppressed in complex when promethazine enters first. The first-pass effect in complex is suppressed for both drugs when caffeine is administered first and then promethazine.