Simultaneous determination of caffeine, theophylline and theobromine in food samples by a kinetic spectrophotometric method

The simultaneous measurement of quaternary mixture in over-the-counter cold medications using sequential spectrophotometric resolution approach enhanced with in-lab sample enrichment

A sequential spectrophotometric resolution technique (SSRT) was developed in this study without the use of systematic separation procedures to determine drug of a quaternary combination; caffeine (CAF), pseudoephedrine (PSE), doxylamine succinate (DOX), and paracetamol (PAR). Their presence in a tablet with a gap ratio of 3:3:1:150, respectively, and their overlapping spectra with low absorptivities make their resolution and determination impossible without prior separation. successive ratio subtraction technique (SRST) and constant multiplication method were used to solve these problems. Furthermore, an in-lab sample enrichment technique was applied to increase minor components concentration and consequently their absorbanses (CAF, PSE, and DOX). The D⁰ absorption spectra were generated by successive ratios followed by subtraction and multiplication of the constants. The maximum absorbances of the drugs tested, namely (CAF, PSE, DOX and PAR) were measured at wavelengths of 272.0, 257.0, 260.0, and 248.0 nm, respectively. The limits of detection (LOD) and limits of quantification (LOQ) were 0.021, 0.124, 0.186, 0.137 and 0.070, 0.414, 0.621, 0.456 (µg/mL), respectively. The linearitiy ranges (µg/mL) were 1.0-22.0, 1.0-24.0, 10.0-90.0 and 1.0-15.0 for CAF, PSE, DOX, and PAR, respectively. The International Conference on Harmonization (ICH) guidelines were applied for method validation, and the results obtained were within the limited parameters. The finding results were compared to official and/or published analytical methods to determine the procedure's reliability. It was noted that there was no actual difference in accuracy and precision between both meyhods. The proposed technique is sensitive, selective and economic;so it can be applied to the simultaneous analysis of these drugs in their commercial tablets and/or in quality-control laboratories.

An overview of bitter compounds in foodstuffs: Classifications, evaluation methods for sensory contribution, separation and identification techniques, and mechanism of bitter taste transduction

The bitter taste is generally considered an undesirable sensory attribute. However, bitter-tasting compounds can significantly affect the overall flavor of many foods and beverages and endow them with various beneficial effects on human health. To better understand the relationship between chemical structure and bitterness, this paper has summarized the bitter compounds in foodstuffs and classified them based on the basic skeletons. Only those bitter compounds that are confirmed by human sensory evaluation have been included in this paper. To develop food products that satisfy consumer preferences, correctly ranking the key bitter compounds in foodstuffs according to their contributions to the overall bitterness intensity is the precondition. Generally, three methods were applied to screen out the key bitter compounds in foods and beverages and evaluate their sensory contributions, including dose-over-threshold factors, taste dilution analysis, and spectrum descriptive analysis method. This paper has discussed in detail the mechanisms and applications of these three methods. Typical procedures for separating and identifying the main bitter compounds in foodstuffs have also been summarized. Additionally, the activation of human bitter taste receptors (TAS2Rs) and the mechanisms of bitter taste transduction are outlined. Ultimately, a conclusion has been drawn to highlight the current problems and propose potential directions for further research.

The Effect of In Vitro Digestion on Matcha Tea (Camellia sinensis) Active Components and Antioxidant Activity

This study investigates the effects of in vitro digestion on the antioxidant activity and release of phenolics, xanthine alkaloids, and L-theanine contents of matcha. It establishes digestibility values between 61.2–65.8%. Considering native matcha, the rutin content (303–479 µg/g) reached higher values than catechin (10.2–23.1 µg/g). Chlorogenic acid (2090–2460 µg/g) was determined as predominant. Rutin, quercetin, ferulic, ellagic, and caffeic acid were the least-released phenolics, and their remaining residues reached 76–84%. Protocatechuic, hydroxybenzoic acid, epigallocatechin, and epigallocatechin-3-gallate were the best-released phenolics, with the remaining residues under 1%. Caffeine, L-theanine, and theobromine contents in native matcha reached 16.1, 9.85, and 0.27 mg/g, respectively. Only caffeine (3.66–5.26 mg/g) and L-theanine (0.09–0.15 mg/g) were monitored in the undigested residue, representing 13 and 0.1% of the remaining part, respectively. A chemiluminescence assay showed that water-soluble antioxidants showed significant antioxidant activity in native matcha, while lipid-soluble compounds showed higher antioxidant activity in the undigested samples. Cinnamic and neochlorogenic acids were determined as the main contributors to the ACW values in the undigested matcha, epicatechin, and quercetin in the ACL fraction. The application of the digestion process reduced the antioxidant activity by more than 94%. SEM has proved specific digestion patterns of in vitro digestibility of matcha.

Evaluation of in silico and in lab sample enrichment techniques for the assessment of challengeable quaternary combination in critical ratio

A comparative study of successive spectrophotometric resolution technique for the simultaneous determination of a challengeable quaternary mixture of Chlorpheniramine maleate (CPM), Pseudoephedrine hydrochloride (PSE), Ibuprofen (IBU) and Caffeine (CAF) is presented, without preliminary physical separation steps. Several successive steps were applied on built-in spectrophotometer software utilizing zero and/or derivative and/or ratio spectra of the studied components. These methods, namely, Dual amplitude difference (DAD) as a novel method, Constant multiplication coupled with spectrum subtraction method (CM-SS), Factorized first derivative coupled with derivative transformation method (FD¹ -DT) and Derivative ratio method (DD¹). The calibration graphs are linear over the concentration range of 10.0-80.0 μg/mL,150.0-900.0 μg/mL, 200.0-1400.0 μg/mL and 3.0-30.0 μg/mL for CPM, PSE, IBU and CAF, respectively. The specificity of suggested methods was studied via laboratory prepared (diverse ratios) mixtures and were successfully applied for Antiflu® capsules' analysis. Moreover, sample enrichment via In Silico (via software of spectrophotometer) and In Lab (via spiking with pure sample) techniques was elected for a pharmaceutical dosage form analysis comprising CPM and PSE as minor components. Accuracy, precision and specificity were between the valid limits. Validation steps were done in accordance with the ICH guidelines. Moreover, statistical comparison was carried out between the obtained and reported results for pure powder form and no significant difference appeared.

Influence of Various Factors on Caffeine Content in Coffee Brews

Coffee brews are one of the most popular drinks. They are consumed for caffeine and its stimulant properties. The study aimed to summarize data on the influence of various factors on caffeine content in brews prepared with different methods. The study was carried out using a literature review from 2010-2020. PubMed and Google Scholar databases were searched. Data on caffeine content was collected by analyzing the following factors: the influence of species, brewing time, water temperature, pressure, degree of roast, grinding degree, water type, water/coffee ratio as well as other factors (such as geographical origin). To sum up, converting caffeine content to 1 L of the brew, the highest content is that of brews prepared in an espresso machine (portafilter), with the amount of 7.5 g of a coffee blend (95% Robusta + 5% Arabica), and water (the volume of coffee brew was 25 mL) at a temperature of 92 °C and a pressure of 7 bar, but the highest content in one portion was detected in a brew of 50 g of Robusta coffee poured with 500 mL of cold water (25 °C) and boiled.

Assessing the flavor of cocoa liquor and chocolate through instrumental and sensory analysis: a critical review

The performance of appropriate instrumental and/or sensory analyses is essential to gain insights into the flavor profile of cocoa products. This three-part review is compiled of an overview of the most commonly used instrumental techniques to study cocoa liquor and chocolate flavor, their perception by a trained panel and the potential relationship between them. Each part is the result of a thorough literature study, principally focusing on the assumptions, features and limitations of these techniques. Reviewing of the literature revealed that cocoa matrix effects and methodology restraints were not always considered when instrumentally analyzing cocoa flavor. With respect to sensory analyses, various studies lacked reporting of accomplished trainings and performance of panelists. Moreover, a discrepancy was noticed in the descriptive flavor lexicon employed. Finally, when linking instrumental and sensory data, linear modeling is regularly applied, which might not always be appropriate. This review paper addresses the challenges associated with flavor assessment, intending to incite researchers to critically study cocoa flavor and apply standardized protocols and procedures.

Determination of 4 psychoactive substances in tea using ultra high performance liquid chromatography combined with the quadrupole time-of-flight mass spectrometry

In this study, a method for the qualification and quantification of 4 psychoactive substances in tea using ultra high performance liquid chromatography coupled with the quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) has been developed. Tea samples were extracted by a 50% (v/v) methanol-water solution, and then separated by an ACQUITY UPLC BEH Shield RP18 column using a binary solvent system by gradient elution. The analytes were determined by Q-TOF/MS in TOFMS and information-dependent acquisition (IDA)-MS/MS mode. The results showed that the mass accuracy error of the 4 psychoactive substances were lower than 5.0 × 10-6, and a good linear relationship was observed in the range of 0.5-500 μg L-1 and correlation coefficient was higher than 0.9990. The LOD was in the range of 0.005-0.020 mg kg-1 and the LOQ was in the range of 0.010-0.040 mg kg-1. The recovery of the method was in range of 80.14-93.25% with spike levels of 0.010-0.400 mg kg-1, and relative standard deviations were lower than 10%. The method was simple, specific and reliable. It has been successfully used for the detection of 4 psychoactive substances in tea samples.

Production of theophylline via aerobic fermentation of pu-erh tea using tea-derived fungi

Background

Caffeine is one of the most abundant methylxanthines in tea, and it remains stable in processing of general teas. In the secondary metabolism of microorganism, theophylline is the main conversion product in caffeine catabolism through demethylation. Microorganisms, involved in the solid-state fermentation of pu-erh tea, have a certain impact on caffeine level. Inoculating an appropriate starter strain that is able to convert caffeine to theophylline would be an alternative way to obtain theophylline in tea. The purpose of this study was to isolate and identify the effective strain converting caffeine to theophylline in pu-erh tea, and discuss the optimal conditions for theophylline production.

Results

Caffeine content was decreased significantly (p < 0.05) and theophylline content was increased significantly (p < 0.05) during the aerobic fermentation of pu-erh tea. Five dominant fungi were isolated from the aerobic fermentation and identified as Aspergillus niger, Aspergillus sydowii, Aspergillus pallidofulvus, Aspergillus sesamicola and Penicillium mangini, respectively. Especially, A. pallidofulvus, A. sesamicola and P. mangini were detected in pu-erh tea for the first time. All isolates except A. sydowii TET-2, enhanced caffeine content and had no significant influence on theophylline content. In the aerobic fermentation of A. sydowii TET-2, 28.8 mg/g of caffeine was degraded, 93.18% of degraded caffeine was converted to theophylline, and 24.60 mg/g of theophylline was produced. A. sydowii PET-2 could convert caffeine to theophylline significantly, and had application potential in the production of theophylline. The optimum conditions of theophylline production in the aerobic fermentation were 1) initial moisture content of 35% (w/w), 2) inoculation quantity of 8%, and 3) incubation temperature at 35 °C.

Conclusions

For the first time, we find that A. sydowii PET-2 could convert caffeine to theophylline, and has the potential value in theophylline production through aerobic fermentation.

Pro-oxidant and lifespan extension effects of caffeine and related methylxanthines in Caenorhabditis elegans

Caffeine and related purine alkaloids are common ingredients of many stimulating drinks. Studies have shown that lower concentrations of caffeine have a protective role in aging-related disorders. However, the associated mode of action of caffeine and its related methylxanthines is still not clear. In this study, we demonstrated that caffeine and theophylline promote longevity in Caenorhabditis elegans. Lifespan studies with the wild type, DAF-16 and SKN-1 mutant strains indicated that the methylxanthines-mediated lifespan extension in C. elegans was independent of DAF-16/FOXO and SKN-1. All the tested methylxanthines could protect C. elegans against acute oxidative stress. At early stages of life, an increase of ROS (reactive oxygen species) induced the translocation of DAF-16 and SKN-1, resulting in upregulation of several antioxidant genes, for example, sod-3p::GFP, gst-4p::GFP, gcs-1p::GFP; and downregulation of hsp-16.2p::GFP. RT-PCR corroborates the upregulation of gst-4 and skn-1 genes. The expression of DAF-16 decreased although its nuclear translocation was induced.

Biodegradation of caffeine by whole cells of tea-derived fungi Aspergillus sydowii, Aspergillus niger and optimization for caffeine degradation

BACKGROUND

Pu-erh tea is a traditional Chinese tea and produced by natural solid-state fermentation. Several studies show that the natural microbiota influence caffeine level in pu-erh tea. Our previous research also found that the caffeine declined significantly (p < 0.05) in the fermentation, which suggested that the caffeine level could be influenced by specific strains. The purpose of this study was to isolate and identify microorganisms for caffeine degradation, and this research explored the degradation products from caffeine and optimal condition for caffeine degradation.

RESULTS

11 Fungi were isolated from pu-erh tea fermentation and 7 strains could survive in caffeine solid medium. Two superior strains were identified as Aspergillus niger NCBT110A and Aspergillus sydowii NRRL250 by molecular identification. In the substrate tests with caffeine, A. niger NCBT110A could use caffeine as a potential carbon source while glucose is absent, A. sydowii NRRL250 could degrade 600 mg/L caffeine completely in a liquid medium. During the degradation product analysis of A. sydowii NRRL250, theophylline and 3-methlxanthine were detected, and the level of theophylline and 3-methlxanthine increased significantly (p < 0.05) with the degradation of caffeine. The single factor analysis showed that the optimum conditions of caffeine degradation were 1) substrate concentration of 1200 mg/L, 2) reaction temperature at 30 °C, and 3) pH of 6. In the submerged fermentation of tea infusion by A. sydowii NRRL250, 985.1 mg/L of caffeine was degraded, and 501.2 mg/L of theophylline was produced.

CONCLUSIONS

Results from this research indicate that Aspergillus sydowii NRRL250 was an effective strain to degrade caffeine. And theophylline and 3-methlxanthine were the main caffeine degradation products.

Pharmacological potential of methylxanthines: Retrospective analysis and future expectations

Methylated xanthines (methylxanthines) are available from a significant number of different botanical species. They are ordinarily included in daily diet, in many extremely common beverages and foods. Caffeine, theophylline and theobromine are the main methylxanthines available from natural sources. The supposedly relatively low toxicity of methylxanthines, combined with the many beneficial effects that have been attributed to these compounds through time, generated a justified attention and a very prolific ground for dedicated scientific reports. Methylxanthines have been widely used as therapeutical tools, in an intriguing range of medicinal scopes. In fact, methylxanthines have been/were medically used as Central Nervous System stimulants, bronchodilators, coronary dilators, diuretics and anti-cancer adjuvant treatments. Other than these applications, methylxanthines have also been hinted to hold other beneficial health effects, namely regarding neurodegenerative diseases, cardioprotection, diabetes and fertility. However, it seems now consensual that toxicity concerns related to methylxanthine consumption and/or therapeutic use should not be dismissed. Taking all the knowledge and expectations on the potential of methylxanthines into account, we propose a systematic look at the past and future of methylxanthine pharmacologic applications, discussing all the promise and anticipating possible constraints. Anyways, methylxanthines will still substantiate considerable meaningful research and discussion for years to come.

Integrating nanohybrid membranes of reduced graphene oxide: chitosan: silica sol gel with fiber optic SPR for caffeine detection

Caffeine is the most popular psychoactive drug consumed in the world for improving alertness and enhancing wakefulness. However, caffeine consumption beyond limits can result in lot of physiological complications in human beings. In this work, we report a novel detection scheme for caffeine integrating nanohybrid membranes of reduced graphene oxide (rGO) in chitosan modified silica sol gel (rGO: chitosan: silica sol gel) with fiber optic surface plasmon resonance. The chemically synthesized nanohybrid membrane forming the sensing route has been dip coated over silver coated unclad central portion of an optical fiber. The sensor works on the mechanism of modification of dielectric function of sensing layer on exposure to analyte solution which is manifested in terms of red shift in resonance wavelength. The concentration of rGO in polymer network of chitosan and silica sol gel and dipping time of the silver coated probe in the solution of nanohybrid membrane have been optimized to extricate the supreme performance of the sensor. The optimized sensing probe possesses a reasonably good sensitivity and follows an exponentially declining trend within the entire investigating range of caffeine concentration. The sensor boasts of an unparalleled limit of detection value of 1.994 nM and works well in concentration range of 0-500 nM with a response time of 16 s. The impeccable sensor methodology adopted in this work combining fiber optic SPR with nanotechnology furnishes a novel perspective for caffeine determination in commercial foodstuffs and biological fluids.

Structure-Bioactivity Relationships of Methylxanthines: Trying to Make Sense of All the Promises and the Drawbacks

Methylxanthines are a group of phytochemicals derived from the purine base xanthine and obtained from plant secondary metabolism. They are unobtrusively included in daily diet in common products as coffee, tea, energetic drinks, or chocolate. Caffeine is by far the most studied methylxanthine either in animal or epidemiologic studies. Theophylline and theobromine are other relevant methylxanthines also commonly available in the aforementioned sources. There are many disseminated myths about methylxanthines but there is increased scientific knowledge to discuss all the controversy and promise shown by these intriguing phytochemicals. In fact, many beneficial physiologic outcomes have been suggested for methylxanthines in areas as important and diverse as neurodegenerative and respiratory diseases, diabetes or cancer. However, there have always been toxicity concerns with methylxanthine (over)consumption and pharmacologic applications. Herein, we explore the structure-bioactivity relationships to bring light those enumerated effects. The potential shown by methylxanthines in such a wide range of conditions should substantiate many other scientific endeavors that may highlight their adequacy as adjuvant therapy agents and may contribute to the advent of functional foods. Newly designed targeted molecules based on methylxanthine structure may originate more specific and effective outcomes.

Characteristics of diprophylline-induced bidirectional modulation on rat jejunal contractility

In this study, we propose that diprophylline exerts bidirectional modulation (BM) on the isolated rat jejunal segment depending on its contractile state. The results supported the hypothesis. Diprophylline (20 µM) exerted stimulatory effects on the contractility of jejunal segment in six low contractile states while inhibitory effects in six high contractile states, showing the characteristics of BM. Diprophylline-induced stimulatory effect was significantly blocked by atropine, indicating the correlation with cholinergic activation. Diprophylline-induced inhibitory effect was partially blocked by phentolamine, propranolol, and L-N-Nitro-Arginine respectively, indicating their correlation with sympathetic activation and nitric oxide-mediated relaxing mechanisms. Diprophylline-induced BM was abolished by tetrodotoxin or in a Ca²⁺ free condition or pretreated with tyrosine kinase inhibitor imatinib, suggesting that diprophylline-induced BM is Ca²⁺ dependent, and that it requires the presence of enteric nervous system as well as pacemaker activity of interstitial cells of Cajal. Diprophylline significantly increased the reduced MLCK expression and myosin extent in constipation-prominent rats and significantly decreased the increased MLCK expression and myosin extent in diarrhea-prominent rats, suggesting that the change of MLCK expression may also be involved in diprophylline-induced BM on rat jejunal contractility. In summary, diprophylline-exerted BM depends on the contractile states of the jejunal segments, requires the presence of Ca²⁺, enteric nervous system, pacemaker activity of interstitial cells of Cajal, and MLCK-correlated myosin phosphorylation. The results suggest the potential implication of diprophylline in relieving alternative hypo/hyper intestinal motility.