The Medicinal Chemistry of Caffeine

Multidisciplinary approach combining food metabolomics and epidemiology identifies meglutol as an important bioactive metabolite in tempe, an Indonesian fermented food

This study introduces a multidisciplinary approach to investigate bioactive food metabolites often overlooked due to their low concentrations. We integrated an in-house food metabolite library (n = 494), a human metabolite library (n = 891) from epidemiological studies, and metabolite pharmacological databases to screen for food metabolites with potential bioactivity. We identified six potential metabolites, including meglutol (3-hydroxy-3-methylglutarate), an understudied low-density lipoprotein (LDL)-lowering compound. We further focused on meglutol as a case study to showcase the range of characterizations achievable with this approach. Green pea tempe was identified to contain the highest meglutol concentration (21.8 ± 4.6 mg/100 g). Furthermore, we identified a significant cross-sectional association between plasma meglutol (per 1-standard deviation) and lower LDL cholesterol in two Hispanic adult cohorts (n = 1,628) (β [standard error]: -5.5 (1.6) mg/dl, P = 0.0005). These findings highlight how multidisciplinary metabolomics can serve as a systematic tool for discovering and enhancing bioactive metabolites in food, such as meglutol, with potential applications in personalized dietary approaches for disease prevention.

Emerging phosphodiesterase inhibitors for treatment of neurodegenerative diseases

Neurodegenerative diseases (NDs) cause progressive loss of neuron structure and ultimately lead to neuronal cell death. Since the available drugs show only limited symptomatic relief, NDs are currently considered as incurable. This review will illustrate the principal roles of the signaling systems of cyclic adenosine and guanosine 3',5'-monophosphates (cAMP and cGMP) in the neuronal functions, and summarize expression/activity changes of the associated enzymes in the ND patients, including cyclases, protein kinases, and phosphodiesterases (PDEs). As the sole enzymes hydrolyzing cAMP and cGMP, PDEs are logical targets for modification of neurodegeneration. We will focus on PDE inhibitors and their potentials as disease-modifying therapeutics for the treatment of Alzheimer's disease, Parkinson's disease, and Huntington's disease. For the overlapped but distinct contributions of cAMP and cGMP to NDs, we hypothesize that dual PDE inhibitors, which simultaneously regulate both cAMP and cGMP signaling pathways, may have complementary and synergistic effects on modifying neurodegeneration and thus represent a new direction on the discovery of ND drugs.

Eye Diseases: When the Solution Comes from Plant Alkaloids

Plants are an incredible source of metabolites showing a wide range of biological activities. Among these, there are the alkaloids, which have been exploited for medical purposes since ancient times. Nowadays, many plant-derived alkaloids are the main components of drugs used as therapy for different human diseases. This review deals with providing an overview of the alkaloids used to treat eye diseases, describing the historical outline, the plants from which they are extracted, and the clinical and molecular data supporting their therapeutic activity. Among the different alkaloids that have found application in medicine so far, atropine and pilocarpine are the most characterized ones. Conversely, caffeine and berberine have been proposed for the treatment of different eye disorders, but further studies are still necessary to fully understand their clinical value. Lastly, the alkaloid used for managing hypertension, reserpine, has been recently identified as a potential drug for ameliorating retinal disorders. Other important aspects discussed in this review are different solutions for alkaloid production. Given that the industrial production of many of the plant-derived alkaloids still relies on extraction from plants, and the chemical synthesis can be highly expensive and poorly efficient, alternative methods need to be found. Biotechnologies offer a multitude of possibilities to overcome these issues, spanning from genetic engineering to synthetic biology for microorganisms and bioreactors for plant cell cultures. However, further efforts are needed to completely satisfy the pharmaceutical demand.

Elimination of Toxic Solvents from Analytical Methods in Food Analysis: Caffeine Determination in Tea as an Example

This study presents an innovative method for caffeine determination in tea, employing ethanol as the sole organic solvent for both SPE sample preparation and chromatographic analysis. This approach aligns with green chemistry principles, as confirmed by a comparative study highlighting ethanol's safety and eco-friendliness compared to traditional solvents. The experiments validate ethanol's efficacy in caffeine extraction and chromatographic analysis, minimizing environmental impact and eliminating toxicity risks. Utilizing a reduced chromatography column enhances the method's efficiency and sustainability, resulting in a low limit of quantitation (0.125 μg/mL) and good reproducibility (RSD < 2.5%). Based on tea from the Polish market, the findings reveal the caffeine content (19.29-37.69 mg/g) and endorse ethanol's role in enhancing sustainable chemical analysis in food science.

Greening up organic reactions with caffeine: applications, recent developments, and future directions

Numerous studies in the field of alkaloid chemistry have provided researchers with valuable insights into their unique properties as catalysts. Among the diverse natural catalysts, caffeine has emerged as a green, expedient, and biodegradable catalyst with high efficiency and applicability. Interest in using caffeine as a catalyst has burgeoned over the past few years with its role in diverse multicomponent reactions. Preparation of its imidazolium salts and further conversion to Nitrogen Heterocyclic Carbene (NHC) ligands and ionic liquids offers new paradigms. Caffeine has also played a multifaceted role as a support material in influencing the structural properties of nanoparticles. We hope that the chemistry of caffeine and its applications for sustainable organic transformations discussed in this review will stimulate new thinking and open new avenues in this field.

Prodrugs as empowering tools in drug discovery and development: recent strategic applications of drug delivery solutions to mitigate challenges associated with lead compounds and drug candidates

The delivery of a drug to a specific organ or tissue at an efficacious concentration is the pharmacokinetic (PK) hallmark of promoting effective pharmacological action at a target site with an acceptable safety profile. Sub-optimal pharmaceutical or ADME profiles of drug candidates, which can often be a function of inherently poor physicochemical properties, pose significant challenges to drug discovery and development teams and may contribute to high compound attrition rates. Medicinal chemists have exploited prodrugs as an informed strategy to productively enhance the profiles of new chemical entities by optimizing the physicochemical, biopharmaceutical, and pharmacokinetic properties as well as selectively delivering a molecule to the site of action as a means of addressing a range of limitations. While discovery scientists have traditionally employed prodrugs to improve solubility and membrane permeability, the growing sophistication of prodrug technologies has enabled a significant expansion of their scope and applications as an empowering tool to mitigate a broad range of drug delivery challenges. Prodrugs have emerged as successful solutions to resolve non-linear exposure, inadequate exposure to support toxicological studies, pH-dependent absorption, high pill burden, formulation challenges, lack of feasibility of developing solid and liquid dosage forms, first-pass metabolism, high dosing frequency translating to reduced patient compliance and poor site-specific drug delivery. During the period 2012-2022, the US Food and Drug Administration (FDA) approved 50 prodrugs, which amounts to 13% of approved small molecule drugs, reflecting both the importance and success of implementing prodrug approaches in the pursuit of developing safe and effective drugs to address unmet medical needs.

Advances in targeting Phosphodiesterase 1: From mechanisms to potential therapeutics

Phosphodiesterase 1 (PDE1) is an enzyme entrusted with the hydrolysis of the second messengers cAMP and cGMP, thereby governing a plethora of metabolic processes, encompassing ion channel modulation and cellular apoptosis. Recent advancements in the realm of small molecule structural variations have greatly facilitated the exploration of innovative applications for PDE1. Remarkably, a recent series of PDE1 inhibitors (PDE1i) have been meticulously formulated and devised, showcasing enhanced selectivity and potency. Among them, ITI-214 has entered Phase II clinical trials, holding promise for the treatment of Parkinson's disease and heart failure. Nevertheless, the majority of current PDE1 inhibitors have encountered substantial side effects in clinical trials attributable to their limited selectivity, this predicament presents a formidable obstacle in the development of specific small molecule inhibitors targeting PDE1. This Perspective endeavors to illuminate the potential design approaches, structure-activity relationships, and biological activities of current PDE1i, aiming to offer support and insights for clinical practice and the development of novel PDE1i.

Nanoemulsion Improves the Anti-Inflammatory Effect of Intraperitoneal and Oral Administration of Carvacryl Acetate

Carvacryl acetate (CA) is a monoterpene obtained from carvacrol, which exhibits anti-inflammatory activity. However, its low solubility in aqueous media limits its application and bioavailability. Herein, we aimed to develop a carvacryl acetate nanoemulsion (CANE) and assess its anti-inflammatory potential in preclinical trials. The optimized nanoemulsion was produced by ultrasound, and stability parameters were characterized for 90 days using dynamic light scattering after hydrophilic-lipophilic balance (HLB) assessment. To evaluate anti-inflammatory activity, a complete Freund's adjuvant-induced inflammation model was established. Paw edema was measured, and local interleukin (IL)-1β levels were quantified using ELISA. Toxicity was assessed based on behavioral changes and biochemical assays. The optimized nanoemulsion contained 3% CA, 9% surfactants (HLB 9), and 88% water and exhibited good stability over 90 days, with no signs of toxicity. The release study revealed that CANE followed zero-order kinetics. Dose-response curves for CA were generated for intraperitoneal and oral administration, demonstrating anti-inflammatory effects by both routes; however, efficacy was lower when administered orally. Furthermore, CANE showed improved anti-inflammatory activity when compared with free oil, particularly when administered orally. Moreover, daily treatment with CANE did not induce behavioral or biochemical alterations. Overall, these findings indicate that nanoemulsification can enhance the anti-inflammatory properties of CA by oral administration.

Anti-obesity effects of chlorogenic acid and caffeine- lipid nanoparticles through PPAR-γ/C/EBP-ɑ pathways

Obesity is considered one of the most crucial health problems of the century. Therefore, reducing obesity is critically important. Caffeine (CF) and chlorogenic acid (CLA), which are substantial components in green bean coffee which maximize thermogenesis in brown adipose tissue. In our study, we have prepared CF, CLA, and CF + CLA loaded-solid lipid nanoparticles (SLN) since the SLNs are cost-effective, tissue-localized, and highly stable. The central composite design model was preferred to select the optimized formulation. UHPLC was used for quantification related to the CF and CLA amounts. The high-pressure homogenization (HPH) method was used while SLN formulations were prepared in the presence of poloxamer® 407 (surfactant) and Compritol® 888 ATO (solid lipid). The nanoparticles were characterized, followed by the utilization of 3T3-F442A cell lines for the evaluation of the adipogenesis activity of the formulations. Then, rt-PCR and ELISA studies of adipogenic markers were conducted. After optimal formulations were selected with an average of 110.2 ± 0.1 nm, CF (1 mM) + CLA (0.5 mM)-loaded SLN formulation has been proven significantly effective by using PPAR-γ/C/EBP-a pathways. In a nutshell, our study has shown that CF + CLA loaded-SLN has been affected 45.8% times more than regular extracted coffee (p < 0.05) on the adipocyte cells.

Visualization of the granule temperature using thermal imaging to improve understanding of the granulation mechanism in continuous twin-screw melt granulation

The aim of this study is to increase process understanding of the granulation mechanism in twin-screw melt granulation by evaluating the influence of different screw configurations on granule formation and granule temperature via thermal imaging. The study used a Design of Experiments (DoE) to process a miscible and immiscible formulation (85% API/binder w/w) using a twin-screw extruder with varying screw configurations. The barrel temperature (°C), screw speed (rpm), throughput (kg/h), and kneading zone (direction and stagger angle) were varied. Granule and process properties were evaluated for samples collected at four different locations along the length of the granulation barrel to visualize the granule formation, and granule temperature was monitored by an infrared camera to measure heat transfer on the granules. The resulting temperature was linked to the granule properties and the granule formation along the length of the barrel. The most influencing factors on the granule temperature are the direction of the kneading zone and the set barrel temperature. It was observed that granule formation mainly occurred in the zones that apply more kneading on the granules. The highest temperature increase was observed when the smallest stagger angle in reverse configuration was used, and could be linked to better granule quality attributes.

Antidepressant-like Effects of Representative Types of Food and Their Possible Mechanisms

Depression is a mental disorder characterized by low mood, lack of motivation, negative cognitive outlook, and sleep problems. Suicide may occur in severe cases, although suicidal thoughts are not seen in all cases. Globally, an estimated 350 million individuals grapple with depression, as reported by the World Health Organization. At present, drug and psychological treatments are the main treatments, but they produce insufficient responses in many patients and fail to work at all in many others. Consequently, treating depression has long been an important topic in society. Given the escalating prevalence of depression, a comprehensive strategy for managing its symptoms and impacts has garnered significant attention. In this context, nutritional psychiatry emerges as a promising avenue. Extensive research has underscored the potential benefits of a well-rounded diet rich in fruits, vegetables, fish, and meat in alleviating depressive symptoms. However, the intricate mechanisms linking dietary interventions to brain function alterations remain largely unexplored. This review delves into the intricate relationship between dietary patterns and depression, while exploring the plausible mechanisms underlying the impact of dietary interventions on depression management. As we endeavor to unveil the pathways through which nutrition influences mental well-being, a holistic perspective that encompasses multidisciplinary strategies gains prominence, potentially reshaping how we approach and address depression.

Comprehensive Review of Nutraceuticals against Cognitive Decline Associated with Alzheimer's Disease

Nowadays, nutraceuticals are being incorporated into functional foods or used as supplements with nonpharmacological approaches in the prevention and management of several illnesses, including age-related conditions and chronic neurodegenerative diseases. Nutraceuticals are apt for preventing and treating such disorders because of their nontoxic, non-habit-forming, and efficient bioactivities for promoting neurological well-being due to their ability to influence cellular processes such as neurogenesis, synaptogenesis, synaptic transmission, neuro-inflammation, oxidative stress, cell death modulation, and neuronal survival. The capacity of nutraceuticals to modify all of these processes reveals the potential to develop food-based strategies to aid brain development and enhance brain function, prevent and ameliorate neurodegeneration, and possibly reverse the cognitive impairment observed in Alzheimer's disease, the most predominant form of dementia in the elderly. The current review summarizes the experimental evidence of the neuroprotective capacity of nutraceuticals against Alzheimer's disease, describing their mechanisms of action and the in vitro and in vivo models applied to evaluate their neuroprotective potential.

Discovery of blood-brain barrier permeable and orally bioavailable caffeine-based amide derivatives as acetylcholinesterase inhibitors

Caffeine is one of the privileged natural products that shows numerous effects on the central nervous system. Herein, thirty-one caffeine-based amide derivatives were synthesized and evaluated in vitro for their anticholinesterase activity. The introduction of the amide group to the caffeine core augmented its anticholinesterase activity from an IC50 value of 128 to 1.32 µM (derivative, 6i). The SAR study revealed that N7 substitution on caffeine core is favorable over N1, and the presence of amide 'carbonyl' as a part of the linker contributes to the biological activity. The caffeine core of 6i exhibits interactions with the peripheral anionic site, whereas the N-benzyl ring fits nicely inside the catalytic anionic site. Analog 6i inhibits AChE in a mixed-type mode (Ki 4.58 µM) and crosses the BBB in an in-vitro PAMPA assay. Compound 6i has a descent metabolic stability in MLM (>70% remaining after 30 min) and favorable oral pharmacokinetics in Swiss albino mice.

Electrochemical Sensing Platform Based on Carbon Dots for the Simultaneous Determination of Theophylline and Caffeine in Tea

A simple and selective method for the determination of caffeine (CAF) and theophylline (THEO) has been developed for a glassy carbon electrode (GCE) modified with a composite including carbon dots (CDs) and chitosan (CS). To our knowledge, there are no previous studies that analyze a CDs-modified GCE for the presence of CAF and THEO. The electrochemical behavior of a GCE modified with a CDs-CS composite was studied in acidic medium by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Considering the sensor analytical parameters, the same linear concentrations range was found for CAF and THEO ranging from 1 × 10-5 to 5 × 10-3 mol L-1 with the same detection limit (LOD) of 1 × 10-6 mol L-1. The reproducibility and repeatability data were satisfactory in terms of RSD%. Moreover, the storage stability was evaluated, evidencing good results whatever the experimental conditions used. The developed sensor was applied for the simultaneous determination of CAF and THEO in tea and drug, and results were compared with those obtained with HPLC-ESI-MS in SIR mode as an independent method optimized on purpose. The electrochemical sensor presents the undoubled advantages in terms of cheapness, portability, and ease of use, since it does not require skilled personnel.

Metal complexes of xanthine and its derivatives: Synthesis and biological activity

Xanthine and its derivatives are considered an important class of N-heterocyclic purine compounds that have gained significant importance in medicinal chemistry. N-heterocyclic carbene (NHC) and N-coordinated metal complexes of xanthine and its derivatives have revealed a range of new possibilities for their use as therapeutic agents in addition to their established catalytic behavior. The metal complexes of xanthine and its derivatives have been designed and synthesized for the exploration of their potential therapeutic applications. These metal complexes based on the xanthine scaffold exhibited various potential medicinal applications including anticancer, antibacterial, and antileishmanial activity. The metal complexes of xanthine and its derivatives shall pave the way for the rational design and development of new therapeutic agents. In the present comprehensive review, we highlighted the recent advancements in the synthesis and medicinal applications of metal complexes based on N-heterocyclic carbene (NHC) derived from xanthine scaffolds.

The Effect of Caffeine on Heart Rate Variability in Newborns: A Pilot Study

Neonatal apnoea can be treated with caffeine, which affects the central nervous and cardiovascular systems. Heart rate variability (HRV) reflects the activity of the autonomic nervous system (ANS) and might be used as a measure of ANS maturation in newborns. We aimed to establish the effect of caffeine on HRV in newborns and investigated the potential correlation between HRV and postmenstrual age (PMA). In 25 haemodynamically stable newborns hospitalized due to apnoea and treated with caffeine (2.5 mg/kg), we assessed breathing frequency, arterial oxygen saturation, body temperature, and the heart rate while they were sleeping. We assessed HRV by spectral analysis using fast Fourier transformation. The same protocol was reapplied 100 h after caffeine withdrawal to assess the control parameters. Caffeine increased breathing frequency (p = 0.023) but did not affect any other parameter assessed including HRV. We established a positive correlation between postmenstrual age and HRV during treatment with caffeine as well as after caffeine had been withdrawn (total power: p = 0.044; low-frequency band: p = 0.039). Apparently, the maintenance dose of caffeine is too low to affect the heart rate and HRV. A positive correlation between PMA and HRV might reflect maturation of the ANS, irrespective of caffeine treatment.

A Determination of the Caffeine Content in Dietary Supplements According to Green Chemistry Principles

Caffeine is a natural psychoactive substance that belongs to a group of chemical compounds called purine alkaloids. Caffeine is found in various plants such as coffee, tea, cocoa, guarana, and yerba mate. It is often added to dietary supplements for its ability to increase metabolism and aid in weight loss. To determine the caffeine content in dietary supplements, a novel UHPLC method was developed, compatible with the rules of green analytical chemistry. The developed method used only water and ethanol for sample preparation and chromatographic separation on a short C18 column. The obtained method confirmed that caffeine may be analyzed using only environmentally friendly solvents, ethanol, and water. The developed method is characterized by its low limit of quantitation, equal to 0.047 µg/mL, and good reproducibility (a relative standard deviation lower than 1.1%). The obtained results show that the caffeine content in tested dietary supplements is 4-35% higher than the declared amount in most cases. In comparison, the caffeine content of the drug determined using this method was performed with an accuracy of 0.4% RSD.

Synergistic Effects of Caffeine in Combination with Conventional Drugs: Perspectives of a Drug That Never Ages

Plants have been known since ancient times for their healing properties, being used as preparations against human diseases of different etiologies. More recently, natural products have been studied and characterized, isolating the phytochemicals responsible for their bioactivity. Most certainly, there are currently numerous active compounds extracted from plants and used as drugs, dietary supplements, or sources of bioactive molecules that are useful in modern drug discovery. Furthermore, phytotherapeutics can modulate the clinical effects of co-administered conventional drugs. In the last few decades, the interest has increased even more in studying the positive synergistic effects between plant-derived bioactives and conventional drugs. Indeed, synergism is a process where multiple compounds act together to exert a merged effect that is greater than that of each of them summed together. The synergistic effects between phytotherapeutics and conventional drugs have been described in different therapeutic areas, and many drugs are based on synergistic interactions with plant derivatives. Among them, caffeine has shown positive synergistic effects with different conventional drugs. Indeed, in addition to their multiple pharmacological activities, a growing body of evidence highlights the synergistic effects of caffeine with different conventional drugs in various therapeutic fields. This review aims to provide an overview of the synergistic therapeutic effects of caffeine and conventional drugs, summarizing the progress reported to date.

Oolong tea of different years protects high-fat diet-fed mice against obesity by regulating lipid metabolism and modulating the gut microbiota

Long-term stored oolong tea has recently attracted considerable attention concerning its salutary effect. In this study, the anti-obesity effect of different years' oolong tea on high-fat diet-fed mice was compared. Wuyi rock tea of 2001, 2011, and 2020 were chosen to be the representative samples of oolong tea. The results showed that eight-week administration of 2001 Wuyi rock tea (WRT01), 2011 Wuyi rock tea (WRT11), and 2020 Wuyi rock tea (WRT20) extracts (400 mg per kg per d) significantly decreased the body weight and attenuated the obesity in high-fat diet-fed mice. 2001 and 2011 Wuyi rock teas reduced obesity mainly through regulating lipid metabolism and activating the AMPK/SREBP-1 pathway, downregulating the expression of SREBP-1, FAS, and ACC and upregulating CPT-1a expression; while the 2011 and 2020 Wuyi rock teas by moderating the gut microbiota dysbiosis, reshaping the gut microbiota, and promoting the growth of beneficial bacteria, especially Akkermansia. 2011 Wuyi rock tea was proven to be more effective in reducing body weight gain and liver oxidative stress than the others. Collectively, all three Wuyi rock teas of different years alleviated high-fat diet-induced obesity by regulating lipid metabolism and modulating gut microbiota, whereas the emphasis of their internal mechanism is different with different storage ages.

The TMEM16A blockers benzbromarone and MONNA cause intracellular Ca2+-release in mouse bronchial smooth muscle cells

We investigated effects of TMEM16A blockers benzbromarone, MONNA, CaCC_inhA01 and Ani9 on isometric contractions in mouse bronchial rings and on intracellular calcium in isolated bronchial myocytes. Separate concentrations of carbachol (0.1-10 μM) were applied for 10 min periods to bronchial rings, producing concentration-dependent contractions that were well maintained throughout each application period. Benzbromarone (1 μM) markedly reduced the contractions with a more pronounced effect on their sustained component (at 10 min) compared to their initial component (at 2 min). Iberiotoxin (0.3 μM) enhanced the contractions, but they were still blocked by benzbromarone. MONNA (3 μM) and CaCC_inhA01 (10 μM) had similar effects to benzbromarone, but were less potent. In contrast, Ani9 (10 μM) had no effect on carbachol-induced contractions. Confocal imaging revealed that benzbromarone (0.3 μM), MONNA (1 μM) and CaCC_inhA01 (10 μM) increased intracellular calcium in isolated myocytes loaded with Fluo-4AM. In contrast, Ani9 (10 μM) had no effect on intracellular calcium. Benzbromarone and MONNA also increased calcium in calcium-free extracellular solution, but failed to do so when intracellular stores were discharged with caffeine (10 mM). Caffeine was unable to cause further discharge of the store when applied in the presence of benzbromarone. Ryanodine (100 μM) blocked the ability of benzbromarone (0.3 μM) to increase calcium, while tetracaine (100 μM) reversibly reduced the rise in calcium induced by benzbromarone. We conclude that benzbromarone and MONNA caused intracellular calcium release, probably by opening ryanodine receptors. Their ability to block carbachol contractions was likely due to this off-target effect.

Novel Therapeutic Targets for Migraine

Migraine, a primary headache disorder involving a dysfunctional trigeminal vascular system, remains a major debilitating neurological condition impacting many patients' quality of life. Despite the success of multiple new migraine therapies, not all patients achieve significant clinical benefits. The success of CGRP pathway-targeted therapy highlights the importance of translating the mechanistic understanding toward effective therapy. Ongoing research has identified multiple potential mechanisms in migraine signaling and nociception. In this narrative review, we discuss several potential emerging therapeutic targets, including pituitary adenylate cyclase-activating polypeptide (PACAP), adenosine, δ-opioid receptor (DOR), potassium channels, transient receptor potential ion channels (TRP), and acid-sensing ion channels (ASIC). A better understanding of these mechanisms facilitates the discovery of novel therapeutic targets and provides more treatment options for improved clinical care.

Protective Effects of Early Caffeine Administration in Hyperoxia-Induced Neurotoxicity in the Juvenile Rat

High-risk preterm infants are affected by a higher incidence of cognitive developmental deficits due to the unavoidable risk factor of oxygen toxicity. Caffeine is known to have a protective effect in preventing bronchopulmonary dysplasia associated with improved neurologic outcomes, although very early initiation of therapy is controversial. In this study, we used newborn rats in an oxygen injury model to test the hypothesis that near-birth caffeine administration modulates neuronal maturation and differentiation in the hippocampus of the developing brain. For this purpose, newborn Wistar rats were exposed to 21% or 80% oxygen on the day of birth for 3 or 5 days and treated with vehicle or caffeine (10 mg/kg/48 h). Postnatal exposure to 80% oxygen resulted in a drastic reduction of associated neuronal mediators for radial glia, mitotic/postmitotic neurons, and impaired cell-cycle regulation, predominantly persistent even after recovery to room air until postnatal day 15. Systemic caffeine administration significantly counteracted the effects of oxygen insult on neuronal maturation in the hippocampus. Interestingly, under normoxia, caffeine inhibited the transcription of neuronal mediators of maturing and mature neurons. The early administration of caffeine modulated hyperoxia-induced decreased neurogenesis in the hippocampus and showed neuroprotective properties in the neonatal rat oxygen toxicity model.

Effects of caffeine, methylliberine, and theacrine on vigilance, marksmanship, and hemodynamic responses in tactical personnel: a double-blind, randomized, placebo-controlled trial

Background

Tactical athletes require fast reaction times (RT) along with high levels of vigilance and marksmanship performance. Caffeine has been shown to improve these measures but also results in increased blood pressure and jitteriness. Research on other purine alkaloids, such as methylliberine and theacrine, has suggested they do not increase blood pressure or jitteriness to the same extent, but their impact on tactical performance is unknown.

Methods

A between-subjects, randomized, placebo-controlled design was used to test the effects of placebo (PLA), 300 mg caffeine (CAF), and a combination of 150 mg caffeine, 100 mg methylliberine, and 50 mg theacrine (CMT) on RT and marksmanship along with hemodynamic and arousal measures following a sustained vigilance task in tactical personnel (n = 48). Following consumption of the supplement, participants underwent a 150-min protocol consisting of two rounds. Each round began with leisurely reading followed by a 30-min vigilance task before beginning two trials of movement and marksmanship tasks. Hemodynamics and felt arousal were assessed throughout the protocol. Composite Z-scores were calculated for overall performance measures at each timepoint, and mixed-effects models were used to assess differences in RT, accuracy, and composite Z-scores along with hemodynamics and felt arousal. An α-level of 0.05 was used to determine statistical significance, and Cohen’s d was used to quantify effect sizes.

Results

A Group-by-Time interaction for vigilance RT (P = 0.038) indicated improvements for both CAF and CMT from round 1 to round 2 (P < 0.01) while PLA did not change (P = 0.27). No Group main effects or Group-by-Time interactions were found for movement or marksmanship performance (P > 0.20). Group main effects for systolic (SBP; P = 0.001) and diastolic blood pressure (DBP; P = 0.028) indicated higher SBP in CAF (P = 0.003, d= 0.84) and CMT (P = 0.007, d= 0.79) compared to PLA but only higher DBP in CAF (P = 0.025, d= 0.74). No Group-by-Time interaction or Group main effect was found for felt arousal (P > 0.16).

Conclusions

These findings suggest similar benefits on RT during a vigilance task between CAF, containing 300 mg caffeine, and CMT above PLA, though CAF resulted in slightly less favorable hemodynamic changes. This study is the first to provide data showing similar efficacy of combined caffeine, methylliberine, and theacrine compared to double the caffeine dose consumed alone on vigilance RT but without a significant rise in DBP above PLA in tactical personnel.

Design, Synthesis and Assay of Novel Methylxanthine-Alkynylmethylamine Derivatives as Acetylcholinesterase Inhibitors

Xanthine derivatives have been a great area of interest for the development of potent bioactive agents. Thirty-eight methylxanthine derivatives as acetylcholinesterase inhibitors (AChE) were designed and synthesized. Suzuki-Miyaura cross-coupling reactions of 8-chlorocaffeine with aryl(hetaryl)boronic acids, the CuAAC reaction of 8-ethynylcaffeine with several azides, and the copper(I) catalyzed one-pot three-component reaction (A³-coupling) of 8-ethynylcaffeine, 1-(prop-2-ynyl)-, or 7-(prop-2-ynyl)-dimethylxanthines with formaldehyde and secondary amines were the main approaches for the synthesis of substituted methylxanthine derivatives (yield 53-96%). The bioactivity of all new compounds was evaluated by Ellman's method, and the results showed that most of the synthesized compounds displayed good and moderate acetylcholinesterase (AChE) inhibitory activities in vitro. The structure-activity relationships were also discussed. The data revealed that compounds 53, 59, 65, 66, and 69 exhibited the most potent inhibitory activity against AChE with IC₅₀ of 0.25, 0.552, 0.089, 0.746, and 0.121 μM, respectively. The binding conformation and simultaneous interaction modes were further clarified by molecular docking studies.

Elevation of Anticancer Drug Toxicity by Caffeine in Spheroid Model of Human Lung Adenocarcinoma A549 Cells Mediated by Reduction in Claudin-2 and Nrf2 Expression

Claudin-2 (CLDN2), a component of tight junctions, is abnormally expressed in human lung adenocarcinoma tissue. CLDN2 contributes to chemoresistance in human lung adenocarcinoma-derived A549 cells, and it may be a target for cancer therapy. Here, we found that coffee ingredients, namely caffeine and theobromine, decreased the protein level of CLDN2 in human lung adenocarcinoma-derived A549 cells. In contrast, other components, such as theophylline and chlorogenic acid, had no effect. These results indicate that the 7-methyl group in methylxanthines may play a key role in the reduction in CLDN2 expression. The caffeine-induced reduction in the CLDN2 protein was inhibited by chloroquine, a lysosome inhibitor. In a protein-stability assay using cycloheximide, CLDN2 protein levels decreased faster in caffeine-treated cells than in vehicle-treated cells. These results suggest that caffeine accelerates the lysosomal degradation of CLDN2. The accumulation and cytotoxicity of doxorubicin were dose-dependently increased, which was exaggerated by caffeine but not by theophylline in spheroids. Caffeine decreased nuclear factor-erythroid 2-related factor 2 (Nrf2) levels without affecting hypoxia-inducible factor-1α levels. Furthermore, caffeine decreased the expression of Nrf2-targeted genes. The effects of caffeine on CLDN2 expression and anticancer-drug-induced toxicity were also observed in lung adenocarcinoma RERF-LC-MS cells. We suggest that caffeine enhances doxorubicin-induced toxicity in A549 spheroids mediated by the reduction in CLDN2 and Nrf2 expression.

Neurodegenerative Diseases: Can Caffeine Be a Powerful Ally to Weaken Neuroinflammation?

In recent years, there has been considerable research showing that coffee consumption seems to be beneficial to human health, as it contains a mixture of different bioactive compounds such as chlorogenic acids, caffeic acid, alkaloids, diterpenes and polyphenols. Neurodegenerative diseases (NDs) are debilitating, and non-curable diseases associated with impaired central, peripheral and muscle nervous systems. Several studies demonstrate that neuroinflammation mediated by glial cells—such as microglia and astrocytes—is a critical factor contributing to neurodegeneration that causes the dysfunction of brain homeostasis, resulting in a progressive loss of structure, function, and number of neuronal cells. This happens over time and leads to brain damage and physical impairment. The most known chronic NDs are represented by Alzheimer’s disease (AD), Parkinson’s disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and Huntington’s disease (HD). According to epidemiological studies, regular coffee consumption is associated with a lower risk of neurodegenerative diseases. In this review, we summarize the latest research about the potential effects of caffeine in neurodegenerative disorders prevention and discuss the role of controlled caffeine delivery systems in maintaining high plasma caffeine concentrations for an extended time.

Design, synthesis, and structure-activity relationship of caffeine-based triazoles as dual AChE and BACE-1 inhibitors

Natural products have significantly contributed to drug discovery for neurodegenerative diseases. Caffeine is one of the well-known central nervous system(CNS)-active natural products. Besides its CNS stimulant properties, it is a mild inhibitor of acetylcholinesterase (AChE) and possesses memory-enhancing properties. The present work aimed to improve the AChE inhibition activity of the caffeine. The rationally designed caffeine-based triazoles were synthesized and evaluated in vitro for cholinesterase and β-site amyloid precursor protein cleaving enzyme-1 (BACE-1) inhibitory activities. The attachment of triazole to the caffeine enhances its AChE inhibition activity from half-maximal inhibitory concentration (IC₅₀ ) of 129 µM to 0.49 µM (derivative, 6l). The caffeine core interacts with the peripheral anionic site, whereas the benzyl triazole occupies the catalytic anionic site located at the bottom of the active site gorge. The structure-activity relationship revealed that the four-atom ester linker is superior to shorter linkers for connecting the caffeine core to the triazole. The 2,6-difluorobenzyl triazole-linked caffeine derivative, 6d, exhibits dual inhibition of AChE and BACE-1 with IC₅₀ values of 1.43 and 10.9 µM, respectively. The derivative 6d inhibits AChE via a mixed-type mode with an inhibition rate constant (K_i ) value of 2.35 μM, which was corroborated by docking studies. The triazole 6d has an acceptable stability profile in human liver microsomes (t_1/2  = 54 min) and was found to possess CNS permeability when evaluated using the parallel artificial membrane permeability blood-brain barrier assay. The results presented herein warrant investigating caffeine-based triazoles in preclinical models of Alzheimer's disease.

Systematic Analysis and Prediction of the Target Space of Bioactive Food Compounds: Filling the Chemobiological Gaps

Food compounds and their molecular interactions are crucial for health and provide new chemotypes and targets for drug and nutraceutic design. Here, we retrieve and analyze the complete set of published interactions of food compounds with human proteins using the FooDB as a compound set and ChEMBL as a source of interactions. The data are analyzed in terms of 19 target classes and 19 compound classes, showing a small fraction of target assignment for the compounds (1.6%) and unraveling multiple gaps in the chemobiological space for these molecules. By using well-established cheminformatic approaches [similarity ensemble approach (SEA) combined with the maximum Tanimoto coefficient to the nearest bioactive, "SEA + TC"], we achieve a much enhanced target assignment (64.2%), filling many of the gaps with target hypothesis for fast focused testing. By publishing these data sets and analyses, we expect to provide a set of resources to speed up the full clarification of the chemobiological space of food compounds, opening new opportunities for drug and nutraceutic design.

Effects of Caffeine and 5-Caffeoylquinic Acid on Blood Cell In Vitro Cytokine Production in Response to Lipopolysaccharide Stimulation

Previous in vitro studies the have suggested anti-inflammatory properties of caffeine. Coffee is also rich in phenolic acids with several potential health benefits (chlorogenic acids), mainly 5-caffeoylquinic acid (5-CQA). The aim of the present study was to determine the effect of caffeine and 5-CQA, using concentrations comparable to typical human consumption, on LPS-induced cytokine production in whole blood in vitro cultures. Whole blood samples (n = 10) were stimulated for 24 h with LPS in the presence of caffeine or 5-CQA. The concentrations of various cytokines, malondialdehyde (MDA) and adenosine-3′,5′-cyclic monophosphate (cAMP) were determined in the culture media. Significant effects of caffeine were found only for the stimulated production of TNF-α (p = 0.014) and cAMP (p = 0.001). However, only the highest caffeine concentration (50 μM) induced lower TNF-α (p = 0.016) and higher cAMP (p = 0.006) levels in comparison to the control. The 5-CQA only influenced the stimulated production of IL-6 (p = 0.002), with lower values for the highest 5-CQA concentrations (2 μM: p = 0.012; 20 μM: p < 0.001). Neither caffeine (p = 0.227) nor 5-CQA (p = 0.259) influenced MDA concentrations. In conclusion, both caffeine and 5-CQA exerted limited in vitro anti-inflammatory effects. For caffeine, these effects were attained with high physiological concentrations. However, for 5-CQA, supraphysiological concentrations were needed.

The Conflicting Role of Caffeine Supplementation on Hyperoxia-Induced Injury on the Cerebellar Granular Cell Neurogenesis of Newborn Rats

Preterm birth disrupts cerebellar development, which may be mediated by systemic oxidative stress that damages neuronal developmental stages. Impaired cerebellar neurogenesis affects several downstream targets important for cognition, emotion, and speech. In this study, we demonstrate that oxidative stress induced with high oxygen (80%) for three or five postnatal days (P3/P5) could significantly damage neurogenesis and proliferative capacity of granular cell precursor and Purkinje cells in rat pups. Reversal of cellular neuronal damage after recovery to room air (P15) was augmented by treatment with caffeine. However, downstream transcripts important for migration and differentiation of postmitotic granular cells were irreversibly reduced by hyperoxia, without rescue by caffeine. Protective effects of caffeine in the cerebellum were limited to neuronal survival but failed to restore important transcript signatures.

Effect of Nitric Oxide Synthase Inhibitor on the Learning and Spatial Memory in Rats Subjected to Long-Term Perinatal Administration of Caffeine

We studied the effect of inducible nitric oxide synthase inhibitor aminoguanidine on learning and spatial memory in rats exposed to long-term administration to caffeine during the prenatal and early postnatal periods. The rats perinatally receiving caffeine demonstrated high learning ability in the Morris water maze. At the same time, the ability to remember the location of the hidden platform in the trial probe in these rats was reduced in comparison with that of the control group rats perinatally receiving water. Administration of aminoguanidine to rats under conditions of perinatal exposure to caffeine significantly improved the parameters of spatial learning and memory. Thus, inhibition of inducible nitric oxide synthase has a beneficial effect on the cognitive functions in offspring perinatally receiving caffeine.

A Green High-Performance Thin-Layer Chromatography Method for the Determination of Caffeine in Commercial Energy Drinks and Formulations

The literature on green analytical approaches for caffeine estimation is limited. As a consequence, this study aimed to establish a reverse-phase high-performance thin-layer chromatography (HPTLC) technique for caffeine estimation in a variety of commercial energy drinks (ED) and pharmaceutical formulations that is rapid, sensitive, and green. The combination of ethanol-water (55:45 v v−1) was used as a mobile phase. The detection of caffeine was carried out at 275 nm. The green reverse-phase HPTLC method was linear in the concentration range of 50−800 ng band−1. Furthermore, the developed method for caffeine estimation was simple, quick, economical, accurate, precise, robust, sensitive, and green. The amount of caffeine in different marketed ED (ED1−ED10) was recorded in the range of 21.02−37.52 mg 100 mL−1 using the developed HPTLC method. However, the amount of caffeine in different commercial formulations (F1−F3) was estimated as 10.63−20.30 mg 100 mL−1 using the same method. The “analytical GREEnness (AGREE)” scale for the developed analytical method was predicted to be 0.80, utilizing 12 distinct components of green analytical chemistry, indicating the HPTLC approach’s excellent greener profile. Overall, the developed method for estimating caffeine in marketed ED and dosage forms was found to be reliable.

Involvement of adenosine signaling pathway in migraine pathophysiology: a systematic review of preclinical studies

Background

Adenosine is a purinergic signaling molecule with a wide range of physiological functions including anti- and pronociceptive properties. Adenosine receptors are expressed in the trigeminovascular system, and adenosine receptor antagonist, caffeine, relieves migraine headache. We performed a systematic review of the literature of preclinical data addressing the role of adenosine in migraine pathophysiology.

Methods

PubMed and EMBASE were searched for pre-clinical studies on the role of adenosine in migraine pathophysiology on September 5^th, 2021.

Results

A total of 2510 studies were screened by title and abstract. Of these, thirteen pre-clinical studies evaluating adenosine, adenosine A1, A2A and A3 receptors were included.

These studies showed that adenosine signaling pathway is involved in controlling vascular tone. Furthermore, electrical stimulation of the trigeminal ganglion modulates the expression of adenosine A₁ and A_2A receptors in the trigeminal ganglion and trigeminal nucleus caudalis implicating adenosine signaling pathway in pain transmission.

Conclusion

Preclinical studies showed that adenosine has a dual effect on vasodilation and trigeminal pain pathway due to different receptor activation, suggesting a possible role of adenosine in migraine pathophysiology. Studies investigating pharmacological characteristics of subtypes of adenosine receptors are needed to further elucidate their role as a potential target for migraine treatment.

Involvement of adenosine signaling pathway in migraine pathophysiology: A systematic review of clinical studies

OBJECTIVE

To systematically review clinical studies investigating the involvement of adenosine and its receptors in migraine pathophysiology.

BACKGROUND

Adenosine is a purinergic signaling molecule, clinically used in cardiac imaging during stress tests. Headache is a frequent adverse event after intravenous adenosine administration. Migraine headache relief is reported after intake of adenosine receptor antagonist, caffeine. These findings suggest a possible involvement of adenosine signaling in migraine pathophysiology and its potential as a drug target.

METHODS

A search through PubMed and EMBASE was undertaken for clinical studies investigating the role of adenosine and its receptors in migraine, published until September 2021.

RESULTS

A total of 2510 studies were screened by title and abstract. Of these, seven clinical studies were included. The main findings were that adenosine infusion induced headache, and plasma adenosine levels were elevated during ictal compared to interictal periods in migraine patients.

CONCLUSION

The present systematic review emphasizes a potentially important role of adenosine signaling in migraine pathogenesis. Further randomized and placebo-controlled clinical investigations applying adenosine receptors modulators in migraine patients are needed to further understand the adenosine involvement in migraine.

Analysis of Conformational Preferences in Caffeine

High level DLPNO−CCSD(T) electronic structure calculations with extended basis sets over B3LYP−D3 optimized geometries indicate that the three methyl groups in caffeine overcome steric hindrance to adopt uncommon conformations, each one placing a C−H bond on the same plane of the aromatic system, leading to the C−H bonds eclipsing one carbonyl group, one heavily delocalized C−N bond constituent of the fused double ring aromatic system, and one C−H bond from the imidazole ring. Deletion of indiscriminate and selective non-Lewis orbitals unequivocally show that hyperconjugation in the form of a bidirectional −CH3 ⇆ aromatic system charge transfer is responsible for these puzzling conformations. The structural preferences in caffeine are exclusively determined by orbital interactions, ruling out electrostatics, induction, bond critical points, and density redistribution because the steric effect, the allylic effect, the Quantum Theory of Atoms in Molecules (QTAIM), and the non-covalent interactions (NCI), all predict wrong energetic orderings. Tiny rotational barriers, not exceeding 1.3 kcal/mol suggest that at room conditions, each methyl group either acts as a free rotor or adopts fluxional behavior, thus preventing accurate determination of their conformations. In this context, our results supersede current experimental ambiguity in the assignation of methyl conformation in caffeine and, more generally, in methylated xanthines and their derivatives.

A Sulfonated Tweezer-Shaped Receptor Selectively Recognizes Caffeine in Water

The selective recognition of caffeine in water among structurally related xanthines and purine or pyrimidine bases was achieved by a simple tweezer-shaped receptor featuring sulfonate hydrosolubilizing groups. The remarkable affinity for caffeine, among the highest reported thus far in the literature and larger than that shown by adenosine receptors of all subtypes, stems from a synergistic combination of hydrogen bonding, CH−π, and π-stacking interactions.

Thermodynamics of the elementary steps of organic hydride chemistry determined in acetonitrile and their applications

This review focuses on the thermodynamics of the elementary step of 421 organic hydrides and unsaturated compounds releasing or accepting hydride or hydrogen determined in acetonitrile as well as their potential applications.

Multicomponent Materials to Improve Solubility: Eutectics of Drug Aminoglutethimide

Here, we report the synthesis and experimental characterization of three drug-drug eutectic mixtures of drug aminoglutethimide (AMG) with caffeine (CAF), nicotinamide (NIC) and ethenzamide (ZMD). The eutectic mixtures i.e., AMG-CAF (1:0.4, molar ratio), AMG-NIC (1:1.9, molar ratio) and AMG-ZMD (1:1.4, molar ratio) demonstrate significant melting point depressions ranging from 99.2 to 127.2 °C compared to the melting point of the drug AMG (151 °C) and also show moderately higher aqueous solubilities than that of the AMG. The results presented include the determination of the binary melt phase diagrams and accompanying analytical characterization via X-ray powder diffraction, FT-IR spectroscopy and scanning electron microscopy.

Updated Prediction of Aggregators and Assay-Interfering Substructures in Food Compounds

Positive outcomes in biochemical and biological assays of food compounds may appear due to the well-described capacity of some compounds to form colloidal aggregates that adsorb proteins, resulting in their denaturation and loss of function. This phenomenon can lead to wrongly ascribing mechanisms of biological action for these compounds (false positives) as the effect is nonspecific and promiscuous. Similar false positives can show up due to chemical (photo)reactivity, redox cycling, metal chelation, interferences with the assay technology, membrane disruption, etc., which are more frequently observed when the tested molecule has some definite interfering substructures. Although discarding false positives can be achieved experimentally, it would be very useful to have in advance a prognostic value for possible aggregation and/or interference based only in the chemical structure of the compound tested in order to be aware of possible issues, help in prioritization of compounds to test, design of appropriate assays, etc. Previously, we applied cheminformatic tools derived from the drug discovery field to identify putative aggregators and interfering substructures in a database of food compounds, the FooDB, comprising 26,457 molecules at that time. Here, we provide an updated account of that analysis based on a current, much-expanded version of the FooDB, comprising a total of 70,855 compounds. In addition, we also apply a novel machine learning model (SCAM Detective) to predict aggregators with 46-53% increased accuracies over previous models. In this way, we expect to provide the researchers in the mode of action of food compounds with a much improved, robust, and widened set of putative aggregators and interfering substructures of food compounds.

The Transcriptional Repressor Orphan Nuclear Receptor TLX Is Responsive to Xanthines

The orphan nuclear receptor tailless homologue (TLX) is expressed almost exclusively in neural stem cells acting as an essential factor for their survival and is hence considered as a promising drug target in neurodegeneration. However, few studies have characterized the roles of TLX due to the lack of ligands and limited functional understanding. Here, we identify xanthines including caffeine and istradefylline as TLX modulators that counteract the receptor's intrinsic repressor activity. Mutagenesis of residues lining a cavity within the TLX ligand binding domain altered the activity of these ligands, suggesting direct interactions with helix 5. Using xanthines as tool compounds, we observed a ligand-sensitive recruitment of the co-repressor silencing mediator for retinoid or thyroid-hormone receptors, TLX homodimerization, and heterodimerization with the retinoid X receptor. These protein-protein interactions evolve as factors that modulate the TLX function and suggest an unprecedented role of TLX in directly repressing other nuclear receptors.

Innovation in the discovery of the HIV-1 attachment inhibitor temsavir and its phosphonooxymethyl prodrug fostemsavir

The discovery and development of fostemsavir (2), the tromethamine salt of the phosphonooxymethyl prodrug of temsavir (1), encountered significant challenges at many points in the preclinical and clinical development program that, in many cases, stimulated the implementation of innovative solutions in order to enable further progression. In the preclinical program, a range of novel chemistry methodologies were developed during the course of the discovery effort that enabled a thorough examination and definition of the HIV-1 attachment inhibitor (AI) pharmacophore. These discoveries helped to address the challenges associated with realizing a molecule with all of the properties necessary to successfully advance through development and this aspect of the program is the major focus of this retrospective. Although challenges and innovation are not unusual in drug discovery and development programs, the HIV-1 AI program is noteworthy not only because of the serial nature of the challenges encountered along the development path, but also because it resulted in a compound that remains the first and only example of a mechanistically novel class of HIV-1 inhibitor that is proving to be very beneficial for controlling virus levels in highly treatment-experienced HIV-1 infected patients.

The Adenosine Pathway and Human Immunodeficiency Virus-Associated Inflammation

Human immunodeficiency virus (HIV) is associated with an increased risk of age-associated comorbidities and mortality compared to people without HIV. This has been attributed to HIV-associated chronic inflammation and immune activation despite viral suppression. The adenosine pathway is an established mechanism by which the body regulates persistent inflammation to limit tissue damage associated with inflammatory conditions. However, HIV infection is associated with derangements in the adenosine pathway that limits its ability to control HIV-associated inflammation. This article reviews the function of purinergic signaling and the role of the adenosine signaling pathway in HIV-associated chronic inflammation. This review also discusses the beneficial and potential detrimental effects of pharmacotherapeutic strategies targeting this pathway among people with HIV.