Caffeine (1, 3, 7-trimethylxanthine) in Foods: A Comprehensive Review on Consumption,Functionality, Safety,and Regulatory Matters

ABSTRACT: Caffeine ranks as one of the top most commonly consumed dietary ingredients throughout the world. It is naturally found in coffee beans, cacao beans, kola nuts, guarana berries, and tea leaves including yerba mate. The total daily intake, as well as the major source of caffeine varies globally; however, coffee and tea are the 2 most prominent sources. Soft drinks are also a common source of caffeine as well as energy drinks, a category of functional beverages. Moderate caffeine consumption is considered safe and its use as a food ingredient has been approved, within certain limits, by numerous regulatory agencies around the world. Performance benefits attributed to caffeine include physical endurance, reduction of fatigue, and enhancing mental alertness and concentration. Caffeine has also been recently linked to weight loss and consequent reduction of the overall risks for developing the metabolic syndrome. However, the caloric contribution of caffeine-sweetened beverages needs to be considered in the overall energy balance. Despite all these benefits the potential negative effects of excessive caffeine intake should also be considered, particularly in children and pregnant women.     

Identification of aminoreductones as active components in Maillard reaction mixtures inducing nuclear NF‐κB translocation in macrophages

Coffee, a highly processed food, and Maillard mixtures are able to activate nuclear factor κB translocation in macrophages via generation of hydrogen peroxide. In this study, a substructure library was prepared and used to identify Maillard products that are responsible for this effect. Three different Maillard reaction products with aminoreductone substructure (C₆‐aminoreductone, C₄‐aminoreductone, and aminohexose reductone) strongly induce nuclear factor κB translocation in macrophages. The effect was almost completely blocked by co‐incubation with catalase, indicating that cellular activation was mediated by the ability of the test compounds to generate hydrogen peroxide. The cellular effect of a Maillard mixture, which was produced under conditions favoring aminoreductone formation, could be almost completely related to the presence of C₆‐aminoreductone.     

Modification with Organometallic Compounds Improves Crossing of the Blood–Brain Barrier of [Leu5]‐Enkephalin Derivatives in an In Vitro Model System

Enkephalin peptides are thought to be suitable vectors for the passage of the blood–brain barrier (BBB). Modifications that do not alter the amino acid sequence are often used to improve the permeation through living membrane systems. As a new type of modification we introduce organometallic compounds, in particular ferrocene carboxylic acid. Derivatives of [Leu⁵]enkephalin were synthesised and labelled with organometallic compounds by using solid‐phase synthesis techniques. All new metal–peptide bioconjugates were comprehensively characterised by HPLC, NMR spectroscopy and mass spectrometry and found to be at least 95 % pure. For the first time, permeation coefficients in a BBB model for organometal–peptide derivatives were determined in this work. The uptake and localisation of fluorescein‐labelled enkephalins was monitored by fluorescence microscopy on three cancer cell lines. Octanol/H₂O partition coefficients of the compounds were measured by HPLC. The introduction of the organometallic moiety enhances the uptake into cells and the permeation coefficient of [Leu⁵]‐enkephalin. This could be due to an increase in lipophilicity caused by the organometallic label. The metal–peptide conjugates were found to be nontoxic up to mM concentrations. The low cytotoxicity encourages further experiments that could take advantage of the selectivity of enkephalin derivatives for opioid receptors.     

Cytotoxic Rhodium(III) and Iridium(III) Polypyridyl Complexes: Structure–Activity Relationships,Antileukemic Activity,and Apoptosis Induction

Whereas the cytostatic agents mer‐[RhX₃(DMSO)(pp)] (X=Cl, Br; pp=phen, dpq) are considerably more potent than their facial isomers, this order is reversed for the analogous kinetically more inert Ir^III polypyridyl complexes. The complexes induce specific apoptotic cell death in leukemia and lymphoma cells via the intrinsic mitochondrial pathway and cause negligible necrotic damage.

     

A simple, valveless microfluidic sample preparation device for extraction and amplification of DNA from nanoliter-volume samples

A glass microdevice has been constructed for the on-line integration of solid-phase extraction (SPE) of DNA and polymerase chain reaction (PCR) on a single chip. The chromatography required for SPE in the microfluidic sample preparation device (muSPD) was carried out in a silica bead/sol-gel SPE bed, where the purified DNA was eluted directly into a downstream chamber where conventional thermocycling allowed for PCR amplification of specific DNA target sequences. Through rapid, simple passivation of the PCR chamber with a silanizing reagent, reproducible DNA extraction and amplification was demonstrated from complex biological matrixes in a manner amenable to any research laboratory, using only a syringe pump and a conventional thermocycler. The muSPD allowed for SPE concentration of DNA from 600 nL of blood coupled to subsequent on-chip amplification that yielded a detectable amplicon; this simple device can be applied to a variety of routine genetic analyses without the need for sophisticated instrumentation. In addition, the applicability of these developments to nonconventional thermocycling was demonstrated through the use of noncontact, IR-mediated heating. This was exemplified with the isolation of DNA from an anthrax spore-spiked nasal swab and the subsequent on-chip amplification of target DNA sequences in a total processing time of only 25 min.     

Radiation damage to DNA-protein specific complexes: estrogen response element-estrogen receptor complex

The exposure of a DNA-protein regulatory complex to ionising radiation induces damage to both partner biomolecules and thus can affect its functioning. Our study focuses on a complex formed by the estrogen response element (ERE) DNA and the recombinant human estrogen receptor alpha (ER), which mediates the signalling of female sex hormones, estrogens. The method of native polyacrylamide retardation gel electrophoresis is used to study the stability of the complex under irradiation by low LET radiation ((60)Co gamma rays) and the ability of the separately irradiated partners to form complexes. The relative probabilities of ERE DNA strand breakage and base damages as well as the probabilities of damages to the ER binding domain are calculated using the Monte Carlo method-based model RADACK.     

Processing and analytical characterisation of pulp-enriched cloudy apple juices

Pulp-enriched cloudy apple juices were manufactured from two apple varieties by blending of apple puree with natural cloudy apple juice in order to enrich bioactive secondary plant substances. Finishing of the puree with a 0.6-mm mesh screen and final product homogenisation revealed as the optimum processing technology for the novel 100% fruit beverage. The presence of large particles originating from the puree prevented long-term cloud stability, but due to the proportion of cloud-stable juice a complete phase separation did not occur. Optimal drinkability was achieved at a viscosity of 11.5 mPa s. Polyphenol compositions and concentrations were determined by means of RP-HPLC/PDA. The results ranged from 109 to 610 mg/l. All samples showed the typical polyphenol pattern of apples with dominating hydroxycinnamic acids followed by flavanols and flavonols. The puree addition to the cloudy apple juices increased the polyphenol concentrations by average 100%. Relatively, the highest increase could be observed for dimeric procyanidins. Different technological variants did not affect significantly the polyphenol concentrations. The dietary fibre contents of the pulp-enriched cloudy apple juices ranged from 5.8 to 9.4 g/l.     

Influence of different storage conditions on changes in the key aroma compounds of orange juice reconstituted from concentrate

Quantification of aroma compounds in an orange juice reconstituted from concentrate which had been stored at 37 °C for 4 weeks (forced storage) revealed an increase in the concentrations of, in particular, dimethyl sulphide, 2-methoxy-4-vinylphenol, α-terpineol, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (4-HDF) in comparison with the same orange juice before storage. On the other hand, clearly lower concentrations were found for octanal, decanal, (R)-α-pinene, linalool, and (E)-β-damascenone after storage, while the concentrations of vanillin and carvone remained nearly constant. Similar results were found for the same aroma compounds after storage of the orange juice at 20 °C for 1 year. Sensory experiments corroborated the importance of 2-methoxy-4-vinylphenol and dimethyl sulphide for the typical stale off-flavour of the stored orange juice, while the omission of e.g., α-terpineol in model mixtures could not be detected. Under both storage conditions (37 °C for 4 weeks or 20 °C for 1 year), the breakthrough odour thresholds of α-terpineol and 4-HDF were not reached, while the concentrations of dimethyl sulphide and 2-methoxy-4-vinylphenol clearly exceeded their breakthrough odour thresholds, thus confirming the crucial role of these odorants for the off-flavour of stored orange juice from concentrate. In addition, changes in the concentrations of selected orange juice odorants at various temperatures and times were investigated.     

Assessing the Role of Developmental and Environmental Factors in Chemical Defence Variation in Heliconiini Butterflies

Journal of Chemical Ecology - Chemical defences in animals are both incredibly widespread and highly diverse. Yet despite the important role they play in mediating interactions between predators...