Acetaldehyde

Alcohol consumption is a predominant etiological factor in the pathogenesis of chronic liver diseases, resulting in fatty liver, alcoholic hepatitis, fibrosis/cirrhosis, and hepatocellular carcinoma (HCC). Although the pathogenesis of alcoholic liver disease (ALD) involves complex and still unclear biological processes, the oxidative metabolites of ethanol such as acetaldehyde and reactive oxygen species (ROS) play a preeminent role in the clinical and pathological spectrum of ALD. Ethanol oxidative metabolism influences intracellular signaling pathways and deranges the transcriptional control of several genes, leading to fat accumulation, fibrogenesis and activation of innate and adaptive immunity. Acetaldehyde is known to be toxic to the liver and alters lipid homeostasis, decreasing peroxisome proliferator-activated receptors and increasing sterol regulatory element binding protein activity via an AMP-activated protein kinase (AMPK)-dependent mechanism. AMPK activation by ROS mod...

Acetaldehyde associated with alcohol consumption is a substance carcinogenic to humans (IARC group 1). Mechanistic evidence shows that acetaldehyde derived from the metabolism of ethanol contributes to causing malignant oesophageal tumours in humans being deficient in
aldehyde dehydrogenase. Acetaldehyde has a wide exposure to humans, primarily due to tobacco, alcohol and nutrition.
In foods, a considerable exposure may be due to the use as a flavouring substance, which still is ‘generally recognized as safe’. Using an average exposure of 0.2 mg/kg bodyweight/day, the lifetime cancer risk would be approximately 14 in 10000. The magnitude of risk of acetaldehyde warrants interventions based on the precautionary principle of public health. Besides general tobacco and alcohol control measures, policy should restrict the use of acetaldehyde as food flavouring additive.

Emesis, also known as nausea and vomiting, are common symptoms associated with ingestion of toxicants, drug side effects, advanced terminal diseases such as cancer and postoperative procedures. Emesis is mediated through the coordinated
action of central and peripheral regulatory centres that involve receptors including dopamine Type 2, serotonin, muscarinic cholinergic, histamine, cannabinoids and NK-1 receptors. Many anti-emetic drugs targeting these receptors are currently in
use but they also cause undesirable side effects such as excessive sedation, hypotension,dry mouth, dysphoria, hallucinations and extrapyramidal signs. This review highlights the pharmacological mechanism of emesis and current antiemtic drugs
together with detailed analysis of in vitro and in vivo anti-emetic bioassay models. The pharmacology of crude natural products extracts and purified anti-emeticcompounds (cannabinoids, chalcones, diarylheptanoids, flavonoids, hydroxycinnamic
acids, lignans, phenylpropanoids, polysaccharides, saponins, terpenes and glycosidic derivatives) are also systematically presented with their mechanism of action. The potential of natural products as sources of new clinically proven anti-emetic drugs are discussed.

Ripening, storability, quality attributes, and postharvest losses in fruits are interlinked with one another. The postharvest life of a fruit is primarily determined by various physiological processes and associated metabolic changes occurring in the fruit. The role of the external atmosphere in reg¬ulating the above processes and changes is relatively better understood. However, little is known about the overall internal atmosphere of the fruit and how it influences different aspects of ripening and storability. This chapter looks into this emerging area: the basic and applied importance of the internal atmosphere to postharvest physiology and food science and technology. There are various gases and volatiles that make the internal atmosphere of fruits. Their production and diffusion across the fruit tissues are governed by many factors. Differences in morphological, anatomical, and microstructural features of fruits are now assuming greater impor¬tance, as they are involved in determining the internal environment of fruits. As a consequence, there exists variability in the internal atmosphere of fruits, which is evident not only at the level of different species, but also within species. Differences in ripening behavior of different fruits under plant-attached and -detached conditions are also expected in view of the above. The involvement of some of gases (ethylene, oxygen, and carbon dioxide) and volatiles (ethanol, acetaldehyde, water vapors and water sta¬tus, salicylic acid and methyl salicylate, jasmonic acid and jasmonates, and nitric oxide) in the regulation of ripening-related changes, including flavor and aroma, is described and discussed at the individual as well as at the interactive level (especially with ethylene). Some examples are presented wherein endogenous and exogenous volatiles exhibit a positive effect on the fruit’s storability, quality, and tolerance to biotic and abiotic stresses. Lastly, a few researchable issues are suggested. The outcome from this area can supplement the existing storage technologies, and this will be highly desirable in achieving a more effective and holistic way of the postharvest management of perishable commodities.

Extreme weather conditions with prolonged dry periods and high temperatures as well as heavy rain events can severely influence grapevine physiology and grape quality. The present study evaluates the effects of severe drought stress on selected primary metabolites, polyphenols and volatile metabolites in grapevine leaves. Among the 11 primary metabolites, 13 polyphenols and 95 volatiles which were analyzed, a significant discrimination between control and stressed plants of 7 primary metabolites, 11 polyphenols and 46 volatile metabolites was observed. As single parameters are usually not specific enough for the discrimination of control and stressed plants, an unsupervised (PCA) and a supervised (PLS-DA) multivariate approach were applied to combine results from different metabolic groups. In a first step a selection of five metabolites, namely citric acid, glyceric acid, ribose, phenylacetaldehyde and 2-methylbutanal were used to establish a calibration model using PLS regression ...

New nanoparticle photocatalysts based on silver, carbon, and sulfur-doped TiO2 having only the homogeneous anatase crystalline phase and high surface area were successfully synthesized by a modified sol–gel route. The catalysts were characterized by EDX, XRD, BET, UV–vis, IR, and Raman spectroscopy. The effects of the experimental parameters on the visible light reactivity of the catalysts were evaluated for the photodegradation of gaseous acetaldehyde as a model indoor pollutant. The activity results show that the silver(I) ion, Ag+, doping significantly promotes the visible light reactivities of carbon and sulfur-doped TiO2 catalysts without any phase transformation from anatase to rutile. Moreover, Ag/(C, S)–TiO2 photocatalysts degrade acetaldehyde 10 times faster in visible light and 3 times faster in UV light illuminations than the accredited photocatalyst P25–TiO2. The commendable visible photoactivities of Ag/(C, S)–TiO2 new nanoparticle photocatalysts are predominantly attributable to an improvement in anatase crystallinity, high surface area, low band gap and nature of precursor materials used.New nanoparticle photocatalysts based on silver, carbon, and sulfur-doped titania (Ag/(C, S)–TiO2) degrade efficiently gaseous acetaldehyde under (a) visible and (b) UV light.

Acetaldehyde has long been suggested to be involved in a number of ethanol's pharmacological and behavioral effects, such as its reinforcing, aversive, sedative, amnesic and stimulant properties. However, the role of acetaldehyde in ethanol's effects has been an extremely controversial topic during the past two decades. Opinions ranged from those virtually denying any role for acetaldehyde in ethanol's effects to those who claimed that alcoholism is in fact "acetaldehydism". Considering the possible key role of acetaldehyde in alcohol addiction, it is critical to clarify the respective functions of acetaldehyde and ethanol molecules in the pharmacological and behavioral effects of alcohol consumption. In the present paper, we review the animal studies reporting evidence that acetaldehyde is involved in the pharmacological and behavioral effects of ethanol. A number of studies demonstrated that acetaldehyde administration induces a range of behavioral effects. O...

Strong electrophilic natured acetaldehyde present in various food and beverages damages genetic material and induces diseases like atherosclerosis. Detection and quanti fi cation of such a carcinogen poses a major challenge. In this context, a novel room temperature acetaldehyde sensor made up of hierarchical ZnO nanostructures and prepared by a simple and template-free method has been reported. ZnO nanostructures were grown on glass substrates by a chemical spray pyrolysis technique at the substrate temperature of 523 K. Di ff erent nanostructures, namely tiny nanoplatelets, branched nanorods and thicker nanoplatelets, were formed by an annealing process. The crystal structures, morphologies and optical absorbances of the hierarchical ZnO nanostructures were investigated by X-ray di ff raction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-vis spectrophotometry, respectively. The branched nanorods showed an excellent sensing response towards 20 to 500 ppm of acetaldehyde
vapour. The role of high density junctions of the branched ZnO architecture in enhancing the vapour sensing performance has been highlighted. The observed selectivity, range of detection and stability of the branched ZnO nanorods have proven their potential as a sensing element for the detection of acetaldehyde.

Aims  In addition to being produced in ethanol metabolism, acetaldehyde occurs naturally in alcoholic beverages. Limited epidemiological evidence points to acetaldehyde as an independent risk factor for cancer during alcohol consumption, in addition to the effects of ethanol. This study aims to estimate human exposure to acetaldehyde from alcoholic beverages and provide a quantitative risk assessment.Methods  The human dietary intake of acetaldehyde via alcoholic beverages was estimated based on World Health Organization (WHO) consumption data and literature on the acetaldehyde contents of different beverage groups (beer, wine, spirits and unrecorded alcohol). The risk assessment was conducted using the European Food Safety Authority's margin of exposure (MOE) approach with benchmark doses obtained from dose–response modelling of animal experiments. Life-time cancer risk was calculated using the T25 dose descriptor.Results  The average exposure to acetaldehyde from alcoholic beverages was estimated at 0.112 mg/kg body weight/day. The MOE was calculated to be 498, and the life-time cancer risk at 7.6 in 10 000. Higher risk may exist for people exposed to high acetaldehyde contaminations, as we have found in certain unrecorded alcohol beverages in Guatemala and Russia, for which we have demonstrated possible exposure scenarios, with risks in the range of 1 in 1000.Conclusions  The life-time cancer risks for acetaldehyde from alcoholic beverages greatly exceed the usual limits for cancer risks from the environment set between 1 : 10 000 and 1 : 1 000 000. Alcohol consumption has thus been identified as a direct source of acetaldehyde exposure, which in conjunction with other sources (food flavourings, tobacco) results in a magnitude of risk requiring intervention. An initial public health measure could be to reduce the acetaldehyde content in alcoholic beverages as low as technologically possible, and to restrict its use as a food flavour additive.