Urinary volatile compounds as biomarkers for lung cancer

Lung cancer is a leading cause of deaths in cancer. Hence, developing early-stage diagnostic tests that are non-invasive, highly sensitive, and specific is crucial. In this study, we investigated to determine whether biomarkers derived from urinary volatile organic compounds (VOCs) can be used to discriminate between lung cancer patients and normal control patients. The VOCs were extracted from the headspace by solid-phase microextraction and were analyzed by gas chromatography time-of-flight mass spectrometry. Nine putative volatile biomarkers were identified as elevated in the lung cancer group. Receiver operating characteristic curve analysis was also performed, and the markers were found to be highly sensitive and specific. Next we used principal component analysis (PCA) modeling to make comparisons compare within the lung cancer group, and found that 2-pentanone may have utility in differentiating between adenocarcinoma and squamous cell carcinomas.     

Identification of loci affecting flavour volatile emissions in tomato fruits

Fresh tomato fruit flavour is the sum of the interaction between sugars, acids, and a set of approximately 30 volatile compounds synthesized from a diverse set of precursors, including amino acids, lipids, and carotenoids. Some of these volatiles impart desirable qualities while others are negatively perceived. As a first step to identify the genes responsible for the synthesis of flavour-related chemicals, an attempt was made to identify loci that influence the chemical composition of ripe fruits. A genetically diverse but well-defined Solanum pennellii IL population was used. Because S. pennellii is a small green-fruited species, this population exhibits great biochemical diversity and is a rich source of genes affecting both fruit development and chemical composition. This population was used to identify multiple loci affecting the composition of chemicals related to flavour. Twenty-five loci were identified that are significantly altered in one or more of 23 different volatiles and four were altered in citric acid content. It was further shown that emissions of carotenoid-derived volatiles were directly correlated with the fruit carotenoid content. Linked molecular markers should be useful for breeding programmes aimed at improving fruit flavour. In the longer term, the genes responsible for controlling the levels of these chemicals will be important tools for understanding the complex interactions that ultimately integrate to provide the unique flavour of a tomato.     

Interactions between tomato volatile organic compounds and aphid behaviour

Abstract

In the tritrophic system consisting of tomato, Solanum lycopersicum (L.), the aphid Macrosiphum euphorbiae (Thomas) and its natural enemy, the parasitoid Aphidius ervi (Haliday), it has been shown that the release of volatile organic compounds following aphid attack is responsible for attracting aphid parasitoids in wind tunnel experiments. The main compounds involved in these multitrophic interactions have been characterized and quantified. In this work, the possible activity of such compounds on plant direct defences against the aphid M. euphorbiae was assessed in laboratory tests. The selected compounds were applied to uninfested tomato plants, either by evaporation or contact, and performance of aphids, in terms of plant acceptance, fixing behaviour and aphid development, calculated in standard conditions. The results showed that two compounds, namely methyl salicylate and cis-hex-3-en-1-ol, alter aphid performance. These two compounds have been reported to be those eliciting the best response by A. ervi in terms of flight behavior (wind tunnel bioassay) and antennal stimulation (EAG bioassay).     

Investigation of volatile organic biomarkers derived from Plasmodium falciparum in vitro

ABSTRACT: BACKGROUND: There remains a need for techniques that improve the sensitive detection of viable Plasmodium falciparum as part of diagnosis and therapeutic monitoring in clinical studies and usual-care management of malaria infections. A non-invasive breath test based on P. falciparum-associated specific volatile organic compounds (VOCs) could fill this gap and provide insights into parasite metabolism and pathogenicity. The aim of this study was to determine whether VOCs are present in the headspace above in vitro P. falciparum cultures. METHODS: A novel, custom-designed apparatus was developed to enable efficient headspace sampling of infected and non-infected cultures. Conditions were optimized to support cultures of high parasitaemia (>20%) to improve the potential detection of parasite-specific VOCs. A number of techniques for VOC analysis were investigated including solid phase micro-extraction using two different polarity fibres, and purge and trap/thermal desorption, each coupled to gas chromatography-mass spectrometry. Each experiment and analysis method was performed at least on two occasions. VOCs were identified by comparing their mass spectra against commercial mass spectral libraries. RESULTS: No unique malarial-specific VOCs could be detected relative to those in the control red blood cell cultures. This could reflect sequestration of VOCs into cell membranes and/or culture media but solvent extractions of supernatants and cell lysates using hexane, dichloromethane and ethyl acetate also showed no obvious difference compared to control non-parasitized cultures. CONCLUSIONS: Future in vivo studies analysing the breath of patients with severe malaria who are harbouring a parasite biomass that is significantly greater than achievable in vitro may yet reveal specific clinically-useful volatile chemical biomarkers.     

Host-mediated volatile polymorphism in a parasitic plant influences its attractiveness to pollinators

Host-plants can mediate the interactions between herbivores and their mutualists and also between parasitic plants and their mutualists. The present study reveals how a hemiparasitic plant parasitizing three host species gives rise to three distinct hemiparasite-host neighborhoods which differ in terms of volatile composition and pollinator attractiveness. The study was performed in a population of the mistletoe Tristerix verticillatus infecting three different species of hosts occurring in sympatry within a small area, thus exposing all individuals studied to similar abiotic conditions and pollinator diversity; we assessed the effect of hosts on the hemiparasites’ visual and olfactory cues for pollinator attraction. During the study period, the hemiparasite individuals were flowering but the hosts were past their flowering stage. We collected volatile organic compounds from the hemiparasite and its hosts, measured floral display characteristics and monitored bird and insect visitors to inflorescences of T. verticillatus. We showed that: (1) floral patches did not differ in terms of floral display potentially involved in the attraction of pollinators, (2) hosts and hemiparasites on each host were discriminated as distinct chemical populations in terms of their volatile chemical profiles, (3) insect visitation rates differed between hemiparasites parasitizing different hosts, and (4) volatile compounds from the host and the hemiparasite influenced the visitation of hemiparasite flowers by insects. The study showed that a species regarded as “ornithophilic” by its floral morphology was actually mostly visited by insects that interacted with its sexual organs during their visits and carried its pollen, and that host-specific plant-volatile profiles within the T. verticillatus population were associated with differential attractiveness to pollinating insects.     

Exhaled breath and fecal volatile organic biomarkers of chronic kidney disease

BackgroundWhile much is known about the effect of chronic kidney disease (CKD) on composition of body fluids little is known regarding its impact on the gases found in exhaled breath or produced by intestinal microbiome. We have recently shown significant changes in the composition of intestinal microbiome in humans and animals with CKD. This study tested the hypothesis that uremia-induced changes in cellular metabolism and intestinal microbiome may modify the volatile organic metabolites found in the exhaled breath or generated by intestinal flora.MethodsSD rats were randomized to CKD (5/6 nephrectomy) or control (sham operation) groups. Exhaled breath was collected by enclosing each animal in a glass chamber flushed with clean air, then sealed for 45 min and the trapped air collected. Feces were collected, dissolved in pure water, incubated at 37 °C in glass reactors for 24 h and the trapped air collected. Collected gases were analyzed by gas chromatography.ResultsOver 50 gases were detected in the exhaled breath and 36 in cultured feces. Four gases in exhaled breath and 4 generated by cultured feces were significantly different in the two groups. The exhaled breath in CKD rats showed an early rise in isoprene and a late fall in linear aldehydes. The CKD animals' cultured feces released larger amounts of dimethyldisulfide, dimethyltrisulfide, and two thioesters.ConclusionsCKD significantly changes the composition of exhaled breath and gaseous products of intestinal flora.General significanceAnalysis of breath and bowel gases may provide useful biomarkers for detection and progression of CKD and its complications.     

Selected volatile organic compounds as biomarkers for exposure to tobacco smoke

Cutoff levels on the scales for benzene, ethylbenzene, toluene, styrene, o-xylene and m/p-xylene in blood were developed to classify smokers from non-smokers. Self-reported smoking during the last 5 d was used as the true smoking status. Receiver operating characteristics methods that minimized the difference between specificity and sensitivity were used to develop these cutoffs. Data from National Health and Nutrition Examination Survey for the cycle 2005–2006 were used for this purpose. For the total population, a cutoff of 0.038?ng/ml for benzene was able to classify smokers from non-smokers with a sensitivity of 83.6% and specificity of 83.7%.     

Production of volatile organic compounds by mycobacteria

The need for improved rapid diagnostic tests for tuberculosis disease has prompted interest in the volatile organic compounds (VOCs) emitted by Mycobacterium tuberculosis complex bacteria. We have investigated VOCs emitted by Mycobacterium bovis BCG grown on Lowenstein-Jensen media using selected ion flow tube mass spectrometry and thermal desorption-gas chromatography-mass spectrometry. Compounds observed included dimethyl sulphide, 3-methyl-1-butanol, 2-methyl-1-propanol, butanone, 2-methyl-1-butanol, methyl 2-methylbutanoate, 2-phenylethanol and hydrogen sulphide. Changes in levels of acetaldehyde, methanol and ammonia were also observed. The compounds identified are not unique to M.?bovis BCG, and further studies are needed to validate their diagnostic value. Investigations using an ultra-rapid gas chromatograph with a surface acoustic wave sensor (zNose) demonstrated the presence of 2-phenylethanol (PEA) in the headspace of cultures of M.?bovis BCG and Mycobacterium smegmatis, when grown on Lowenstein-Jensen supplemented with glycerol. PEA is a reversible inhibitor of DNA synthesis. It is used during selective isolation of gram-positive bacteria and may also be used to inhibit mycobacterial growth. PEA production was observed to be dependent on growth of mycobacteria. Further study is required to elucidate the metabolic pathways involved and assess whether this compound is produced during in vivo growth of mycobacteria.     

Production of reactive oxygen species and induction of signaling pathways for the ACO gene expressions in tomato plants triggered by the volatile organic compound ether

Diethyl ether (ether), a volatile organic compound, is widely used as an industrial solvent and easily released to the environment. Acute exposure of tomato plants to high concentrations of ether caused young leaves to curl. Histochemical analyses revealed that superoxide anion (^•O₂ ⁻) and hydrogen peroxide were formed sequentially by ether, and that ^•O₂ ⁻ was the major ROS produced in response to ether exposure. We observed cell death by microscopic inspection of Evans blue-stained samples, following fumigation with ether for 6 h. The ethylene biosynthetic gene, 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), was induced as early as 15–30 min after ether fumigation and could be activated at ether concentration as low as 1 μL/L. Induction of ACO gene expression occurred simultaneously with ROS accumulation and coincided with the occurrence of cell death. Simultaneous treatment of tomato plants with mechanical wounding and ether induced differential expression of the ACO gene family. Ether strongly induced ACO4 and moderately induced ACO1, whereas mechanical wounding strongly induced ACO1 and slightly induced ACO4. Induction of the ACO gene family by ether occurred via different signaling pathways. While the ACO1 gene was induced via protein phosphorylation, the ACO4 gene was induced through protein dephosphorylation. Induction of ACO1 and ACO4 might be through MPK1, MPK2, MPK3, and PP2Ac1. These results suggest that the cellular responses of tomato plants to ether are different from the plant responses to ozone, and that tomato plants respond to different air pollutants through different perceptions and downstream signaling pathways.     

Production of volatile phenols by Lactobacillus plantarum in wine conditions

Some lactic acid bacteria produce volatile phenols in culture medium but this activity has not been extensively studied in wine conditions. Red and white wines were mixed with MRS medium at different ratios to study the influence of wine on the metabolism of p-coumaric and ferulic acids by Lactobacillus plantarum. In MRS broth supplemented with these precursors at 10 mg l^?1, only 4-ethylphenol was produced (1 mg l^?1) while, in the presence of wine, 4-vinylphenol was also obtained. Both volatile phenols are produced in nearly equal amounts (1 mg l^?1) or almost only 4-vinylphenol depending on the MRS:wine ratio. Thus, wine favours the accumulation of 4-vinylphenol. Ferulic acid was not or was weakly metabolized in the conditions studied.     

Cropping system influences Tomato spotted wilt virus disease development,thrips population and yield of tomato (Lycopersicon esculentum)

Yield of tomato is limited by many diseases including Tomato spotted wilt virus disease. This study was conducted in the field at Kenya Agriculture Research Institute Njoro, Kenya, in 2004 and 2006 to determine the effect of intercropping on disease development, thrips population and yield of tomato variety Cal J grown under four intercrop systems involving kale, onion, maize and sole tomato. The experimental design was a Randomised Complete Block Design (RCBD) replicated three times. Disease scores on tomato–maize differed significantly from tomato–kale and tomato–onion in both years of the study. Maize cropping system had a low significant thrips population from the other cropping systems. Tomato–maize intercrop produced the lowest fruit weights and marketable yield in 2004 and 2006, while yield of onion, kale and maize in intercrops were not significantly different from their monocrops. Land equivalent ratio was >1 in all the cropping systems.     

Production and biological function of volatile esters in Saccharomyces cerevisiae

The need to understand and control ester synthesis is driven by the fact that esters play a key role in the sensorial quality of fermented alcoholic beverages like beer, wine and sake. As esters are synthesized in yeast via several complex metabolic pathways, there is a need to gain a clear understanding of ester metabolism and its regulation. The individual genes involved, their functions and regulatory mechanisms have to be identified. In alcoholic beverages, there are two important groups of esters: the acetate esters and the medium-chain fatty acid (MCFA) ethyl esters. For acetate ester synthesis, the genes involved have already been cloned and characterized. Also the biochemical pathways and the regulation of acetate ester synthesis are well defined. With respect to the molecular basis of MCFA ethyl ester synthesis, however, significant progress has only recently been made. Next to the characterization of the biochemical pathways and regulation of ester synthesis, a new and more important question arises: what is the advantage for yeast to produce these esters? Several hypotheses have been proposed in the past, but none was satisfactorily. This paper reviews the current hypotheses of ester synthesis in yeast in relation to the complex regulation of the alcohol acetyl transferases and the different factors that allow ester formation to be controlled during fermentation.     

Postharvest temperature influences volatile lactone production via regulation of acyl-CoA oxidases in peach fruit

The biosynthesis of volatile compounds in plants is affected by environmental conditions. Lactones are considered to be peach‐like aroma volatiles; however, no enzymes or genes associated with their biosynthesis have been characterized. White‐fleshed (cv. Hujingmilu) and yellow‐fleshed (cv. Jinxiu) melting peach (Prunus persica L. Batsch) fruit were used as materials in two successive seasons and responses measured to four different temperature treatments. Five major lactones accumulated during postharvest peach fruit ripening at 20 °C. Peach fruit at 5 °C, which induces chilling injury (CI), had the lowest lactone content during subsequent shelf life after removal, while 0 °C and a low‐temperature conditioning (LTC) treatment alleviated development of CI and maintained significantly higher lactone contents. Expression of PpACX1 and activity of acyl‐CoA oxidase (ACX) with C16‐CoA tended to increase during postharvest ripening both at 20 °C and during shelf life after removal from cold storage when no CI was developed. There was a positive correlation between ACX and lactones in peach fruit postharvest. Changes in lactone production in response to temperatures are suggested to be a consequence of altered expression of PpACX1 and long‐chain ACX activity.     

Ripening‐induced acceleration of volatile aldehyde generation following tissue disruption in tomato fruit

Hexanal and cis-3-hexenal are principal flavor volatiles in ripe tomato fruit, but whether they accumulate during ripening or are formed upon maceration of the tissue has not been clarified. This has been addressed by measuring levels of these aldehydes in green and ripe fruit with discrimination between intrinsic aldehyde content and aldehyde generation following tissue disruption. Volatile sampling of tomato fruit homogenates was accomplished by purge/trapping, followed by thermal desorption on a gas chromatograph equipped with a mass selective detector. Incubation of some samples with alcohol dehydrogenase to convert the aldehydes to their respective alcohols permitted positive identification of the isomeric form of hexenal as cis-3-hexenal. Red and green tomato fruit homogenized in buffer with saturated CaCl₂ contained low (0.1-0.8 µg g^?1 fresh weight) levels of hexanal and cis-3-hexenal; thus there is minimal endogenous volatile content in intact fruit. Volatile levels increased rapidly, up to 10-fold, following homogenization of ripe tomato fruit in the absence of CaCl₂, and more modestly in corresponding green tomato fruit homogenates. Incubation with the appropriate lipoxygenase/hydroperoxide lyase substrate (linoleic acid for hexanal, linolenic acid for cis-3-hexenal) doubled the amount of volatile compound produced. Hexanal generation was suppressed in the presence of linolenic acid, suggesting that the enzyme complex has greater affinity for this substrate. As well, levels of cis-3-hexenal, but not hexanal, tended to decline within 30 min of homogenization, possibly reflecting a specific degradative process. The results collectively indicate that the contribution of six-carbon aldehydes to tomato fruit flavor is attributable to metabolism invoked following tissue disruption rather than within the intact fruit.     

Flavour compounds in tomato fruits: identification of loci and potential pathways affecting volatile composition

The unique flavour of a tomato fruit is the sum of a complexinteraction among sugars, acids, and a large set of volatilecompounds. While it is generally acknowledged that the flavourof commercially produced tomatoes is inferior, the biochemicaland genetic complexity of the trait has made breeding for improvedflavour extremely difficult. The volatiles, in particular, presenta major challenge for flavour improvement, being generated froma diverse set of lipid, amino acid, and carotenoid precursors.Very few genes controlling their biosynthesis have been identified.New quantitative trait loci (QTLs) that affect the volatileemissions of red-ripe fruits are described here. A populationof introgression lines derived from a cross between the cultivatedtomato Solanum lycopersicum and its wild relative, S. habrochaites,was characterized over multiple seasons and locations. A totalof 30 QTLs affecting the emission of one or more volatiles weremapped. The data from this mapping project, combined with previouslycollected data on an IL population derived from a cross betweenS. lycopersicum and S. pennellii populations, were used to constructa correlational database. A metabolite tree derived from thesedata provides new insights into the pathways for the synthesisof several of these volatiles. One QTL is a novel locus affectingfruit carotenoid content on chromosome 2. Volatile emissionsfrom this and other lines indicate that the linear and cyclicapocarotenoid volatiles are probably derived from separate carotenoidpools. Key words: Apocarotenoids, flavour, metabolism, quantitative trait loci, Solanum lycopersicum Received 20 August 2008; Revised 3 October 2008 Accepted 27 October 2008