Article
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Like all animals, the red fox uses chemical signals for social communication. The supracaudal or tail gland smells of violets, attributed to the presence of carotenoid degradation products, or apocarotenoids, which commonly occur as aromatics in flowers. We have more fully characterized the scent chemistry of the fox tail gland. Volatile chemicals were analyzed by gas chromatography-mass spectrometry (GC-MS) and identified from their electron ionization mass spectra and Kovats retention indices. The 3 previously reported apocarotenoids were confirmed, and many additional compounds found. These include the apocarotenoids β-cyclocitral, β-homocitral, β-ionone, cyclic β-ionone, β-ionone-5,6-epoxide, α-ionene, α-ionone, 2,6,6-trimethylcyclohexanone (IUPAC 2,2,6-), 2,6,6-trimethyl-2-cyclohexen-1-one, 6-methyl-5-hepten-2-one (sulcatone), and geranyl acetone. Notably, sulcatone is a semiochemical in several species. 3,3-Dimethyl-2,7-octanedione was identified as a probable apocarotenoid which is likely to be a significant fox scent chemical. The γ-lactone of 4-hydroxyhexadecanoic acid (hexadecan-4-olide) was also found, one of a group of known mammalian signaling compounds. This rich mixture of volatile apocarotenoids implies an adequate consumption of plant carotenoids, which are known to be necessary for optimal health. Dietary carotenoids color the skin and feathers of some birds, used as a visual signal to conspecifics, and the floral aroma of the fox tail gland may provide an olfactory signal to other foxes.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... Plant carotenoids and apocarotenoids can play other ecologically relevant roles in bio-communication with plants (Section 2.4), but also between animals, such as in mimicry, aposematic colouration, camouflage, and social dominance of animals (Svensson and Wong, 2011). An example of the latter is the role of β-Cyc, β-cyclocitric acid, DHA, β-and α-ionone used by red fox as odorant molecules in chemical signalling for social communication (McLean et al., 2019). ...
... , the observed behavioural changes in the foxes were likely caused by the stimulation of the VNS, evoked by pheromones in the faeces or urine, instead of specifically induced by the smells associated with these stimuli, which are primarily composed of volatile components, with an ephemeral presence in the external environment (González et al., 1991). McLean et al. (2019 characterised the chemical compounds excreted by fox tails, identifying several compounds (for example, sulcatone) that are used as semiochemicals in several mammal species, further illustrating the importance of the VNS for fox behaviours. ...
Article
The vomeronasal system (VNS) has been extensively studied within specific animal families, such as Rodentia. However, the study of the VNS in other families, such as Canidae, has long been neglected. Among canids, the vomeronasal organ (VNO) has only been studied in detail in the dog, and no studies have examined the morphofunctional or immunohistochemical characteristics of the VNS in wild canids, which is surprising, given the well‐known importance of chemical senses for the dog and fox and the likelihood that the VNS plays roles in the socio‐reproductive physiology and behaviours of these species. In addition, characterising the fox VNS could contribute to a better understanding of the domestication process that occurred in the dog, as the fox would represent the first wild canid to be studied in depth. Therefore, the aim of this study was to analyze the morphological and immunohistochemical characteristics of the fox VNO. Tissue dissection and microdissection techniques were employed, followed by general and specific histological staining techniques, including with immunohistochemical and lectin‐histochemical labelling strategies, using antibodies against olfactory marker protein (OMP), growth‐associated protein 43 (GAP‐43), calbindin (CB), calretinin (CR), α‐tubulin, Gαo, and Gαi2 proteins, to highlight the specific features of the VNO in the fox. This study found significant differences in the VNS between the fox and the dog, particularly concerning the expression of Gαi2 and Gαo proteins, which were associated with the expression of the type 1 vomeronasal receptors (V1R) and type 2 vomeronasal receptors (V2R), respectively, in the vomeronasal epithelium. Both are immunopositive in foxes, as opposed to the dog, which only expresses Gαi2. This finding suggests that the fox possesses a well‐developed VNO and supports the hypothesis that a profound transformation in the VNS is associated with domestication in the canid family. Furthermore, the unique features identified in the fox VNO confirm the necessity of studying the VNS system in different species to better comprehend specific phylogenetic aspects of the VNS. We present the first morphofunctional study of the vomeronasal organ of a wild canid, the red fox, which highlights the importance of chemical communication in this species and opens a new perspective on the canid vomeronasal system.
Article
The increasing global population has led to rising demand for food, particularly protein. As an excellent source of protein, fish play a crucial role in meeting this demand, making aquaculture a highly impactful industry. Floating cages have been developed as a method of fish management and production to achieve high productivity and volume. However, these intensive fish farming practices can contribute to eutrophication, leading to changes in primary producers and promoting the excessive proliferation of cyanobacteria. Cyanobacteria blooms pose significant consequences to aquatic ecosystems, including potential risks to fish exposed to harmful cyanobacterial metabolites. Cyanobacterial metabolites encompass various chemical classes, such as terpenoids, carotenoids, alkaloids, cyanopeptides, amino acids, organophosphates, macrolides, and lipopolysaccharides. Some of these compounds' toxicity and impact on fish farms still need to be better understood. Cyanotoxins and off‐flavour compounds in fish farms can pose risks to water and fish quality and potential health hazards for humans throughout the food chain. Therefore, cyanobacteria in fish farms can have significant economic, environmental, and public health implications. This review examines the concerns associated with cyanobacterial natural products in fish farming, including off‐flavours, known cyanotoxins, and other potentially toxic compounds, while exploring their socioeconomic and environmental risks.
Article
Apocarotenoids are essential metabolites found in all photosynthetic and heterotrophic organisms. Apocarotenoids include phytohormones, signaling molecules, pigments, volatiles, and many other molecules used in flavor, aroma, food, and cosmetics. Apocarotenoids are a crucial component of horticulture crops’ quality and contribute to increasing their health benefits. Apocarotenoids are derived from the oxidative breakdown of carotenoids; the reaction can be enzymatic by CCDs and non-enzymatic (non-site specific) by ROS or enzymatic (site specific) by lipoxygenases and peroxidases. The enzymes belong to the family of carotenoid cleavage dioxygenase (CCDs) that includes nine different types of CCDs along with recently identified CCD10, and each plays a decisive role in catalyzing different apocarotenoids. Recent and novel apocarotenoids like β-cyclocitral, anchorene, zaxinone, and ionone were discussed. In all taxa, apocarotenoids perform crucial biological functions. They have a significant role in controlling plants’ growth, development, and reaction to biotic and abiotic environmental stimuli and mediating interactions between plants and other lifeforms. This review covers biosynthesis, isolation, characterization, and types of apocarotenoids. It also discusses the regulation of biosynthesis and CCDs genes at different levels, such as transcription (TFs, promoter, and post-transcription), post-translation, and epigenetic modifications. This review limelights the crucial role of apocarotenoids in defense against abiotic and biotic stresses. The crosstalk of apocarotenoids (SLs and ABA) with other phytohormones is also discussed.
Article
Full-text available
The red fox is a highly adaptable mammal that has established itself world-wide in many different environments. Contributing to its success is a social structure based on chemical signalling between individuals. Urine scent marking behaviour has long been known in foxes, but there has not been a recent study of the chemical composition of fox urine. We have used solid-phase microextraction and gas chromatography-mass spectrometry to analyze the urinary volatiles in 15 free-ranging wild foxes (2 female) living in farmlands and bush in Victoria, Australia. Foxes here are routinely culled as feral pests, and the urine was collected by bladder puncture soon after death. Compounds were identified from their mass spectra and Kovats retention indices. There were 53 possible endogenous scent compounds, 10 plant-derived compounds and 5 anthropogenic xenobiotics. Among the plant chemicals were several aromatic apocarotenoids previously found in greater abundance in the fox tail gland. They reflect the dietary consumption of carotenoids, essential for optimal health. One third of all the endogenous volatiles were sulfur compounds, a highly odiferous group which included thiols, methylsulfides and polysulfides. Five of the sulfur compounds (3-isopentenyl thiol, 1- and 2-phenylethyl methyl sulfide, octanethiol and benzyl methyl sulfide) have only been found in foxes, and four others (isopentyl methyl sulfide, 3-isopentenyl methyl sulfide, and 1- and 2-phenylethane thiol) only in some canid, mink and skunk species. This indicates that they are not normal mammalian metabolites and have evolved to serve a specific role. This role is for defence in musteloids and most likely for chemical communication in canids. The total production of sulfur compounds varied greatly between foxes (median 1.2, range 0.4–32.3 μg ‘acetophenone equivalents’/mg creatinine) as did the relative abundance of different chemical types. The urinary scent chemistry may represent a highly evolved system of semiochemicals for communication between foxes.
Article
β-cyclocitral is a volatile short-chain apocarotenoid generated by enzymatic or non-enzymatic oxidation of the carotenoid β-carotene. β-cyclocitral has recently emerged as a new bioactive compound in various organisms ranging from plants and cyanobacteria to fungi and animals. In vascular plants, β-cyclocitral and its direct oxidation product, β-cyclocitric acid, are stress signals that accumulate under unfavorable environmental conditions such as drought or high light. Both compounds regulate nuclear gene expression through several signaling pathways, leading to stress acclimation. In cyanobacteria, β-cyclocitral functions as an inhibitor of competing microalgae and as a repellent against grazers. As a volatile compound, this apocarotenoid plays also an important role in intra-species and inter-species communication. This review summarizes recent findings on the multiple roles of β-cyclocitral and of some of its derivatives.
Article
Full-text available
Significance The yellow, orange, and red colors of birds are produced through the deposition of carotenoid pigments into feathers and skin, and often function as signals in aggressive interactions and mate choice. These colors are hypothesized to communicate information about individual quality because their expression is linked to vital cellular processes through the mechanisms of carotenoid metabolism. To elucidate these mechanisms, we carried out genomic and biochemical analyses of the white recessive canary breed, which carries a heritable defect in carotenoid uptake. We identified a mutation in the SCARB1 gene in this breed that disrupts carotenoid transport function. Our study implicates SCARB1 as a key mediator of carotenoid-based coloration and suggests a link between carotenoid coloration and lipid metabolism.
Article
Full-text available
Carotenoid dietary intake and their endogenous levels have been associated with a decreased risk of several chronic diseases. There are indications that carotenoid bioavailability depends, in addition to the food matrix, on host factors. These include diseases (e.g. colitis), life-style habits (e.g. smoking), gender and age, as well as genetic variations including single nucleotide polymorphisms that govern carotenoid metabolism. These are expected to explain interindividual differences that contribute to carotenoid uptake, distribution, metabolism and excretion, and therefore possibly also their association with disease risk. For instance, digestion enzymes fostering micellization (PNLIP, CES), expression of uptake/efflux transporters (SRARB1, CD36, NPC1L1), cleavage enzymes (BCO1/2), intracellular transporters (FABP2), secretion into chylomicrons (APOB, MTTP), carotenoid metabolism in the blood and liver (LPL, APO C/E, LDLR), and distribution to target tissues such as adipose tissue or macula (GSTP1, StARD3) depend on the activity of these proteins. In addition, human microbiota, e.g. via altering bile-acid concentrations, may play a role in carotenoid bioavailability. In order to comprehend individual, variable responses to these compounds, an improved knowledge on intra-/interindividual factors determining carotenoid bioavailability, including tissue distribution, is required. Here, we highlight the current knowledge on factors that may explain such intra-/interindividual differences. This article is protected by copyright. All rights reserved.
Article
Full-text available
Context. Predation is one of the key contributors to mortality in freshwater turtles. Confirming the identity of predators is an important step towards conservation management action. Throughout Australia, the red fox (Vulpes vulpes) is suspected to apply significant and unsustainable predation pressure to turtle populations, killing adults and depredating nests; however methods for confirming this are limited. Aims. The present study used a range of methods to confirm predation of oblong turtle (Chelodina colliei) nests and adults by the introduced red fox. Methods. First, depredated adult carapaces, and turtle egg-shell fragments from excavated nests were swabbed and analysed for trace DNA. Second, we used artificial turtle nests, monitored by camera traps, to analyse seasonal changes in the behaviour of foxes around sites where turtle nests are present, including over the nesting season. Last, we used scat analysis to identify the prevalence of turtle remains in fox diet. Key results. Predominantly fox DNA was recovered from both adult carapaces and depredated eggs. In addition, camera traps recorded only foxes depredating artificial nests. Despite this evidence that foxes kill adults and excavated nests, we found that turtle remains were only a small part of the diet of foxes at this study site (hatchling or turtle egg shell were present in only 4% of 230 scats sampled). The diet of these foxes was largely anthropogenic-sourced foods, such as fruit (e.g. figs, grapes, melons; 81% of scats), sheep carrion (41%) and rodents (36%). Conclusions. We conclude that DNA analysis, camera trapping and scat analysis are effective methods of identifying foxes as predators of adult turtle, and their nests. Furthermore, we found that anthropogenic foods (orchard crops, livestock or synanthropic species) may subsidise greater fox population size than might occur in their absence, thereby increasing potential pressure on these freshwater turtles. Implications. Our findings give credence to the argument that foxes are effective predators of turtle adults and nests. In addition, the high proportion of anthropogenic food sources in the diet of foxes, and potential subsidisation, is an important consideration for land managers.
Article
Full-text available
β-Carotene, the precursor of vitamin A, possesses pronounced radical scavenging properties. This has centered the attention on β-carotene dietary supplementation in healthcare as well as in the therapy of degenerative disorders and several cancer types. However, two intervention trials with β-carotene have revealed adverse effects on two proband groups, that is, cigarette smokers and asbestos-exposed workers. Beside other causative reasons, the detrimental effects observed have been related to the oxidation products of β-carotene. Their generation originates in the polyene structure of β-carotene that is beneficial for radical scavenging, but is also prone to oxidation. Depending on the dominant degradation mechanism, bond cleavage might occur either randomly or at defined positions of the conjugated electron system, resulting in a diversity of cleavage products (CPs). Due to their instability and hydrophobicity, the handling of standards and real samples containing β-carotene and related CPs requires preventive measures during specimen preparation, analyte extraction, and final analysis, to avoid artificial degradation and to preserve the initial analyte portfolio. This review critically discusses different preparation strategies of standards and treatment solutions, and also addresses their protection from oxidation. Additionally, in vitro oxidation strategies for the generation of oxidative model compounds are surveyed. Extraction methods are discussed for volatile and non-volatile CPs individually. Gas chromatography (GC), (ultra)high performance liquid chromatography (U)HPLC, and capillary electrochromatography (CEC) are reviewed as analytical tools for final analyte analysis. For identity confirmation of analytes, mass spectrometry (MS) is indispensable, and the appropriate ionization principles are comprehensively discussed. The final sections cover analysis of real samples and aspects of quality assurance, namely matrix effects and method validation.
Article
Full-text available
Female mosquitoes are major vectors of human disease and the most dangerous are those that preferentially bite humans. A 'domestic' form of the mosquito Aedes aegypti has evolved to specialize in biting humans and is the main worldwide vector of dengue, yellow fever, and chikungunya viruses. The domestic form coexists with an ancestral, 'forest' form that prefers to bite non-human animals and is found along the coast of Kenya. We collected the two forms, established laboratory colonies, and document striking divergence in preference for human versus non-human animal odour. We further show that the evolution of preference for human odour in domestic mosquitoes is tightly linked to increases in the expression and ligand-sensitivity of the odorant receptor AaegOr4, which we found recognizes a compound present at high levels in human odour. Our results provide a rare example of a gene contributing to behavioural evolution and provide insight into how disease-vectoring mosquitoes came to specialize on humans.
Article
Full-text available
ABSTRACT • The successful introduction of the red fox Vulpes vulpes into Australia in the 1870s has had dramatic and deleterious impacts on both native fauna and agricultural production. Historical accounts detail how the arrival of foxes in many areas coincided with the local demise of native fauna. Recent analyses suggest that native fauna can be successfully reintroduced to their former ranges only if foxes have been controlled, and several replicated removal experiments have confirmed that foxes are the major agents of extirpation of native fauna. Predation is the primary cause of losses, but competition and transmission of disease may be important for some species. • In agricultural landscapes, fox predation on lambs can cause losses of 1–30%; variation is due to flock size, health and management, as well as differences in the timing and duration of lambing and the density of foxes. • Fox control measures include trapping, shooting, den fumigation and exclusion fencing; baiting using the toxin 1080 is the most commonly employed method. Depending on the baiting strategy, habitat and area covered, baiting can reduce fox activity by 50–97%. We review patterns of baiting in a large sheep-grazing region in central New South Wales, and propose guidelines to increase landholder awareness of baiting strategies, to concentrate and coordinate bait use, and to maximize the cost-effectiveness of baiting programs. • The variable reduction in fox density within the baited area, together with the ability of the fox to recolonize rapidly, suggest that current baiting practices in eastern Australia are often ineffective, and that reforms are required. These might include increasing landholder awareness and involvement in group control programs, and the use of more efficient broadscale techniques, such as aerial baiting.
Article
Full-text available
Gas chromatography with mass spectrometric detection (GC-MS) coupled with solid phase micro-extraction as pre-concentration method (SPME) was applied to identify and quantify volatile organic compounds (VOCs) emitted by human skin. A total of 64 C4-C10 compounds were quantified in skin emanation of 31 healthy volunteers. Amongst them aldehydes and hydrocarbons were the predominant chemical families with eighteen and seventeen species, respectively. Apart from these, there were eight ketones, six heterocyclic compounds, six terpenes, four esters, two alcohols, two volatile sulphur compounds, and one nitrile. The observed median emission rates ranged from 0.55 to 4790fmolcm(-2)min(-1). Within this set of analytes three volatiles; acetone, 6-methyl-5-hepten-2-one, and acetaldehyde exhibited especially high emission rates exceeding 100fmolcm(-2)min(-1). Thirty-three volatiles were highly present in skin emanation with incidence rates over 80%. These species can be considered as potential markers of human presence, which could be used for early location of entrapped victims during Urban Search and Rescue Operations (USaR).
Article
Full-text available
Carotenoids are natural isoprenoid pigments that provide leaves, fruits, vegetables and flowers with distinctive yellow, orange and some reddish colours as well as several aromas in plants. Their bright colours serve as attractants for pollination and seed dispersal. Carotenoids comprise a large family ofC40 polyenes and are synthesised by all photosynthetic organisms, aphids, some bacteria and fungi alike. In animals carotenoid derivatives promote health, improve sexual behaviour and are essential for reproduction. As such, carotenoids are commercially important in agriculture, food, health and the cosmetic industries. In plants, carotenoids are essential components required for photosynthesis, photoprotection and the production of carotenoid-derived phytohormones, including ABA and strigolactone. The carotenoid biosynthetic pathway has been extensively studied in a range of organisms providing an almost complete pathway for carotenogenesis. A new wave in carotenoid biology has revealed implications for epigenetic and metabolic feedback control of carotenogenesis. Developmental and environmental signals can regulate carotenoid gene expression thereby affecting carotenoid accumulation. This review highlights mechanisms controlling (1) the first committed step in phytoene biosynthesis, (2) flux through the branch to synthesis of a- and b-carotenes and (3) metabolic feedback signalling within and between the carotenoid, MEP and ABA pathways.
Article
Full-text available
Chemical communication via olfactory semiochemicals plays a central role in the social behaviour and reproduction of mammals, but even after four decades of research, only a few mammal semiochemicals have been chemically characterized. Expectations that mammal chemical signals are coded by quantitative relationships among multiple components have persisted since the earliest studies of mammal semiochemistry, and continue to direct research strategies. Nonetheless, the chemistry of mammal excretions and secretions and the characteristics of those semiochemicals that have been identified show that mammal semiochemicals are as likely to be single compounds as to be mixtures, and are as likely to be coded by the presence and absence of chemical compounds as by their quantities. There is very scant support for the view that mammal semiochemicals code signals as specific ratios between components, and no evidence that they depend on a Gestalt or a chemical image. Of 31 semiochemicals whose chemical composition is known, 15 have a single component and 16 are coded by presence/absence, one may depend on a ratio between two compounds and none of them are chemical images. The expectation that mammal chemical signals have multiple components underpins the use of multivariate statistical analyses of chromatographic data, but the ways in which multivariate statistics are commonly used to search for active mixtures leads to single messenger compounds and signals that are sent by the presence and absence of compounds being overlooked. Research on mammal semiochemicals needs to accommodate the possibility that simple qualitative differences are no less likely than complex quantitative differences to encode chemical signals.
Article
Full-text available
Vitamin A was recognized as an essential nutrient 100 years ago. In the 1930s it became clear that dietary β-carotene was cleaved at its central double to yield vitamin A (retinal or β-apo-15-carotenal). Thus a great deal of research has focused on the central cleavage of provitamin A carotenoids to form vitamin A (retinoids). The mechanisms of formation and the physiological role(s) of non-central (eccentric) cleavage of both provitamin A carotenoids and non-provitamin A carotenoids has been less clear. It is becoming apparent that the apocarotenoids exert unique biological activities themselves. These compounds are found in the diet and thus may be absorbed in the intestine, or they may form from enzymatic or non-enzymatic cleavage of the parent carotenoids. The mechanism of action of apocarotenoids in mammals is not fully worked out. However, as detailed in this review, they have profound effects on gene expression and work, at least in part, through the modulation of ligand-activated nuclear receptors. Understanding the interactions of apocarotenoids with other lipid-binding proteins, chaperones, and metabolizing enzymes will undoubtedly increase our understanding of the biological roles of these carotenoid metabolites.
Article
Full-text available
Odors emitted by human skin are of great interest to biologists in many fields; applications range from forensic studies to diagnostic tools, the design of perfumes and deodorants, and the ecology of blood-sucking insect vectors of human disease. Numerous studies have investigated the chemical composition of skin odors, and various sampling methods have been used for this purpose. The literature shows that the chemical profile of skin volatiles varies greatly among studies, and the use of different sampling procedures is probably responsible for some of these variations. To our knowledge, this is the first review focused on human skin volatile compounds. We detail the different sampling techniques, each with its own set of advantages and disadvantages, which have been used for the collection of skin odors from different parts of the human body. We present the main skin volatile compounds found in these studies, with particular emphasis on the most frequently studied body regions, axillae, hands, and feet. We propose future directions for promising experimental studies on odors from human skin, particularly in relation to the chemical ecology of blood-sucking insects.
Article
Full-text available
Gas chromatography/mass spectrometry was used to identify 103 organic compounds from urine, feces, anal glands, and preputial glands of free-ranging African wild dogs, Lycaon pictus. Aliphatic acids were the dominant class of compound in all materials. In addition to aliphatic acids, urine contained dimethyl sulfone, 1,3-propanediol, benzoic acid, 1-methyl-2,4-imidazolidinedione, and squalene as major components: feces contained indole and cholesterol; and both contained 2-piperidone, phenol, 4-methyl phenol, benzeneacetic acid, and benzenepropanoic acid and other compounds. Anal gland secretion was particularly rich in cholesterol and fatty acids, and preputial gland secretion rich in squalene. A large majority of the identified compounds have been reported from other mammals, including species sympatric with African wild dogs. Eleven of the African wild dog components have not been reported previously from mammals and have not been found in sympatric species; one component, 1-methylimidazole-5-carboxaldehyde has not been reported previously as a natural product. In the chemical profiles of their urine, feces, and anal gland secretion African wild dogs differ markedly from other canids.
Article
Full-text available
Abstract Trade-offs in resource allocation have been widely stated as the means by which the honesty of ornamental traits is maintained, but an alternative to this resource trade-off hypothesis is that production of ornamentation is linked to the biochemical efficiency of vital cellular processes. Carotenoids are antioxidants, potentially tying carotenoid-based coloration to the oxidative state of an organism, and some carotenoids are also precursors for vitamin A, which regulates numerous cellular processes. We present a biochemical model for regulation of ornamental coloration based on interdependencies of carotenoid and retinoid biochemistry. We propose that vitamin A regulatory mechanisms, redox systems, and carotenoid pigmentation pathways link carotenoid coloration to oxidative state and to a host of important aspects of performance, such as immune function. The activity of β-carotene ketolase, which catalyzes the oxidation of yellow carotenoids into red carotenoids, is responsive to the states of vitamin A pools and redox systems such that coloration is a direct reflection of the physiological state of an animal. According to the vitamin A-redox hypothesis, feather coloration is associated with a range of performance measures because performance emerges from functionality of the same basic cellular processes that regulate pigmentation. We present the vitamin A-redox hypothesis as a testable alternative hypothesis to the resource trade-off hypothesis for the maintenance of honesty of carotenoid pigmentation.
Article
Full-text available
It was long thought that the colour of bird feathers does not change after plumage moult. However, there is increasing evidence that the colour of feathers may change due to abrasion, photochemical change and staining, either accidental or deliberate. The coloration of plumage due to deliberate staining, i.e. with cosmetic purposes, may help individuals to communicate their quality to conspecifics. The presence of carotenoids in preen oils has been previously only suggested, and here we confirm for the first time its presence in such oils. Moreover, the carotenoids in the uropygial secretions were the same specific pigments found in feathers. We show not only that the colour of feathers of greater flamingos Phoenicopterus roseus became more colourful due to the application of carotenoids from uropygial secretions over the plumage but also that the feathers became more colourful with the quantity of pigments applied over them, thus providing evidence of cosmetic coloration. Flamingos used uropygial secretions as cosmetic much more frequently during periods when they were displaying in groups than during the rest of the year, suggesting that the primary function of cosmetic coloration is mate choice. Individuals with more colourful plumage initiated nesting earlier. There was a correlation between plumage coloration before and after removal of uropygial secretions from feathers’ surfaces, suggesting that the use of these pigmented secretions may function as a signal amplifier by increasing the perceptibility of plumage colour, and hence of individual quality. As the cosmetic coloration strengthens signal intensity by reinforcing base-plumage colour, its use may help to the understanding of selection for signal efficacy by making interindividual differences more apparent. KeywordsCarotenoids–Cosmetic coloration–Plumage colour–Plumage maintenance–Signals–Uropygial secretions
Chapter
Full-text available
Progress that has been made in research on the chemical aspects of mammalian semiochemistry over the past decade is discussed on the basis of examples from the most topical problem areas. The chemical characterization of the volatile organic constituents of the urine, anal gland secretions and exocrine gland secretions of rodents, carnivores, proboscids, artiodactyls and primates, and their possible role in the semiochemical communication of these mammals are discussed, with particular emphasis on the advances made in the elaboration of the function of proteins as controlled release carrier materials for the semiochemicals of some of these animals.
Article
Full-text available
Individual recognition has been studied across a number of taxa and modalities; however, few attempts have been made to combine chemical and biological approaches and arrive at a more complete understanding of the use of secretions as signals. We combined behavioral habituation experiments with gas chromatography–mass spectrometry of glandular secretions from the left and right flank gland and midventral gland of the rat-like hamster, Tscheskia triton. We found that females became habituated to one scent and then could discriminate individuals via another scent source from the same individual only when familiar with the scent donor. However, this prior social interaction was not required for females to discriminate different individuals in single-stimulus habituation–dishabituation tests. Chemical analyses revealed a similarity in volatile compounds between the left and right flank gland and midventral gland scents. It appears that individually distinctive cues are integratively coded by a combination of both flank gland and midventral gland secretions, instead of a single scent, albeit animals show different preferences to the novel scent. Our results suggest that odors from the flank and midventral glands may provide information related to individuality and aid individual recognition in this species and confirm that prior interaction between individuals is a prerequisite for rat-like hamsters to form multi-odor memory of a particular conspecific.
Book
We are entering one of the most exciting periods in the study of chemical communication since the first pheromones were identified some 40 years ago. This rapid progress is reflected in this book, the first to cover the whole animal kingdom at this level for 25 years. The importance of chemical communication is illustrated with examples from a diverse range of animals including humans, marine copepods, Drosophila, Caenorhabditis elegans, moths, snakes, goldfish, elephants and mice. It is designed to be advanced, but at the same time accessible to readers whatever their scientific background. For students of ecology, evolution and behaviour, this book gives an introduction to the rapid progress in our understanding of olfaction at the molecular and neurological level. In addition, it offers chemists, molecular and neurobiologists an insight into the ecological, evolutionary and behavioural context of olfactory communication.
Article
In vertebrates, provitamin A carotenoids are converted to retinal by β-carotene-15,15′-dioxygenase. The enzyme activity is expressed specifically in intestinal epithelium and in liver. The intestinal enzyme not only plays an important role in providing animals with vitamin A, but also determines whether provitamin A carotenoids are converted to vitamin A or circulated in the body as intact carotenoids. We have found that a high fat diet enhanced the β-carotene dioxygenase activity together with the cellular retinol binding protein type II level in rat intestines. Flavonols with a catechol structure in the B-ring and 2,6-di-tert-butyl-4-methylphenol inhibited the dioxygenase activity of pig intestinal homogenates and the conversion of β-carotene to retinol in Caco-2 human intestinal cells. Thus, the bioavailability of dietary provitamin A carotenoids might be modulated by the other food components ingested. Regulation of the dioxygenase activity and its relation to the retinoid metabolism as well as to lipid metabolism deserve further study. In contrast to enzymatic cleavage, it is known that both retinal and β-apocarotenals are formed in vitro from β-carotene by chemical transformation, which cleaves conjugated double bonds at random positions under various oxidative conditions. Moreover, recent studies have indicated that the oxidation products formed by chemical transformation might have specific actions on the proliferation of certain cancer cells. We have found that lycopene, a typical nonprovitamin A carotenoid, was cleaved in vitro to acycloretinal, acycloretinoic acid and apolycopenals in a nonenzymatic manner, and that the mixture of oxidation products of lycopene induced apoptosis of HL-60 human promyelocytic leukemia cells. Thus, it is worth evaluating the formation of oxidation products and their biological actions, in order to elucidate the underlying mechanisms of the beneficial effects of carotenoids on human health.
Article
The tail gland of the red fox (Vulpes vulpes) secretes lipids containing volatile terpenes used in social communication. We have analysed lipids extracted from fur of the tail gland, body (flanks) and muzzle of foxes. GC–MS showed a novel group of iso-valerate and tiglate monoesters of alkane-1,2-diols (C18:0–22:0). There was also a larger group of Type II diesters in which a second, longer chain, fatty acid (FA) was attached to the free alcohol group. LC–MS showed the full range of diol diesters, mostly C36:0–50:0, with smaller amounts of the corresponding mono-unsaturated tiglate esters. An additional group of diesters with higher MW (C49:0–62:0) containing two long-chain FA was present in the lipids of body and muzzle fur. After saponification and GC–MS, 98 fatty acids were characterized as their methyl esters. Apart from the C5 FA, most were saturated n-, iso-, anteiso- or other methyl-branched FA (C12:0–28:0) whose structures were determined by a combination of their mass spectra and Kovats retention indices. Several FA have not previously been found in nature or in vertebrates. Thirty-four alkane- 1,2-diols were found as their TMS derivatives, mostly n-, iso- or anteiso-isomers of C16:0–25:0. The tail gland had the greatest amount of wax esters, from a greater variety of FA and diols, but lacked the esters with two long-chain FA.
Article
Bite force is often used as a predictive indicator of an animal's feeding ecology, although the premise that there is a direct link between diet and cranial morphology can be difficult to test empirically. Studies that have examined this question tend to rely on generalizations of a species' diet, and age and sex differences are rarely considered. Red foxes (Vulpes vulpes) are introduced predators in Australia, allowing large sample size collection through culling for comparison of skull morphology (size, morphometry, weight), demographics (age, sex) and diet (stomach contents). Over half (57%) of the 540 animals we sampled were juveniles (<1 year old; dispersing from their natal sites) and most variation in skull morphometry was driven by age; adults had significantly more robust skulls than juveniles, with greater estimated bite force. Sexual dimorphism (body mass and body length) was reflected in longer, heavier skulls of males. We also recorded significant sex and age differences in diet. Sheep carrion comprised 47-65% of diet volume; however, adult females ate less sheep but had more mice and invertebrates in their diet than males or juveniles of both sexes. This dietary separation for adult females does not appear to be directly due to estimated bite force constraints, but probably rather prey availability, which may reflect feeding behaviour and space use patterns. Juveniles (both sexes) showed as much consumption of sheep carrion as adult males, despite their lower estimated bite force than adults. This is the first study that directly compares ontogenetic and sex differences in the diet of a carnivore together with their cranial morphology and estimated bite force, and highlights limitations of inferring diet partitioning from skull morphology alone.
Article
Habitat loss and landscape degradation affect carnivorous mammal populations and the ecosystem services they provide, but these services are poorly assessed in semi-arid ecosystems. In the Ziziphus semiarid scrublands, a priority habitat for conservation in Europe, we investigated how red fox diet relates to habitat loss and landscape alteration. We further evaluated potential top-down effects of foxes on vegetation through seed dispersal and the control of rabbit herbivory (fruit depulpation interfering seed dispersal). By sampling fox scats, we evaluated the variation in fox diet and its relationship to landscape features and rabbit abundance and activity in 17 habitat remnants distributed throughout the Ziziphus habitat range. Fox diet varied, with diet diversity peaking at intermediate land-use diversity, likely as a consequence of fox's ability to use natural foods and human-derived resources. We confirmed that red fox acts as seed disperser for many species and that it might contribute to control rabbit population and its impact on Ziziphus lotus regeneration by interference on seed dispersal, though this needs experimental corroboration. However, these services were affected by landscape degradation. Our results show that red fox is fundamental for Ziziphus semiarid ecosystem providing key ecosystem services which are presently jeopardized by strong landscape degradation.
Article
Tea prepared by infusion of dried leaves of Camellia sinensis (L.) Kuntze, is the second world's most popular beverage, after water. Its consumption is associated with its chemical composition: it influences its sensory and nutritional quality addressing consumer preferences, and potential health benefits. This study aims to obtain an informative chemical signature of the volatile fraction of black tea samples from Ceylon by applying the principles of sensomics. In particular, several high concentration capacity (HCC) sample preparation techniques were tested in combination with GC × GC–MS to investigate chemical signatures of black tea volatiles. This platform, using headspace solid phase microextraction (HS-SPME) with multicomponent fiber as sampling technique, recovers 95% of the key-odorants in a fully automated work-flow. A group 123 components, including key-odorants, technological and botanical tracers, were mapped. The resulting 2D fingerprints were interpreted by pattern recognition tools (i.e. template matching fingerprinting and scripting) providing highly informative chemical signatures for quality assessment.
Article
The Danish pesticide residue monitoring programme evaluates compliance with the maximum residue levels established by the EU and monitors the residue levels in foods to enable an evaluation of the exposure of the Danish population to pesticides. The latter part of the programme included 25 different fruits, vegetables and cereals and processed foods. The commodities were chosen based on their contribution to the intake of pesticides in the Danish population. A total of 17,309 samples were collected during 2004–2011. The monitoring showed that the frequencies of pesticides were higher in samples of foreign origin than in samples of Danish origin both for samples with residues above or below the MRLs. Overall, pesticide residues were more frequently found in fruits and vegetables than the other groups of commodities; fruits had higher frequencies than vegetables. Residues above the MRLs were found in 2.6% of the samples. In plant commodities, 163 different substances were found in measurable concentrations. Residues of more than one pesticide (multiple residues) were found in 27% of all samples. A comparison of the frequencies of pesticide residues in commodities from different countries showed that Danish commodities with a lower frequency of pesticides.
Article
Cyclocitral (I) wird zu ?-Cyclogeraniol (II) reduziert, dessen Oxidation das Diol (III) mit dem 1,2-Diolsystem in cis-Stellung gibt.
Article
Chemical signals play an important role in intraspecific communication and social organization of many animals, but they also may be useful in interspecific recognition. In lizards, chemical signals are often contained in femoral gland secretions, of which composition may vary between species and populations. This may be especially important in recognition and reproductive isolation between closely related species. We analyzed by gas chromatography-mass spectrometry (GC-MS) the lipophilic fraction of femoral gland secretions of two closely related wall lizard species, Podarcis bocagei and Podarcis carbonelli to test for possible interspecific differences in chemical composition. We found 56 lipophilic compounds in femoral gland secretions of male P. bocagei and 60 in P. carbonelli. The main compounds were steroids and waxy esters, but we also found carboxylic acids and their esters, alcohols, amydes, aldehydes, squalene, ketones and furanones. There were significant differences between species with respect to the number and relative proportions of compounds. Differences in chemical composition might be a consequence of phylogenetic differences per se, but they could also be explained by ecological adaptation to different microclimatic conditions. These differences in chemical profiles may explain the known chemosensory interspecific recognition between these two lizards, contributing to their reproductive isolation.
Article
Focusing exclusively on the chemically mediated interactions between vertebrates, including humans and other animals and plants, this monograph combines information from widely scattered technical literature in different disciplines. It will be an indispensable reference for undergraduates, graduate students and researchers interested in how chemical signals are used for inter- and intra-specific communication in vertebrates. © Cambridge University Press 2006 and Cambridge University Press, 2009.
Article
Covering: 1950 to 2015We compiled a data set of the compounds that terrestrial vertebrates (amniotes) use to send chemical signals, and searched for relationships between signal compound properties and signal function. Overall, relationships were scarce and formed only small-scale patterns. Terrestrial vertebrate signalling compounds are invariably components of complex mixtures of compounds with diverse molecular weights and functionalities. Signal compounds with high molecular weights (MWs) and low vapour pressures, or that are bound to carrier proteins, are detected during direct contact with the source of the signal. Stable compounds with aromatic rings in their structures are more common in signals of social dominance, including territoriality. Aldehydes are emitted from the sender’s body rather than from scent marks. Lipocalin pheromones and carriers have a limited range of MWs, possibly to reduce the metabolic costs of their biosynthesis. Design constraints that might channel signal chemistry into patterns have been relaxed by amniote behavior and biochemistry. Amniote olfaction has such a high sensitivity, wide range and narrow resolution that signal detection imposes no practical constraints on the structures of signalling molecules. Diverse metabolic pathways in amniotes and their microbial commensals produce a wide variety of compounds as chemical signals and as matrix compounds that free signal components from the constraints of stability, vapor pressure, species-specificity etc. that would otherwise constrain what types of compound operate optimally under different conditions.
Article
Carotenoids have traditionally been subscribed to their role as accessory pigments in photosynthesis. However, the large and growing body of literature investigated on the field have revealed that carotenoids fulfill a plethora of essential roles in plants but also in animals and in humans. Recent studies emphasizing the functional role of molecules derived from carotenoids oxidation as β-cyclocitral or dihydroactinidiolide led to a renewed interest, opening a new era for the carotenoids research. This review brings together the knowledge obtained so far regarding diversity and functions of carotenoids, highlighting carotenoids versatility and the remarkable parallel roles of carotenoids in both plants and in animals. Evolutionary aspects and the responses of carotenoids to biotic and abiotic stresses are discussed. Furthermore, we outline the way in which one can understand the environmental regulation to enhance carotenoid content in food. In addition, an up-to-date overview of carotenoids as elements of information storage system for the responses to environmental signals is provided together with suggestions for future directions of research
Article
Significance A long-standing question in pheromone biosynthesis is the origin of the mevalonate pathway-derived precursor to frontalin, a key pheromone to the successful mass attack of conifer hosts by Dendroctonus bark beetles. Using a combination of genome and transcriptome analysis, functional characterization of expressed proteins, RNA interference, and transcript and metabolite analysis, we provide evidence that frontalin in the mountain pine beetle ( Dendroctonus ponderosae Hopkins) originates from the 20-carbon geranylgeranyl diphosphate rather than from 10-carbon geranyl diphosphate or 15-carbon farnesyl diphosphate. This result opens the way to study the later steps in frontalin biosynthesis.
Article
Understanding the role of urine marking in the territorial systems of wild mammals can be difficult, especially for nocturnal cryptic species. Even for common species, such as the red fox Vulpes vulpes, a comprehensive analysis of seasonal and sex differences has not been carried out. Using 6 years of infra-red video monitoring, we compared marking rates between months and between sexes. Urine marking was significantly lower during summer (June–August). Males urine marked significantly more frequently than females during late summer and autumn, but not winter. Males marked more frequently than females also during March. There was no increase during the breeding season for either sex. Our results correlate with previous partial data but demonstrate how urine marking rates vary across the year. They also further support the greater role of males in fox territorial maintenance. Urine marking is lowest during summer when territorial intrusions are least, whilst the higher male urine marking rate in March reflects the period when females are denning. Overall, our results provide the first comprehensive analysis of red fox urine marking rates, contributing to a greater understanding of territoriality and olfactory communication.
Article
Sexually experienced male rats display penile erections when exposed to faeces from mammalian females in oestrus (Rampin et al., Behav Brain Res, 172:169, 2006), suggesting that specific odours indicate female receptiveness across species. However, it is unknown to what extent the sexual response observed results from an odorous conditioning acquired during sexual experience. We tested the behavioural response of male Brown Norway rats both when sexually naïve and experienced to four odours, including oestrous rat faeces and 6-methyl-5-hepten-2-one (methylheptenone; a molecule found in higher concentrations during oestrus in female rats, foxes and horses). Odour had a significant effect on the sexual response of the naïve rats, with oestrus faeces provoking significantly more erections than herb odour, and with methylheptenone and di-oestrus faeces being intermediate. This indicates that sexually naïve male rats have an unconditioned ability to detect oestrous mediated via odour. After gaining sexual experience, the response to methylheptenone, di- and oestrus faeces was significantly higher than that observed with herb odour. These results strongly suggest that methylheptenone is part of the odorous bouquet of oestrus and contributes to the olfactory determination of female receptiveness.
Article
There are approximately 40-50 carotenoids in commonly consumed fruits and vegetables in a typical U.S. diet. These can be divided into carotenoid epoxides, mono- and dihydroxycarotenoids, hydrocarbon carotenoids, and carotenol acyl esters. However, among these, only a selected group of carotenoids are routinely found in human plasma, breast milk, major organs, and ocular tissues. In addition, several carotenoid metabolites have also been isolated and characterized from human plasma, tissues, and ocular tissues. The proposed metabolic transformation of carotenoids in humans will be discussed. Dietary carotenoids and their metabolites have been implicated in the prevention of cancer, cardiovascular dis- ease, and age-related macular degeneration (AMD). An approach for the development of a nutritional supplement that is based on the distribution of carotenoids and their metabolites in humans will be discussed.
Article
This paper describes a novel one-step synthesis of γ-lactones by the reaction of manganic and other higher valent metal carboxylates with readily available olefins and carboxylic acids. A free radical mechanism involving the selective generation and oxidation of organic free radicals is presented.
Article
More than 160 constituents were identified in a commercial Boronia absolute. The main constituents are β-ionone, (Z)-heptadec-8-ene, 8-hydroxylinalyl esters, methyl (Z,E)-4-(geranyloxy)cinnamates, methyl (Z,E)-4-(5-hydroxygeranyloxy)cinnamates, N-[2-(4-prenyloxyphenyl)ethyl]tiglamide and 3-hydroxymegastigm-7-en-9-one, which are even recognizable in the 400 MHz 1H-NMR spectrum of the dewaxed absolute.
Article
Carotenoids are one of the major food micronutrients in human diets and the overall objective of this review is to re-examine the role of carotenoids in human nutrition. We have emphasized the attention on the following carotenoids present in food and human tissues: β-carotene, β-cryptoxanthin, α-carotene, lycopene, lutein and zeaxanthin; we have reported the major food sources and dietary intake of these compounds. We have tried to summarize positive and negative effects of food processing, storage, cooking on carotenoid content and carotenoid bioavailability. In particular, we have evidenced the possibility to improve carotenoids bioavailability in accordance with changes and variations of technology procedures.
Article
Black-tailed deer (Odocoileus hemionus columbianus) discriminate between the geometric isomers of a lactone used as a pheromone by the species. They react strongly to (Z)-4-hydroxy-6-dodeceonic acid lactone, which occurs in their tarsal scent, but the response to theE isomer did not differ from the response to the solvent. The isomers were applied to one member of a group of freely interacting deer, and the sniffing, licking, and following responses were recorded. The synthesis of the geometric isomers of the lactone is described.
Article
Urine samples collected from dominant and subordinate male white-tailed deer during the breeding and nonbreeding season were analyzed by combined gas chromatography–mass spectrometry (GC-MS). Fifty-five volatiles were found in measurable quantities. Ketones were most numerous, followed by alcohols and alkanes. Nine compounds were common to both dominants and subordinates during the breeding season. Of these nine, three were present in higher concentrations in dominants, and six were higher in subordinates. During the breeding season, nine compounds were found exclusively in the urine of dominants, whereas 19 compounds were found exclusively in the urine of subordinates. Concentrations of several compounds were dependent on the time of year (breeding vs. nonbreeding season). Differences in compound presence and concentration may produce a rank-specific odor, although we suggest that differing concentrations of these suites of compounds may be more important for the identification of social status than the presence of individual compounds. Since mature male white-tailed deer urinate on their tarsal glands frequently during the breeding season, this behavior may allow a deer to simultaneously scent-mark its environment and carry intraspecific cues indicative of social status.
Article
The tail gland of canids is a hepatoid glandular organ surrounded and penetrated by powerful hair erector muscles squeezing out its lipoprotein secretion onto the skin surface. The gland is most developed in solitary species (Arctic, red, and corsac foxes) where it is represented by powerful glandular layer with large secretion containers—cisterns. It is less developed in the jackal; there are cisterns but glandular lobes do not merge into a layer. In the raccoon dog, wolf, and domestic dog the gland is composed of small lobes without cisterns. Hepatoid glands of the tail gland are represented by two histological variants distinguished by the presence or absence of hydrophobic lipids in the secretory cells. The excretory ducts are formed by lipid transformation of the cellular bands.
Article
Putrescine (1,4-diaminobutane) and cadaverine (1,5-di-aminopentane) were identified in the anal sac secretions of the red fox,Vulpes vulpes, and of the lion, Panthera leo. Anal sac secretion samples obtained over a period of 10 weeks by sampling from within each sac of each of 6 captive foxes were analyzed and putrescine, cadaverine, and volatile fatty acid compositions and secretion pH values recorded. A significant (P < 0.001)="" negative="" correlation="" of="" ph="" (range="" 6.5–9.4)="" with="" total="" volatile="" fatty="" acid="" concentration="" was="" observed.="" secretion="" compositions="" are="" discussed="" in="" the="" context="" of="" a="" fermentation="" hypothesis="" of="" chemical="" recognition.="" secretion="" samples="" could="" not="" be="" unambiguously="" assigned="" to="" particular="" foxes="" on="" the="" basis="" of="" simple="" comparisons="" of="" volatile="" fatty="" acid="" profiles="" alone.="" composition="" differences="" were="" noted="" between="" secretions="" obtained="" at="" a="" given="" time="" from="" corresponding="" right="" and="" left="">
Article
A control aqueous solution containing alcohol and polyethylene glycol, and a test solution with the addition of a mixture of eight volatile synthetic compounds identified in red fox urine, Were alternately placed on man-made mounds of fresh snow during January and February, the foxes' courtship season. The foxes preferentially marked those mounds treated with the test solution in the two experimental areas (P < 0.05 and <0.0001). It is concluded that one or more of the volatile substances induces mound marking in this species.
Article
The supracaudal gland of the red fox consists of both tubular apocrine sweat glands and massively developed sebaceous glands. The gland is characterized by a high level of histochemically demonstrable hydroxysteroid dehydrogenase activity (particularly -3 HSD) and by the presence of naturally fluorescent photolabile sebum constituents. Evidence suggests that these components may be carotenoid. Results are presented in the context of histological observations and are discussed in relation to scent production.
Chapter
The use of anomalous X-ray scattering of light elements like sulfur and phosphorus is of particular interest in biological structure research. These elements serve as native labels in proteins, nucleic acids and membranes. Their medium scattering power is drastically changed at their K absorption edges at wavelengths between 5 and 6 Å where X-ray absorption excludes the use of open air diffractometers. The construction of a new diffractometer tunable to wavelengths between 1.2 and 7 Å is presented. First results of anomalous scattering from sulfur in bacteriorhodopsin near the K absorption edge have been obtained recently. Their possible impact on crystallography will be considered. A comparison with nuclear spin dependent neutron scattering is given.
Article
Volatile organic compounds (VOCs) in fermented honeybush, Cyclopia subternata, were sampled by means of a high-capacity headspace sample enrichment probe (SEP) and analyzed by gas chromatography-mass spectrometry (GC-MS). Stereochemistry was determined by means of enantioselective GC-MS with derivatized β-cyclodextrin columns as chiral selectors. A total of 183 compounds, the majority of which are terpenoids (103; 56%), were identified by comparing their mass spectra and retention indices with those of reference compounds or tentatively identified by comparison with spectral library or literature data. Of these compounds, 37 were determined by gas chromatography-olfactometry (GC-O), using detection frequency (DF) and aroma extract dilution analysis (AEDA), to be odor-active (FD ≥ 2). (E)-β-Damascenone, (R/S)-linalool, (E)-β-damascone, geraniol, (E)-β-ionone, and (7E)-megastigma-5,7,9-trien-4-one were identified with the highest FD factors (≥512). The odors of certain compounds, that is, (6E,8Z)-megastigma-4,6,8-trien-3-one, (6E,8E)-megastigma-4,6,8-trien-3-one, (7E)-megastigma-5,7,9-trien-4-one, 10-epi-γ-eudesmol, epi-α-muurolol, and epi-α-cadinol, were perceived by GC-O assessors as typically honeybush-like.
Article
In humans, varying amounts of absorbed β-carotene are oxidatively cleaved by the enzyme β,β-carotene 15,15'-monooxygenase 1 (BCMO1) into two molecules of all-trans-retinal. The other carotenoid cleavage enzyme β,β-carotene 9',10'-dioxygenase (BCDO2) cleaves β-carotene at the 9',10' double bond forming β-apo-10'-carotenal and β-ionone. Although the contribution of BCDO2 to vitamin A formation has long been debated, BCMO1 is currently considered the key enzyme for retinoid metabolism. Furthermore, BCMO1 has limited enzyme activity towards carotenoids other than provitamin A carotenoids, whereas BCDO2 exhibits a broader specificity. Both enzymes are located at different sites within the cell, with BCMO1 being a cytosolic protein and BCDO2 being located in the mitochondria. Expression of BCMO1 in tissues other than the intestine has recently revealed its function for tissue-specific retinoid metabolism with importance in embryogenesis and lipid metabolism. On the other hand, biological activity of BCDO2 metabolites has been shown to be important in protecting against carotenoid-induced mitochondrial dysfunction. Single-nucleotide polymorphisms (SNPs) such as R267S and A379V in BCMO1 can partly explain inter-individual variations observed in carotenoid metabolism. Advancing knowledge about the physiological role of these two enzymes will contribute to understanding the importance of carotenoids in health and disease.
Article
This review focuses on plant carotenoids, but it also includes progress made on microbial and animal carotenoid metabolism to better understand the functions and the evolution of these structurally diverse compounds with a common backbone. Plants have evolved isogenes for specific key steps of carotenoid biosynthesis with differential expression profiles, whose characteristic features will be compared. Perhaps the most exciting progress has been made in studies of carotenoid cleavage products (apocarotenoids) with an ever-expanding variety of novel functions being discovered. This review therefore covers structural, molecular genetic and functional aspects of carotenoids and apocarotenoids alike. Apocarotenoids are specifically tailored from carotenoids by a family of oxidative cleavage enzymes, but whether there are contributions to their generation from chemical oxidation, photooxidation or other mechanisms is largely unknown. Control of carotenoid homeostasis is discussed in the context of biosynthetic and degradative reactions but also in the context of subcellular environments for deposition and sequestration within and outside of plastids. Other aspects of carotenoid research, including metabolic engineering and synthetic biology approaches, will only be covered briefly.
Article
Xanthophyll carotenoids, such as lutein, zeaxanthin and β-cryptoxanthin, may provide potential health benefits against chronic and degenerative diseases. Investigating pathways of xanthophyll metabolism are important to understanding their biological functions. Carotene-15,15'-monooxygenase (CMO1) has been shown to be involved in vitamin A formation, while recent studies suggest that carotene-9',10'-monooxygenase (CMO2) may have a broader substrate specificity than previously recognized. In this in vitro study, we investigated baculovirus-generated recombinant ferret CMO2 cleavage activity towards the carotenoid substrates zeaxanthin, lutein and β-cryptoxanthin. Utilizing HPLC, LC-MS and GC-MS, we identified both volatile and non-volatile apo-carotenoid products including 3-OH-β-ionone, 3-OH-α-ionone, β-ionone, 3-OH-α-apo-10'-carotenal, 3-OH-β-apo-10'-carotenal, and β-apo-10'-carotenal, indicating cleavage at both the 9,10 and 9',10' carbon-carbon double bond. Enzyme kinetic analysis indicated the xanthophylls zeaxanthin and lutein are preferentially cleaved over β-cryptoxanthin, indicating a key role of CMO2 in non-provitamin A carotenoid metabolism. Furthermore, incubation of 3-OH-β-apo-10'-carotenal with CMO2 lysate resulted in the formation of 3-OH-β-ionone. In the presence of NAD(+), in vitro incubation of 3-OH-β-apo-10'-carotenal with ferret hepatic homogenates formed 3-OH-β-apo-10'-carotenoic acid. Since apo-carotenoids serve as important signaling molecules in a variety of biological processes, enzymatic cleavage of xanthophylls by mammalian CMO2 represents a new avenue of research regarding vertebrate carotenoid metabolism and biological function.