Scent Compounds Research Articles

Molecular cloning and characterization of UDP-glucose: Volatile benzenoid/phenylpropanoid glucosyltransferase in petunia flowers

Volatile benzenoids/phenylpropanoids are characteristic scent compounds in petunia flowers and are reported to be stored as glycosides in the vacuoles of petal cells. Here, we used transcriptomics and co-expression approaches with volatile benzenoid/phenylpropanoid biosynthetic genes to identify three petunia genes (UGT85A96, UGT85A97, and UGT85A98) encoding UDP-glycosyltransferase. The analyses of spatiotemporal gene expression revealed that all UGT85 genes were highly expressed in floral tissues such as petals and pistils. Functional characterization of recombinant UGT85A96 and UGT85A98 proteins expressed in Escherichia coli showed that UGT85A98 could transfer a glucosyl moiety from UDP-glucose to the hydroxyl group of various substrates including volatile benzenoids/phenylpropanoids, terpene alcohol, flavonoids, and C6 alcohol, whereas UGT85A96 specifically catalyzes the glucosylation of 2-phenylethanol and benzyl alcohol. This report describes the first experimental evidence to identify UGT enzymes that catalyze the glycosylation of volatile benzenoids/phenylpropanoids in petunia flowers.

Floral Scent Composition and Fine-Scale Timing in Two Moth-Pollinated Hawaiian Schiedea (Caryophyllaceae).

Floral scent often intensifies during periods of pollinator activity, but the degree of this synchrony may vary among scent compounds depending on their function. Related plant species with the same pollinator may exhibit similar timing and composition of floral scent. We compared timing and composition of floral volatiles for two endemic Hawaiian plant species, Schiedea kaalae and S. hookeri (Caryophyllaceae). For S. kaalae, we also compared the daily timing of emission of floral volatiles to evening visits of their shared pollinator, an endemic Hawaiian moth (Pseudoschrankia brevipalpis; Erebidae). The identity and amount of floral volatiles were measured in the greenhouse during day and evening periods with dynamic headspace sampling and GC-MS (gas chromatography – mass spectrometry). The timing of emissions (daily rise, peak, and fall) was measured by sampling continuously for multiple days in a growth chamber with PTR-MS (proton transfer reaction mass spectrometry). Nearly all volatiles detected underwent strong daily cycles in emission. Timings of floral volatile emissions were similar for S. kaalae and S. hookeri, as expected for two species sharing the same pollinator. For S. kaalae, many volatiles known to attract moths, including several linalool oxides and 2-phenylacetaldehyde, peaked within 2 h of the peak visitation time of the moth which pollinates both species. Floral volatiles of both species that peaked in the evening were also emitted several hours before and after the brief window of pollinator activity. Few volatiles followed a daytime emission pattern, consistent with increased apparency to visitors only at night. The scent blends of the two species differed in their major components and were most distinct from each other in the evening. The qualitative difference in evening scent composition between the two Schiedea species may reflect their distinct evolutionary history and may indicate that the moth species uses several different floral cues to locate rewards.

Floral pigment-scent associations in eight cut rose cultivars with various petal colors

The associations between petal pigments and scent compounds of Rosa hybrida were determined in eight commercial cultivars with different petal-colors, visually classified as four petal-color groups: ‘Beast’ and 'Marilyn Monroe' in white (W), ‘Good Time’ and ‘Penny Lane’ in yellow (Y), ‘Ahoi’ and ‘Pink Condor’ in pink (P), and ‘Pearl Red’ and ‘Vital’ in red (R). The petal pigments were distinct by visual petal color polymorphs. Yellow petals contained only carotenoids and unusually large amounts of β-carotenes as their primary pigments, whereas white ones included minimal levels of carotenoids. As expected, pink and red flowers had cyanin as the major anthocyanin. The amount of cyanin in petals was significantly higher in the red petals. Unlike petal pigments, the scents were abundant in white and yellow flowers, containing both phenolic and terpene compounds. The pink and red flowers, on the other hand, were scented with only phenolics as represented by 2-phenylethanol and 3,5-dimethoxytoluene, which existed in all eight cultivars. The amount of detected scent was up to six times higher in the white or yellow flowers than in the pink or red ones. A principal component analysis (PCA) with all detected pigments and scents resulted in classifying eight cultivars as three independent groups: (GI) ‘Beast’, (GII) ‘Good Time’, ‘Penny Lane’, and ‘Marilyn Monroe’, and (GIII) ‘Ahoi’, ‘Pink Condor’, ‘Pearl Red’, and ‘Vital’. ‘Marilyn Monroe’ (W) belonged to GII with yellow cultivars, not to GI with ‘Beast’ (W). The PCA coordinates of pink and red cultivars were so close that they belonged to the same group, GIII. With this information, we know that rose petal colors may differ in terms of their pigment and scent profiles.

Composition and Biosynthesis of Scent Compounds from Sterile Flowers of an Ornamental Plant Clematis florida cv. 'Kaiser'.

Clematisflorida is a popular ornamental vine species known for diverse colors and shapes of its flowers but not for scent. Here we investigated the composition and biosynthesis of floral scent in ‘Kaiser’, a fragrant cultivar of C. florida that has sterile flowers. Volatile profiling revealed that flowers of ‘Kaiser’ emit more than 20 compounds, with monoterpenes being most abundant. Among the three floral organs, namely sepals, transformed-petals, and ovaries, ovaries had the highest rates of total volatile emission. To determine the molecular mechanism underlying floral scent biosynthesis in ‘Kaiser’, we sequenced a flower transcriptome and searched the transcriptome for terpene synthase genes (TPSs), which are key genes for terpene biosynthesis. Among the TPS genes identified, three were putative intact full-length genes and were designated CfTPS1, CfTPS2, and CfTPS3. Phylogenetic analysis placed CfTPS1, CfTPS2, and CfTPS3 to the TPS-g, TPS-b, and TPS-a subfamily, respectively. Through in vitro enzyme assays with Escherichia coli-expressed recombinant proteins, both CfTPS1 and CfTPS2 were demonstrated to catalyze the conversion of geranyl diphosphate to linalool, the most abundant constituent of C. florida floral scent. In addition, CfTPS1 and CfTPS2 produced the sesquiterpene nerolidol from (E,E)-farnesyl diphosphate. CfTPS3 showed sesquiterpene synthase activity and produced multiple products in vitro. All three CfTPS genes showed higher levels of expression in sepals than those in transformed-petals and ovaries. Our results show that despite being sterile, the flowers of ‘Kaiser’ have normal mechanisms for floral scent biosynthesis that make the flowers fragrant.

Geraniol quality improvement on citronella oil as raw material for making anti-bacterial perfumes

In this study, optimization was carried out to increase the levels of geraniol compounds present in citronella oil using vacuum distillation. Geraniol is a compound that has been legalized by IFRA (Fragrance International Research Association) as a scent compound, Geraniol has been studied in addition to having a pleasant fragrance, geraniol is also very effective in inhibiting bacterial growth. So geraniol is a reference to use it as formulated as a raw material for anti-bacterial products, but the levels of geraniol in citronella oil are still very low. This is what encourages the processing of fragrant citronella oil to be processed, by increasing geraniol levels using a vacuum distillation method, with variations in pressure: 8mmHg, 6mmHg, 4mmHg, 1mmHg during the operating time: 20 minutes; 40 minutes; 60 minutes and until Final boiling point. The samples were analysed using GC-MS (Gas Chromatography of Mass Spectrometry, FTIR (Fourier Transform Infra-Red Spectrophotometer), refractive index, and bacterial testing of research products. The results showed that higher temperature usage had an effect on increasing geraniol levels and showed that This vacuum distillation method is quite effective. Geraniol concentrations before and after isolation increased by 38%. namely from 20.32% to 57.39%. This shows that this method is quite effective in increasing geraniol concentrations in fragrant citronella oil. Analysis of FTIR shows 3365.78 cm-1 according to the hydroxyl polymer group (OH).

Identity and localization of floral scent components in an androdioecious species, Chionanthus retusus (Oleaceae)

Chionanthus retusus Lindl. & Paxton (Oleaceae) is an androdioecious species, in which male individuals coexist with hermaphroditic individuals. Even though the floral scent dimorphism of dioecious taxa has been reported elsewhere, little is known about the floral scent compounds of androdioecious species. The aim of the present study was to elucidate the identity and localization of floral scent components in C. retusus in both male and hermaphrodite. The headspace of whole flowers exhibited quantitative and qualitative floral scent dimorphism. Among several constituents, including phenylethyl alcohol, benzeneacetonitrile, 2-hexen-1-ol were the main fragrance component of both sexual morphotypes. In particular, the abundance of phenylethyl alcohol (2-phenylethanol), which is one of the compounds in pollen and pollenkitt, in both sexual morphotypes might provide indirect evidence for the viability and functionality of pollen grains. However, 3-hexen-1-ol, 1-hexanol, 3-hexenyl 2-metylbutanoate, alloaromadendrene, and farnesol were only detected in hermaphrodites. These patterns of floral scent difference suggest that several compounds solely detected in each sexual type are associated with specific reproductive organs. Comparative micromorphological and ultrastructural studies of floral surfaces (e.g. floral stomata, calyx glands) and pollen grains (especially pollenkitt) revealed that all represent a putative secretory structures and materials.

Seasonal and diel variations in scent composition of ephemeral Murraya paniculata (Linn.) Jack flowers are contributed by separate volatile components

Scent profile of the ephemeral nocturnal floral species Murraya paniculata was characterized to assess diel and seasonal variability. The floral fragrance was found to constitute a characteristic set of 15 major volatile organic compounds (VOCs) dominated by benzenoids, terpenoids and phenylethanoids. Strong diel variability was detected due to dominantly endogenous regulation of 2-phenylethanol and (E)-β-ocimene emission levels, along with temperature-correlated emission rates of 2-phenylethanal, methyl benzoate, methyl anthranilate and germacrene D, resulting in high diurnal contents of the former two VOCs and high nocturnal contents of the latter four VOCs in the fragrance. Significant seasonal variation was contributed by a separate suite of VOCs including linalool, nonanal, decanal, methyl salicylate and methyl palmitate. Higher abundances of these components in certain seasons were found to add subtle variations in the strong diurnal/nocturnal division in the scent profile. Emission rate of linalool is endogenously regulated on a seasonal scale, but that of (E,E)-α-farnesene was maintained at consistent proportions even if correlated to temperature variations. It was concluded that the two sub-sets of major scent compounds, each comprising six VOCs, are adaptive responses such that the strong day/night component of variation in maintained along with necessary physiological adjustments to changing seasons. The varying effects of climatic factors on the 15 major VOCs indicated different regulating mechanisms comprising environmental and endogenous mechanisms in different degrees.

Selection of key floral scent compounds from fruit and vegetable crops by honey bees depends on sensory capacity and experience

Flowers have complex odours often comprising hundreds of volatile compounds. Floral scents are species-specific, and vary also among populations, varieties, sexes or lines, as well as with phenology. Honey bees, Apis mellifera, generally associate only a few key compounds among the complex floral scent with the food reward which guides their foraging choices. How these key compounds are selected remains partially unexplained, despite their crucial role in influencing foraging. Using electrophysiological techniques and behavioural assays, we identified the key bioactive compounds that bees detected with their antennae and that were associated with appetitive responses from four fruit crops and three vegetable crops. Three quantities of identified key volatile compounds were assayed with the two methods in each of four different seasons with experienced foragers. Whether the selection of these key compounds is determined by the sensory capability of the bee or influenced by its foraging experience was assessed by comparing experienced and naïve bees. Our results showed that experienced foragers were electrophysiologically-sensitive to a specific set of key compounds for each crop, independent of variation in quantity among several varieties. Experienced foragers responded to these compounds in all seasons, with increased electrophysiological amplitude with increasing quantities. Behavioural appetitive responses varied amongst compounds and seasons, revealing preferences based on associative learning. Naïve bees that were exposed to compounds and subsequently learned them, tended to be overall more sensitive. We discuss our results based on the identity of each bioactive compound and their presence in nature. Preferences for specific floral compounds based on sensory biases exist and associative learning may reinforce behavioural attraction depending on foraging experience in each season.

Human scent samples for chemical analysis

This study is focused on finding an optimal preparation of the human scent samples for their detailed chemical analysis in connection with the possible forensic identifications of human individuals in the future. At the present time, the scent identification of people is carried out nearly exclusively using specially trained dogs. It is assumed that the human scent contains a certain group of compounds which allows the identification of people, the so-called human scent signature; however, its chemical composition is completely unknown, as of now. The principal problem of human scent studies consists in the very low concentrations of thousands of the scent compounds, whereas their relative concentrations are usually dramatically different. It seems to be obvious that the most appropriate analytical technique for these thousands of different chemical compounds is GC/MS. However, it is also necessary to find the most suitable sorbent material for human scent collection, an extraction solvent, and a pre-concentration technique. The selection of the appropriate gas chromatographic method is also important to achieve the optimal resolution of the targeted compounds. Of course, in the first instance, it is necessary to decide what it means “the most suitable” for human scent chemical analysis.

Volatile composition and classification of Lilium flower aroma types and identification, polymorphisms, and alternative splicing of their monoterpene synthase genes

Lily is a well-known ornamental plant with a diversity of fragrant types. Basic information on lily floral scent compounds has been obtained for only a few accessions, and little is known about Lilium aroma types, the terpene synthase genes that may play roles in the production of key volatiles, or the range of monoterpenes that these genes produce. In this study, 41 cultivars were analyzed for volatile emissions, and a total of 46 individual volatile compounds were identified, 16 for the first time in lilies. Lily accessions were classified into six groups according to the composition of major scent components: faint-scented, cool, fruity, musky, fruity-honey, and lily. Monoterpenes were one of the main groups of volatiles identified, and attention was focused on terpene synthase (TPS) genes, which encode enzymes that catalyze the last steps in monoterpene synthesis. Thirty-two candidate monoterpene synthase cDNAs were obtained from 66 lily cultivars, and 64 SNPs were identified. Two InDels were also shown to result from variable splicing, and sequence analysis suggested that different transcripts arose from the same gene. All identified nucleotide substitution sites were highly correlated with the amounts of myrcene emitted, and InDel site 230 was highly correlated with the emission of all major monoterpenoid components, especially (E)-β-ocimene. Heterologous expression of five cDNAs cloned from faint-scented and strong-scented lilies showed that their corresponding enzymes could convert geranyl diphosphate to (E)-β-ocimene, α-pinene, and limonene. The findings from this study provide a major resource for the assessment of lily scent volatiles and will be helpful in breeding of improved volatile components.

Pollination elicits an accelerated reduction in nocturnal scent emission by flowers of the dioecious herb Silene latifolia

More than 85% of plants rely on biotic pollen vectors attracted by olfactory or visual signals. While these signals are beneficial for plant reproduction, they are also costly in terms of resource investment, and may involve additional costs related to herbivore attraction, transmission of diseases, and increased transfer of self-pollen among flowers of an individual plant. Given the potential costs of signalling to pollinators, we hypothesized that plants should cease signalling to pollinators as soon as the costs of being attractive exceed the benefits. Here, we used the herb Silene latifolia Poir., which is pollinated by the nocturnal seed-predator Hadena bicruris, to investigate the possible reduction of scent emission after pollination. We compared the progressive decrease of scent and attractive compound emission between pollinated and unpollinated flowers on an hourly basis, overnight. We found that total scent emission decreased significantly faster over time for pollinated than for non-pollinated flowers. Our findings suggest that the costs of maintaining the attractiveness of pollinated flowers of Silene latifolia exceed the benefits, which could be linked with the risks of parasitism.

Floral Scent Variation in the Heterostylous Species Gelsemium sempervirens.

Gelsemium sempervirens (L.) W.T. Aiton, a distylous woody vine of the family Gelsemiaceae, produces sweetly fragrant flowers that are known for the toxic alkaloids they contain. The composition of this plant’s floral scent has not previously been determined. In this study, the scent profiles of 74 flowers obtained from six different wild and cultivated populations of G. sempervirens were measured by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). There were 81 volatile organic compounds identified and characterized as benzenoids, terpenoids, fatty acid derivatives, and yeast associated compounds. The most abundant compound was benzaldehyde (23–80%) followed by ethanol (0.9–17%), benzyl benzoate (2–15%), 4-anisaldehyde (2–11%), (Z)-α-ocimene (0–34%), and α-farnesene (0.1–16%). The impacts of geographic location, population type (wild or cultivated), and style morph (L = long, S = short) on scent profile were investigated. The results showed no relationship between geographic location or population type and volatile organic compounds (VOC) profile, but did show a significant scent profile difference between L and S morphs based on non-metric multidimensional scaling (NMDS) using Bray-Curtis similarity indices. The L morphs contained higher amounts of benzenoids and the S morphs contained higher amounts of terpenoids in their scent profiles. The L morphs also produced a higher total abundance of scent compounds than the S morphs. This study represents the first floral scent determination of G. sempervirens finding significant variation in scent abundance and composition between style morphs.

Isolation of 2-phenylethanol biosynthesis related gene and developmental patterns of emission of scent compounds in Persian musk rose (Rosa moschata Herrm.)

Abstract The molecular properties of 2-phenylethanol were investigated in the single petals of Persian Musk rose at four floral developmental stages. The chemical compositions of the floral scent emissions were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). In this plant, the relative percentage of 2-phenylethanol increased as flowers developed. In the early stage of flower development, the patterns of emission of 2-phenylethanol were very low and then progressively increased reaching its highest value at full bloom stage. The partial CDS of phenyl acetaldehyde reductase (PAR) were isolated in the petals of Persian musk rose. Moreover, the expression pattern of RmPAR showed a significant difference during flower developmental stages and floral organ parts of Rosa moschata. The expression level of RmPAR constantly decreased from the budding stage (stage 1) to the full bloom stage (stage 3); It is reached at the highest level in the budding stage and rapidly decreases in the full bloom stage, and then increases again in the senescence stage (stage 4). In addition, the highest expression level of RmPAR was in the stamen and slightly higher in the petal, and the expression amount in the pistil was about half that in the stamen. Nevertheless, in the calyxes, RmPAR was lowly expressed.

Diversity of floral scent of tulips

Tulips have a variety of floral scents. Although the charm of tulip is a variety of colours and shapes, there are a few fragrant cultivars. When you smell the tulip scent well, you can feel various scents such as citrus-like, honey-like, green-like. We selected 86 cultivars of tulip that have characteristics floral odor. About 183 scent compounds ranging from terpenoids and benzenoids to fatty acid-derivatives were detected by GC-MS analysis. The major scent compounds were five monoterpenoids (eucalyptol, linalool, d-limonene, trans-b-ocimene, and a-pinene), four sesquiterpenoids (caryophyllene, a-farnesene, geranyl acetone, and b-ionone), six benzenoids (acetophenone, benzaldehyde, benzyl alcohol, 3,5-dimethoxytoluene, methyl salicylate, and 2-phenylethanol), and five fatty acid derivatives (decanal, 2-hexenal, cis-3-hexenol, cis-3-hexenyl acetate, and octanal). Tulip cultivars were classified into nine groups according to the composition of major scent components and sensory assessment of a living flower: group 1, anise (7 cultivars, e.g. ‘Candy Prince’); group 2, citrus (21 cultivars, e.g. ‘Advance’); group 3, fruity (14 cultivars, e.g. ‘Sane’); group 4, green (16 cultivars, e.g. ‘Cum Laude’); group 5, herbal (16 cultivars, e.g. ‘Davenport’); group 6, herbal-honey (1 cultivar, ‘Nagoriyuki’); group 7, rosy (2 cultivars, e.g. ‘Monte Rosa’); group 8, spicy (7 cultivars, e.g. ‘Ben van Zanten’); and group 9, woody (2 cultivars, e.g. ‘Queen of night’). It is thought that the diversity of floral scent of tulips is cause.

Nocturnal floral scent profiles of Myrtaceae fruit crops

Communication between plants and nocturnal pollinators in low light conditions is mainly guided by floral scents, which is well documented for plants pollinated by bats, moths, and beetles. Just recently, nocturnal bees have been added to the list of pollinators known to respond to floral scents of their host plants. Little is known about the floral scent chemistry of plants visited and pollinated by nocturnal bees. Among these plants are economically important fruit crops of the family Myrtaceae. We aimed to analyze the nocturnal floral scent profiles of 10 species of Myrtaceae (only diurnal P. cattleianum was sampled after sunrise) and address the following questions: i) What are the main floral scent compounds emitted by the species? ii) Are the floral scent profiles similar to those described for other species pollinated by nocturnal bees? Floral scents were collected by dynamic headspace and analyzed by GC-MS (gas chromatography - mass spectrometry). The total amount of scent trapped ranged from 74 ng/flower/hour for Syzygium malaccense to 7556 ng/flower/hour for Eugenia dysenterica. A total of 46 floral scent compounds were detected in the samples with the most abundant compounds being the aromatics benzaldehyde, benzyl alcohol, 2-phenylethanol, methyl salicylate, 2-phenylethyl acetate, and benzyl acetate; the aliphatic compound 1-octanol; and the monoterpene linalool. The different species exhibited different relative scent patterns. Overall, the nocturnal scents of the studied species of Myrtaceae are dominated by aromatic compounds, which is in contrast to the scent profiles described for other plants pollinated by nocturnal bees.

Conflicting selection on floral scent emission in the orchid Gymnadenia conopsea.

Floral scent is a crucial trait for pollinator attraction. Yet only a handful of studies have estimated selection on scent in natural populations and no study has quantified the relative importance of pollinators and other agents of selection. In the fragrant orchid Gymnadenia conopsea, we used electroantennographic data to identify floral scent compounds detected by local pollinators and quantified pollinator-mediated selection on emission rates of 10 target compounds as well as on flowering start, visual display and spur length. Nocturnal pollinators contributed more to reproductive success than diurnal pollinators, but there was significant pollinator-mediated selection on both diurnal and nocturnal scent emission. Pollinators selected for increased emission of two compounds and reduced emission of two other compounds, none of which were major constituents of the total bouquet. In three cases, pollinator-mediated selection was opposed by nonpollinator-mediated selection, leading to weaker or no detectable net selection. Our study demonstrates that minor scent compounds can be targets of selection, that pollinators do not necessarily favour stronger scent signalling, and that some scent compounds are subject to conflicting selection from pollinators and other agents of selection. Hence, including floral scent traits into selection analysis is important for understanding the mechanisms behind floral evolution.

CYP79D73 Participates in Biosynthesis of Floral Scent Compound 2-Phenylethanol in Plumeria rubra.

Plumeria (Plumeria rubra), well known for its brightly colored and fragrant flowers, emits a number of floral volatile organic compounds (VOCs). Plumeria flowers emit a total of 43 VOCs including nine phenylpropanoids/benzenoids, such as 2-phenylethanol (2PE), benzaldehyde, 2-phenylacetaldehyde (PAld), (E/Z)-phenylacetaldoxime (PAOx), benzyl nitrile (BN), and 2-phenylnitroethane (PN). To identify genes and pathways involved in the production of the major compound 2PE, we analyzed the plumeria floral transcriptome and found a highly expressed, flower-specific gene encoding a cytochrome P450 family 79D protein (PrCYP79D73), which catalyzed the formation of (E/Z)-PAOx. Feeding experiments with deuterated phenylalanine or deuterated (E/Z)-PAOx showed that (E/Z)-PAOx is an intermediate in the biosynthesis of 2PE, as are two nitrogen-containing volatiles, BN and PN, in plumeria flowers. Crude enzyme extracts from plumeria flowers converted l-phenylalanine to (E/Z)-PAOx, PAld, 2PE, BN, and PN. The biosynthesis of these compounds increased with addition of PrCYP79D73-enriched microsomes but was blocked by pretreatment with 4-phenylimidazole, an inhibitor of cytochrome P450 enzymes. Moreover, overexpression of PrCYP79D73 in Nicotiana benthamiana resulted in the emission of (E/Z)-PAOx as well as PAld, 2PE, BN, and PN, all of which were also found among plumeria floral VOCs. Taken together, our results demonstrate that PrCYP79D73 is a crucial player in the biosynthesis of the major floral VOC 2PE and other nitrogen-containing volatiles. These volatiles may be required for plant defense as well as to attract pollinators for the successful reproduction of plumeria.

Multiplicity of human scent signature

BackgroundIn this paper, the term “human scent signature” refers to a group of chemical compounds in a human scent trace that are in certain relative concentrations that make an unambiguous identification of persons possible. At the present time, the scent identification of persons is performed using specially trained canines. However, the scent identification mechanism as well as the molecular composition of the human scent signature is entirely unrecognized. Delimitations of the group of chemical compounds according to their volatilities that specially trained canines use for the scent identification of persons were initially the main aim of this study.MethodsEleven volunteer scent samples were split into three groups of chemical compounds, i.e., into three disjointed scent fractions with different volatilities of the compounds via preparative gas chromatography. The human scent signatures were searched in these separated scent fractions using six specially trained canines (female German Shepherds).ResultsThe canines were able to identify individual persons successfully using different scent fractions. From this fact, it follows that one scent trace can contain more than only one group of scent compounds that can be used for scent identification by the trained canines. This observed phenomenon was named as “the multiplicity of the human scent signature” in this study. The scent identification line-up procedure provided the following results: The poorly volatile fraction resulted in an 85% success rate in the scent identification procedure. The middle fraction resulted in a 58% success rate, and the highly volatile fraction resulted in a 30% success rate.ConclusionsIn this study, it was found that the human scent sample contains more than one group of scent compounds; according to which the trained canines are able to identify human individuals. It means that the human scent sample contains more than only one scent signature. The authors of this research believe that results of this study will open a broad discussion about the multiplicity of the human scent signature, primary scent molecules, optimal canine training, and in general, the scent identification method in many countries.

Rose floral scent

The rose is the queen of flowers and is widely used as a garden plant and for the cut flower market. Roses are also used for the production of essential oil for the cosmetic and perfume industries. A lot of botanical roses are scented and use their volatiles to attract pollinators. Fragrances in garden roses are very diverse and scent has always been an important character in the selection process. Breeders have recently tried to introduce new fragrances, for instance reminiscent of fruit or spice odors. But despite their efforts, some roses on the market are not very fragrant, especially the ones selected for the cut flower market. The cause of this lack of scent is not known. In modern roses or Hybrid Tea roses, scent is mainly produced by petals, although stamens can also contribute to the emission of volatiles. Scent compounds are concentrated in rose petal epidermis, probably in small lipid droplets. In spite of numerous chemical studies, the biosynthetic pathways of many rose scent compounds are unknown. We are studying several genes involved in the biosynthesis of scent in rose. For example, we recently characterized the enzymes responsible for the so-called “tea scent” emitted by Chinese roses. Apart from “tea scent”, terpenoids, especially monoterpenes, are also major constituents of rose flowers, mostly responsible for the “typical rose scent”. Generally, terpenoid biosynthesis in plants is achieved by various terpene synthases. However, with a combination of transcriptomic and genetic approaches, our research group recently discovered a terpene synthase-independent pathway. A key enzyme of this pathway is RhNUDX1, belonging to the Nudix protein family. It has geranyl diphosphate diphosphohydrolase activity in vitro. A positive correlation was found between the expression levels of RhNUDX1 gene and the production of the monoterpene geraniol, indicating its essential role in scent production in roses.

Preliminary ecotoxicity assessment of selected flavour and fragrance compounds using Microtox assay

The bioluminescence inhibition bioassay using marine bacteria Vibrio fischeri is widely used as a tool to assess the toxicity of chemical compounds, because of the many benefits comprising cost and time effectiveness, rapidness, sensitivity, and ease of operation. In addition, the test is used for various types of organic and inorganic compounds. Due to the insolubility of organic compounds in water, a suitable solubilizer should be applied. The ecotoxicity of the solvent should be negligible in relation to marine bacteria. On account of superior human activities the synthesis of new chemical substances is inextricably linked to the emergence of chemical compounds that are a potential threat on environment. A Microtox system utilizing the 81.9% Basic Test with 14 dilutions was applied to pre-evaluate the ecotoxicity of β-cyclocitral oxime, citronellal oxime and perillaldehyde oxime. Substances solutions with an initial concentration of 0.036% in DMSO were prepared. The preliminary results show that the studied scent compounds are characterized by quite high toxicity. In order to confirm the received ecotoxicity values, it is necessary to carry out additional surveys using another range of concentrations and biotests on organisms at each trophic level.