4-pentenyl Isothiocyanate Research Articles

Glucosinolates with their Hydrolysis Products from Two Cruciferous Plants with Study of Antidiabetic Activity Based on Molecular Docking

Glucosinolates (Gls) are natural bioactive compounds that form metabolites called isothiocyanates (ITC) which have various therapeutic effects. This study aimed to isolate the glucosinolates of Carrichtera annua L.(DC) (CA) and Farsetia aegyptia Turra (FA) belonging to the Crucifereae family. Total Gls were isolated from the aqueous methanolic extract of the plants and further purified using an acidic aluminum oxide column. Some of the obtained Gls were identified via spectroscopic methods (UV, NMR, and MS) and the rest were hydrolyzed by myrosinase to the corresponding isothiocyanates (ITC) for identification by GC/MS. Only one Gls was identified in CA as 4-methylthio-3-butenyl Gls (MTBG) in addition to 6-methyl sulfonylhexyl isothiocyanates (ITC), while 6-methyl sulfonyl-6-hydroxy hexyl ITC, 4-pentenyl ITC, 3-methylthio propyl ITC, 5-hydroxy pentyl ITC and 4-methylsulphinyl butyl ITC were identified in FA. The Gls demonstrated high binding activity to α-glucosidase and amylase, good pharmacokinetic characteristics, and exerted no carcinogenetic effects.

Influence of Genotype on High Glucosinolate Synthesis Lines of Brassica rapa.

This study was conducted to investigate doubled haploid (DH) lines produced between high GSL (HGSL) Brassica rapa ssp. trilocularis (yellow sarson) and low GSL (LGSL) B. rapa ssp. chinensis (pak choi) parents. In total, 161 DH lines were generated. GSL content of HGSL DH lines ranged from 44.12 to 57.04 μmol·g−1·dry weight (dw), which is within the level of high GSL B. rapa ssp. trilocularis (47.46 to 59.56 μmol g−1 dw). We resequenced five of the HGSL DH lines and three of the LGSL DH lines. Recombination blocks were formed between the parental and DH lines with 108,328 single-nucleotide polymorphisms in all chromosomes. In the measured GSL, gluconapin occurred as the major substrate in HGSL DH lines. Among the HGSL DH lines, BrYSP_DH005 had glucoraphanin levels approximately 12-fold higher than those of the HGSL mother plant. The hydrolysis capacity of GSL was analyzed in HGSL DH lines with a Korean pak choi cultivar as a control. Bioactive compounds, such as 3-butenyl isothiocyanate, 4-pentenyl isothiocyanate, 2-phenethyl isothiocyanate, and sulforaphane, were present in the HGSL DH lines at 3-fold to 6.3-fold higher levels compared to the commercial cultivar. The selected HGSL DH lines, resequencing data, and SNP identification were utilized for genome-assisted selection to develop elite GSL-enriched cultivars and the industrial production of potential anti-cancerous metabolites such as gluconapin and glucoraphanin.

Small Functional Foods: Comparative Phytochemical and Nutritional Analyses of Five Microgreens of the Brassicaceae Family.

Microgreens are the seedlings of herbs and vegetables which are harvested at the development stage of their two cotyledonary leaves, or sometimes at the emergence of their rudimentary first pair of true leaves. They are functional foods, the consumption of which is steadily increasing due to their high nutritional value. The species of the Brassicaceae family are good sources of bioactive compounds, with a favorable nutritional profile. The present study analyzed some phytochemical compounds with nutritional values, such as chlorophylls, polyphenols, carotenoids, anthocyanins, ascorbic acid, total and reducing sugars, and the antioxidant activity of five Brassicaceae species: broccoli (Brassica oleracea L.), daikon (Raphanus raphanistrum subsp. sativus (L.) Domin), mustard (Brassica juncea (L.) Czern.), rocket salad (Eruca vesicaria (L.) Cav.), and watercress (Nasturtium officinale R.Br.). Broccoli had the highest polyphenol, carotenoid and chlorophyll contents, as well as a good antioxidant ability. Mustard was characterized by high ascorbic acid and total sugar contents. By contrast, rocket salad exhibited the lowest antioxidant content and activity. The essential oil (EO) composition of all of these species was determined in order to identify their profile and isothiocyanates content, which are compounds with many reported health benefits. Isothiocyanates were the most abundant group in broccoli (4-pentenyl isothiocyanate), mustard (allyl isothiocyanate), and watercress (benzyl isothiocyanate) EOs, while rocket salad and daikon exhibited higher contents of monoterpene hydrocarbons (myrcene) and oxygenated diterpenes (phytol), respectively. Broccoli microgreens exhibited the overall best nutritional profile, appearing as the most promising species to be consumed as a functional food among those analyzed.

The Molecular Basis of Host Selection in a Crucifer-Specialized Moth

Glucosinolates (GSs) are sulfur-containing secondary metabolites characteristic of cruciferous plants [1, 2]. Their breakdown products, isothiocyanates (ITCs), are released following tissue disruption by insect feeding or other mechanical damages [3, 4]. ITCs repel and are toxic to generalist herbivores, while specialist herbivores utilize the volatile ITCs as key signals for localizing host plants [5, 6]. However, the molecular mechanisms underlying detection of ITCs remain open. Here, we report that in the diamondback moth Plutella xylostella, a crucifer specialist, ITCs indeed drive the host preference for Arabidopsis thaliana, and the two olfactory receptors Or35 and Or49 are essential for this behavior. By performing gene expression analyses, we identified 12 (out of 59 in total) female-biased Ors, suggesting their possible involvement in oviposition choice. By ectopically expressing these Ors in Xenopus oocytes and screening their responses with 49 odors (including 13 ITCs, 25 general plant volatiles, and 11 sex pheromone components), we found that Or35 and Or49 responded specifically to three ITCs (iberverin, 4-pentenyl ITC, and phenylethyl ITC). The same ITCs also exhibited highest activity in electroantennogram recordings with female antennae and were the strongest oviposition stimulants. Knocking out either Or35 or Or49 via CRISPR-Cas9 resulted in a reduced oviposition preference for the ITCs, while double Or knockout females lost their ITC preference completely and were unable to choose between wild-type A.thaliana and a conspecific ITC knockout plant. We hence conclude that the ITC-based oviposition preference of the diamondback moth for its host A.thaliana is governed by the cooperation of two highly specific olfactory receptors.

Disruption of host-seeking behaviour by the salmon louse, Lepeophtheirus salmonis, using botanically derived repellents.

The potential for developing botanically derived natural products as novel feed-through repellents for disrupting settlement of the salmon louse, Lepeophtheirus salmonis (Caligidae) upon farmed Atlantic salmon, Salmo salar, was investigated using an established laboratory vertical Y-tube behavioural bioassay for assessing copepodid behaviour. Responses to artificial sea water conditioned with the odour of salmon, or to the known salmon-derived kairomone component, α-isophorone, in admixture with selected botanical materials previously known to interfere with invertebrate arthropod host location were recorded. Materials included oils extracted from garlic, Allium sativum (Amaryllidaceae), rosemary, Rosmarinus officinalis (Lamiaceae), lavender, Lavandula angustifolia (Lamiaceae), and bog myrtle, Myrica gale (Myricaceae), and individual components (diallyl sulphide and diallyl disulphide from garlic; allyl, propyl, butyl, 4-pentenyl and 2-phenylethyl isothiocyanate from plants in the Brassica genus). Removal of attraction to salmon-conditioned water (SCW) or α-isophorone was observed when listed materials were presented at extremely low parts per trillion (ppt), that is picograms per litre or 10-12 level. Significant masking of attraction to SCW was observed at a level of 10ppt for diallyl disulphide and diallyl sulphide, and allyl isothiocyanate and butyl isothiocyanate. The potential of very low concentrations of masking compounds to disrupt Le.salmonis copepodid settlement on a host fish has been demonstrated invitro.

Determination of the absolute configuration of a novel odour-active lactone,cis-3-methyl-4-decanolide, in wasabi (Wasabia japonicaMatsum.)

The aroma of freshly grated wasabi (Wasabia japonica Matsum.) is not only pungent but also sweet, fruity, green and creamy. In this study we investigated wasabi aroma concentrate by aroma extract dilution analysis. Ten odorants were detected as odour-active compounds at the highest flavour dilution factors of 256 and 1024: 3-methyl-2-butene-1-thiol, allyl isothiocyanate, (Z)-1,5-octadien-3-one, 2-isopropyl-3-methoxypyrazine, 4-pentenyl isothiocyanate, 5-hexenyl isothiocyanate, 3-methyl-2,4-nonanedione, cis-3-methyl-4-decanolide, 6-(methylthio)hexyl isothiocyanate, and vanillin. Among them, (Z)-1,5-octadien-3-one and cis-3-methyl-4-decanolide were identified for the first time in wasabi. To determine the absolute stereochemistry of cis-3-methyl-4-decanolide in wasabi, we synthesized the stereoisomers of 3-methyl-4-decanolide from optically active γ-decalactone. Finally, the absolute configurations of cis-3-methyl-4-decanolide were determined as (3R,4R)-3-methyl-4-decanolide by matching the retention time and odour qualities in chiral GC-MS. Copyright © 2014 John Wiley & Sons, Ltd.

Inhibitory Effects of Wasabi Isothiocyanates on Chemical Mediator Release in RBL-2H3 Rat Basophilic Leukemia Cells

Wasabi is a plant of Japanese origin. It belongs to the family Brassicaceae and produces various isothiocyanates (ITCs). To clarify the type I allergies inhibited by wasabi ITCs, we investigated the inhibitory effect on chemical mediator release from dinitrophenylated bovine serum albumin (DNP-BSA)-stimulated RBL-2H3 rat basophilic leukemia cells. Allyl ITC (AITC), sec-butyl ITC (s-BuITC), and 3-butenyl ITC (3-BuITC), which have 3 or 4 carbon chains, inhibited histamine release but did not inhibit the release of leukotriene B4 (LTB4) or cysteinyl LTs (CysLTs). 4-Pentenyl ITC (4-PeITC) and 5-hexenyl ITC (5-HeITC), which have 5 or 6 carbon chains and an unsaturated bond at the end, inhibited LTB4 release but did not inhibit the release of histamine or CysLTs. 6-Methylthiohexyl ITC (6-MTITC), 6-methylsulfinylhexyl ITC (6-MSITC), and 6-methylsulfonylhexyl ITC (6-MSFITC), which have a sulfur atom inserted at the end of a 6-carbon chain, inhibited the release of histamine, LTB4, and CysLTs and the elevation in intracellular Ca(2+). These results suggest that wasabi ITCs inhibited type I allergies by inhibiting chemical mediator release and that the inhibitory effects on each chemical mediator were due to differences in the side chain structure of the wasabi ITCs.

Male Phyllotreta striolata (F.) Produce an Aggregation Pheromone: Identification of Male-specific compounds and Interaction with Host Plant Volatiles

The chrysomelid beetle Phyllotreta striolata is an important pest of Brassicaceae in Southeast Asia and North America. Here, we identified the aggregation pheromone of a population of P. striolata from Taiwan, and host plant volatiles that interact with the pheromone. Volatiles emitted by feeding male P. striolata attracted males and females in the field. Headspace volatile analyses revealed that six sesquiterpenes were emitted specifically by feeding males. Only one of these, however, elicited an electrophysiological response from antennae of both sexes. A number of host plant volatiles, e.g., 1-hexanol, (Z)-3-hexen-1-ol, and the glucosinolate hydrolysis products allyl isothiocyanate (AITC), 3-butenyl isothiocyanate, and 4-pentenyl isothiocyanate also elicited clear responses from the antenna. The active male-specific compound was identified as (+)-(6R,7S)-himachala-9,11-diene by chiral stationary phase gas-chromatography with coupled mass spectrometry, and by comparison with reference samples from Abies nordmanniana, which is known to produce the corresponding enantiomer. The pheromone compound was synthesized starting from (-)-α-himachalene isolated from Cedrus atlantica. Under field conditions, the activity of the synthetic pheromone required concomitant presence of the host plant volatile allyl isothiocyanate. However, both synthetic (+)-(6R,7S)-himachala-9,11-diene alone and in combination with AITC were attractive in a two-choice laboratory assay devoid of other natural olfactory stimuli. We hypothesize that P. striolata adults respond to the pheromone only if specific host volatiles are present. In the same laboratory set up, more beetles were attracted by feeding males than by the synthetic stimuli. Thus, further research will be necessary to reveal the components of a more complex blend of host or male-produced semiochemicals that might enhance trap attractiveness in the field.

Evaluation of Antibacterial Activity of 3‐Butenyl, 4‐Pentenyl, 2‐Phenylethyl, and Benzyl Isothiocyanate in Brassica Vegetables

This study investigated antibacterial activities of 4 isothiocyanates (3-butenyl, 4-phentenyl, 2-phenylethyl, and benzyl isothiocyanate) against 4 Gram-positive bacteria (Bacillus cereus, Bacillus subtilis, Listeria monocytogenes, and Staphylococcus aureus) and 7 Gram-negative bacteria (Aeromonas hydrophila, Pseudomonas aeruginosa, Salmonella choleaesuis, Salmonella enterica, Serratia marcescens, Shigella sonnei, and Vibrio parahaemolyticus) by an agar disc diffusion assay. Benzyl isothiocyanate (> 90.00 mm inhibition zone diameter at 0.1 μL/mL) and 2-phenylethyl isothiocyanate (58.33 mm at 0.2 μL/mL) showed large inhibition zones especially against B. cereus. Also, 3-butenyl isothiocyanate (21.67 mm at 1.0 μL/mL) and 4-pentenyl isothiocyanate (19.67 mm at 1.0 μL/mL) displayed potent antibacterial activity against A. hydrophila. Benzyl and 2-phenylethyl isothiocyanate indicated higher activity against most of the pathogenic bacteria than 3-butenyl and 4-pentenyl isothiocyanate, and were more effective against Gram-positive bacteria than Gram-negative bacteria.

Hexane Extract of Raphanus sativus L. Roots Inhibits Cell Proliferation and Induces Apoptosis in Human Cancer Cells by Modulating Genes Related to Apoptotic Pathway

Raphanus sativus, a common cruciferous vegetable has been attributed to possess a number of pharmacological and therapeutic properties. It has been used in indigenous system of medicine for the treatment of various human ailments in India. This present study evaluated the chemopreventive efficacy of different parts of R. sativus such as root, stem and leaves, extracted with solvents of varying polarity and investigated the molecular mechanism leading to growth arrest and apoptotic cell death in human cancer cell lines. Of the different parts, significant growth inhibitory effect was observed with hexane extract of R. sativus root. Analysis of hexane extract by GC-MS revealed the presence of several isothiocyanates (ITCs) such as 4-(methylthio)-3-butenyl isothiocyanate (MTBITC), 4-(methylthio)-3-butyl isothiocyanate (erucin), 4-methylpentyl isothiocyanate, 4-pentenyl isothiocyanate and sulforaphene. R. sativus root extract induced cell death both in p53 proficient and p53 deficient cell lines through induction of apoptotic signaling pathway regardless of the p53 status of cells. The molecular mechanisms underlying R. sativus-induced apoptosis may involve interactions among Bcl(2) family genes, as evidenced by up-regulation of pro-apoptotic genes and down-regulation of anti-apoptotic genes along with activation of Caspase-3. Our findings present the first evidence that hexane extract of R. sativus root exerts potential chemopreventive efficacy and induces apoptosis in cancer cell lines through modulation of genes involved in apoptotic signaling pathway.

Volatile Constituents of the Tuberous Tap-root, Leaf and Seed of Brassica rapa L. ssp. rapa Cultivated in Isfahan (Iran)

Volatile constituents of the dried tuberous tap-root, leaf and seed of cultivated Brassica rapa L. ssp. rapa collected after hydrolysis were analyzed by GC and GC/MS. The major volatile constituents of the root were 2-phenylethyl isothiocyanate (32.6%), sec-butyl isothiocyanate (25.7%), 4-pentenyl isothiocyanate (12.8%), 5-methylthiopentyl isothiocyanate (10.0%) and 2-hexenal (4.6%), while the major volatile components of the leaf oil were 4-pentenyl isothiocyanate (53.7%), sec-butyl isothiocyanate (24.3%) and 3-butenyl isothiocyanate (15.8%). The main volatile constituents of the seed were 3-butenyl isothiocyanate (59.7%), 4-pentenyl isothiocyanate (31.0%) and sec-butyl isothiocyanate (1.7%).

Glucosinolates, glycosidically bound volatiles and antimicrobial activity of Aurinia sinuata (Brassicaceae)

Volatiles of Aurinia sinuata (L.) Griseb. were isolated from aerial parts and analysed by gas chromatography/gas chromatography–mass spectrometry (GC/GC–MS). The main compounds were glucosinolate degradation products originating from glucoberteroin, glucobrassicanapin and glucoalyssin. They were: 6-(methylthio)hexanenitrile (1.8–51.5%), 6-(methylsulfinyl)hexanenitrile (0–11.5%), 5-(methylsulfinyl)pentyl isothiocyanate (0–10.2%), 5-(methylthio)pentyl isothiocyanate (0.4–9.5%), 4-pentenyl isothiocyanate (0.7–8.9%), 5-hexenenitrile (2.6–14.6%) and 5,6-epithiohexanenitrile (0–3.4%). Also other volatiles were identified, such as fatty acids and esters (0.3–19.2%), phenols, phenylpropane derivatives and related compounds (0.4–15.8%), aliphatic alcohols and carbonyl compounds (4.2–11.6%) and some other compounds in smaller percentages. The O-glycosidically bound volatiles were isolated from aerial parts of A. sinuata. After the enzymatic hydrolysis and GC and GC–MS analyses, among 20 volatile aglycones identified, eugenol (73.0%) was the main one. The volatile samples containing glucosinolate degradation products were evaluated for antimicrobial activity using the disc diffusion method with calculated minimum inhibitory concentrations (MIC). All volatile samples expressed a wide range of growth inhibition activity against both Gram-positive and Gram-negative bacteria and fungi. The minimum inhibitory concentrations varied between 0.008 and 0.115 mg/ml.

Anticancer and Antimicrobial Activities of .BETA.-Phenylethyl Isothiocyanate in Brassica rapa L.

Glucosinolates, precursors of isothiocyanates, are present in cruciferous vegetables such as the turnip (Brassica rapa L.). Glucosinolates are usually broken down through hydrolysis catalyzed by myrosinase released from damaged plant cells. Glucosinolates and their breakdown products, in particular isothiocyanates, have long been known to have various pharmaceutical benefits, including anticarcinogenic, antimicrobial and antioxidant properties. In this study, quantitative analyses of isothiocyanates and total glucosinolates in turnip, which was divided into three parts, were performed by UV-spectrometer, GC and GC/MS. Total glucosinolates showed no significant differences among different parts of turnip. However, the amounts of 3-butenyl and 4-pentenyl isothiocyanates in turnip leaf were higher than those in other parts. β-Phenylethyl isothiocyanate, abundant in the peel, showed the highest content in turnip. In addition, β-Phenylethyl isothiocyanate inhibited the growth of human-derived hepatoma cell line (HepG2) in a concentration-dependent manner (IC50 value of 24.5 μM), assessed by the MTT method. β-Phenylethyl isothiocyanate also exhibited antimicrobial activity against food-borne pathogens Vibrio parahaemolyticus, Staphylococcus aureus and Bacillus cereus. In particular, minimum inhibitory concentration (MIC) against Vibrio parahaemolyticus was the most efficient, at 100 μg/ml. These results suggest that the major isothiocyanate in turnip is β-phenylethyl isothiocyanate. Furthermore, β-phenylethyl isothiocyanate may have anticancer effects and antimicrobial properties against food-borne pathogens.

Leaching of isothiocyanates through intact soil following simulated biofumigation

Biofumigation can be used as an alternative to conventional soil fumigation to control soil-borne pests. With biofumigation, plant tissue with a natural content of glucosinolates (cruciferous plants) is damaged and incorporated into the topsoil. When the plant tissue is damaged, the glucosinolates come into contact with the endogenous enzyme myrosinase, which catalyse the hydrolysis of glucosinolates into various products depending on the reaction conditions. Isothiocyanates are among the potential products formed from these reactions. We investigated if the isothiocyanates from rape plant material were leached through the soil to drain depth when a heavy rainstorm followed the biofumigation. We applied isothiocyanates from rape plant material (1,480 μmol m−2) to four large (0.6 m diameter, 1.0 m long) intact soil monoliths from a loamy and a sandy soil and conducted a leaching experiment under semi-field conditions. The soil monoliths were irrigated with 70–90 mm (10 mm h−1) and the concentrations of three isothiocyanates (3-butenyl, 4-pentenyl and 2-phenethyl) were monitored in the leachate. Between 0 and 14.8 mmol isothiocyanates were leached for each mol of isothiocyanates applied during application of 70–90 mm irrigation. The distribution coefficient estimated from leached concentrations was 0.04–1.19 for 3-butenyl, 0.04–1.15 for 4-pentenyl isothiocyanate and 0.037–0.97 for 2-phenethyl isothiocyanate. The concentration of total isothiocyanates in the leachate was in the same order of magnitude as the LD50 of isothiocyanates for sensitive aquatic organisms.

Volatile components of the leaves ofBrassica rapa L. var.perviridis Bailey

The chemical composition of the essential oils from the leaves of Brassica rapa Linn. var. perviridis Bailey has been investigated by GC and GC–MS. The leaf essential oil was found to contain 48 volatile components, representing 94.0–96.6% of the oil, which were characterized. The main constituents were 3-butenylisothiocyanate (1.4–29.2%), 4-pentenyl isothiocyanate (8.2–23.5%), 2-methyl 5-hexenenitrile (1.3–16.8%), 2-phenylethyl isothiocyanate (7.0–13.7%) and phytol (6.1–23.5%). The essential oil from the leaves of B. rapa was characterized by a high content of sulphur- and nitrogen-containing compounds. Copyright © 2004 John Wiley & Sons, Ltd.

Assessment of Sinapis alba, Brassica napus and S. alba×B. napus hybrids for resistance to cabbage seedpod weevil, Ceutorhynchus assimilis (Coleoptera: Curculionidae)

Canola (Brassica napus L.), yellow mustard (Sinapis alba L.) and intergeneric crosses of S. alba×B. napus were assessed for resistance (antixenosis) to the cabbage seedpod weevil (Ceutorhynchus assimilis Paykull). Pod trichomes did not appear to be a major factor in the resistance of S. alba to weevils. The number of feeding punctures and eggs per pod in S. alba was not significantly different in pods with trichomes than in those where the trichomes had been removed. Choice and no-choice laboratory tests examining feeding punctures and eggs laid per pod suggested that resistance in S. alba is not conferred in the intergeneric cross, S. alba×B. napus. Similar data on feeding and weevil oviposition were found in field test plots. However, despite many eggs being laid in S. alba×B. napus hybrid plants, fewer cabbage seedpod weevil larvae developed to exit the intergeneric hybrid pods. Glucosinolate analyses of leaves, pods and seeds showed that S. alba plants have a high concentration of p-hydroxybenzyl glucosinolate in all three plant parts, but B. napus has no p-hydroxybenzyl. Interestingly the intergeneric hybrid examined in this study had 62% and 60% of p-hydroxybenzyl concentration in the leaves and seeds, respectively, than was found in the S. alba parent. However, pod tissues contained very little (3%) compared with the S. alba parent. It is possible, therefore, that the adult cabbage seedpod weevil feeds on the pods of the intergeneric hybrid and lays eggs in the pod, because of the low concentration of p-hydroxybenzyl glucosinolate, but the larvae then fail to develop as they feed on the seeds containing high concentrations of p-hydroxybenzyl glucosinolate. It should be noted also that this hybrid produced pods that were more similar in physical shape to canola pods and that this may also be a factor determining cabbage seedpod weevil feeding and subsequent egg laying. In addition, both B. napus and the intergeneric hybrid produced 3-butenyl and 4-pentenyl glucosinolates in their pods, and degradation products (3-butenyl, and 4-pentenyl isothiocyanates) from these glucosinolate types, are known to be stimulatory kairomones that attract cabbage seedpod weevil. Further studies are being conducted to examine these factors in more detail.

Effect of Visual Cues and a Mixture of Isothiocyanates on Trap Capture of Cabbage Seed Weevil, Ceutorhynchus assimilis

The effect of trap design, trap color, and a mixture of isothiocyanates on the capture of Ceutorhynchus assimilis (Paykull) was studied in a series of field experiments. Unbaited yellow water traps, a yellow sticky box trap, and a yellow sticky card trap, mounted vertically, or at 45° to the vertical with the yellow card facing upwards were effective for capturing seed weevils, but a horizontal yellow sticky card trap caught few. White, green, and black traps were unattractive. During migratory periods, trap catch could be enhanced two to four times with a lure consisting of a mixture of allyl, 3-butenyl, 4-pentenyl, and 2-phenylethyl isothiocyanates, but this bait did not attract in a trap with ineffective design. The sticky card trap, mounted at 45° to the vertical and baited with the isothiocyanate mixture, may be useful for monitoring movement of C. assimilis during migratory periods. However, during the colonization phase, lures of either a mixture of isothiocyanates or of allyl isothiocyanate alone were not attractive.

The Potential of Semiochemicals for Control ofPhorodon humuli(Homoptera: Aphididae)

Field experiments employing yellow water-traps with vials releasing methyl salicylate, butyl isothiocyanate, 4-pentenyl isothiocyanate and diethyltoluamide were conducted during the spring migration of Phorodon humuli (Schrank), with the aim of identifying substances which might be used in the field to deter landing on hop plants. Methyl salicylate and the two isothiocyanates reduced trap catches of P. humuli. During the spring of 1994 a slow-release formulation of methyl salicylate and a beta-acid-rich hop resin sprayed on to hop plants did not reduce aphid infestations significantly. In autumn cis,cis-nepetalactol the main component of P. humuli's sex pheromone, prepared by various synthetic routes, increased trap catches of males and gynoparae equally. Catches of males in pheromone traps situated in a hop garden decreased with increasing trap height. Catches of males in traps charged with increasing doses of the cis,cis-nepetalactol peaked at 1 mg and then plateaued, whereas catches of gynoparae peaked similarly at 1 mg and then decreased. The effects of kairomones from an extract of the primary host, sex pheromone and a visual cue from yellow compared with clear water-traps were additive. The prospects for developing a semiochemicals-based control strategy against P. humuli, using some or all of the above elements, are discussed.

Release of alkenyl isothiocyanates and other volatiles from Brassica rapa seedlings during infection by Alternaria brassicae

When Brassica rapa seedlings were inoculated with the fungal pathogen Alternaria brassicae, 3-butenyl and 4-pentenyl isothiocyanates were released, together with dimethyl disulphide, dimethyl trisulphide, 4-oxoisophorone and a number of sesquiterpenes. Release of isothiocyanates is evidence for the catabolism of glucosinolates during infection, which is a prerequisite for their involvement in resistance.

Behavioral and electrophysiological responses of Aphids to host and nonhost plant volatiles

Alate and apterous virginoparae ofAphis fabae Scop, and alate virginoparae ofBrevicoryne brassicae (L.), walking in a linear track olfactometer, were attracted by odor from leaves of their host plants.A. fabae responded to odor from undamaged but not damaged bean leaves. Gynoparae (autumn migrants) ofA. fabae, however, did not respond to their host plant (spindle,Euonymus europaeus) odor. Odors of certain nonhost plants masked the attractiveness of the host plant leaves, but tansy (Tanacetum vulgare) and summer savory (Satureja hortensis) volatiles repelledB. brassicae andA. fabae, respectively. 3-Butenyl isothiocyanate attractedB. brassicae andLipaphis erysimi (Kalt.), the latter species being more sensitive in both behavioral and electrophysiological studies. Isothiocyanate receptors were found on the antennae ofA. fabae, which was repelled by these compounds, 4-pentenyl isothiocyanate being the most active.