Defensive steroids from a carrion beetle (Silpha novaboracensis)

Two novel steroids, 3,7-dihydroxy-14-pregn-4-en-15,20-dione (1) and 3,7, 20-trihydroxy-14-pregn-4-en-15-one (4), have been characterized from the rectal gland ofSilpha novaboracensis (Coleoptera: Silphidae). Judging from the function of comparable pregnanes in another species ofSilpha, the compounds may play an antipredator role.Paper No. 81 of the seriesDefense Mechanisms of Arthropods. Paper No. 80 is Eisner, T., Deyrup, M., Jacobs, R., and Meinwald, J.,J. Chem. Ecol. 12:1407–1415.     

Seasonal variation of lipids in femoral gland secretions of male green iguanas (Iguana iguana)

Femoral gland secretions were collected from 21 captive adult male green iguanas (Iguana iguana) in Orotina, Costa Rica, and San Diego, California, during the breeding (November) and nonbreeding (March) seasons. Lipids were extracted with methylene chloride, weighed, separated by thin-layer chromatography, and analyzed by gas chromatography-mass spectrometry. Free and esterified C₁₄-C₂₆ fatty acids, 5-cholestan-3-ol (epico-prostanol), cholest-5-en-3-ol (cholesterol), cholest-5-en-24-methyl-3-ol (campesterol), cholesta-5,22-dien-24b-ethyl-3-ol (stigmasterol), cholesta-8,24(5)-dien-4,4,14-trimethyl-3-ol (lanosterol), cholest-5-en-24-ethyl-3-ol (-sitosterol), and two uncharacterized sterols were indicated. More lipids were recovered from femoral gland secretions obtained during the breeding than the nonbreeding months, indicating that secretion deposits may be more detectable during the mating season.     

Investigation of the role of diterpenes produced by marine pulmonatesTrimusculus reticulatus andT. conica

The intertidal pulmonate limpetTrimusculus reticulatus, which is found in caves or crevices along the California coast, was previously reported to contain two novel diterpenoids, 6-isovaleroxylabda-8,13-dien-7,15-diol (1) and 2,7-diacetoxy-6-isovaleroxylabda-8,13-dien-15-ol (2). Dissection of the animals prior to extraction revealed that the diterpenoids were concentrated in the mantle, foot, and mucus, but not in the viscera. The presence ofT. reticulatus or its mucus was toxic to veliger larvae of the sabellariid reef-building tube wormPhragmatopoma californica. The major diterpenoid1 was responsible for the observed larvicidal activity. Protection against overgrowth by settling invertebrate larvae is important for the survival of this sessile filter-feeding pulmonate. A related pulmonate,T. conica, which was found in similar intertidal habitats in New Zealand, contained 6-acetoxy-7-isovaleroxylabda-8,13-dien-15-oic acid (3) and 1,7,12,18-tetraacetoxy-cholest-5-en-3-ol (4). The diterpene3 was also localized in the foot, mantle, and mucus ofT. conica but was not larvicidal toP. californica.     

Electroantennogram response of alfalfa seed chalcid,Bruchophagus roddi (Hymenoptera: Eurytomidae) to host- and nonhost-plant volatiles

The alfalfa seed chalcid (ASC),Bruchophagus roddi, is a monophagous pest of alfalfa that parasitizes developing seeds. To further understand the olfactory basis of host-plant recognition by ASCs, we recorded electroantennograms (EAGs) from females and males to 39 volatiles from both alfalfa and red clover. The chemoreceptive sensitivity of ASCs was selective for certain general classes of compounds, defined by their carbon-chain length (C₆ and C₈), structure (aliphatics and phenolics), isomerism, and/or functional group (acetates, ketones, and alcohols). The compounds that elicited the largest EAGs were ranked as follows: (Z)-3-hexenyl acetate > hexyl acetate acetophenone octan-3-one methyl salicylate > octan-3-ol > oct-1-en-3-one > oct-1-en-3-ol (E)--ocimene (Z)- and (E)-3-hexen-1-ols. Over half the test compounds elicited significantly different responses between the sexes, and female antennal responses exceeded those of males for twice the number of these volatiles. Relationships of the tested volatiles to host-plant composition, EAG responses, and ASC behaviors showed no consistent correlations. However, nearly all of the host-plant volatiles known to stimulate behavioral activity also elicited moderate to potent EAG responses.     

Isolation and identification of cotton synomones mediating searching behavior by parasitoidCampoletis sonorensis

In laboratory bioassays, the parasitoidCampoletis sonorensis was attracted to the following sesquiterpenes isolated from cotton essential oil: -humulene, -bisabolene, -caryophyllene oxide, spathulenol, -bisabolol, and a new, naturally occurring bisabolene-related alcohol, (2-p-tolyl-6-methylhept-5-en-2-ol) which we name gossonorol. This is the first report of spathulenol in cotton. -Caryophyllene, a major component of cotton, was not attractive to the parasitoids. The response of the parasitoids to these compounds and the possibility of augmenting parasitoid activity in the field by manipulating plant secondary metabolites is discussed.Synomone: A chemical produced or acquired by an organism that benefits both the emitting and receiving organisms (Nordlund and Lewis, 1976).     

New sesquiterpenes fromMaytenus species (Celastraceae). Taxonomic and chemotaxonomic considerations concerning chileanMaytenus

Three new dihydro--agarofuran sesquiterpenes from two species ofMaytenus were isolated and their structures were elucidated by means of¹H and¹³C NMR studies. The differences and similarities noted in the chemical content of the dihydro--agarofuran sesquiterpenes from the fourMaytenus species from Chile are in line with the taxonomic characterization of these species; their geographical distribution is also given.     

β-Phellandrene: kairomone for pine engraver,Ips pini (Say) (Coleoptera: Scolytidae)

The responses ofIps pini (Scolytidae) to multiple-funnel traps baited with the pheromone, ipsdienol, and various monoterpenes were determined in stands of lodgepole pine in southern and central British Columbia.Ips pini was attracted to both ipsdienol and -phellandrene, demonstrating that -phellandrene is a kairomone for this species.Lasconotus complex (Colydiidae) and aCorticeus sp. (Tenebrionidae) were attracted to both ipsdienol and -phellandrene. TheCorticeus sp. exhibited a synergistic response to the combination of ipsdienol and -phellandrene; the responses of the other two species to the combination were additive. The predators,Thanasimus undatulus, Enoclerus sphegeus, andE. lecontei (Cleridae), were attracted to ipsdienol-baited traps, whileMonochamus clamator (Cerambycidae) andDendroctonus ponderosae (Scolytidae) were attracted to -phellandrene. Attraction of all eight species increased with increasing release rates of ipsdienol and/or -phellandrene.     

Bioactive Steroids and Triterpenes from Melilotus messanensis and Their Allelopathic Potential

The aerial parts of Melilotus messanensis (sweet clover) afforded, from moderately and polar bioactive fractions, 11 triterpenes and five steroids. A series of aqueous solutions at 10^–4–10^–9 M of five steroids and nine triterpenes was monitored to test their effects on germination and growth of the monocots Hordeum vulgare and Allium cepa, and the dicots Lactuca sativa (var. nigra and var. romana) and Lycopersicon esculentum. An important stimulatory effect on H. vulgare germination (between 40% and 80% for almost all tested compounds) was observed. Some considerations about the ecological role of triterpenes on M. messanensis are made. In addition to known lupane triterpenes (platanic acid and 3,28,30-lup-20(29)-enetriol), oleanane triterpenes (soyasapogenol B, soyasapogenol G, and messagenolide), a gammacerane triterpene (gammacer-16-en-3-one), five new lupane triterpenes (messagenic acids A–E: (27-cis-4-hydroxycinnamoyloxy)-betulinic acid; 27-(trans-4-hydroxycinnamoyloxy)betulinic acid; 20(S)-3-hydroxy-29-oxolupan-28-oic acid; 3,30-dihydroxylup-20(29)-en-28-oic acid; and 3,20-dihydroxylup-18(19)-en-28-oic acid, respectively), and sterols (-sitosterol, ergosterol peroxide, 7-hydroxysitosterol, 7-hydroxysitosterol, and 7-oxositosterol) were isolated and chemically characterized. Their structures and stereochemistry were elucidated by spectroscopic methods (one- and two-dimensional ¹H and ¹³C NMR, IR, MS).     

Catalytic Combustion of Model Carbon Particles (CPs) over Pt/β-SiC Catalyst

Platinum catalyst supported on a medium surface area -SiC was successfully used for the catalytic combustion of model carbon particles and compared to a catalyst supported on a low surface area -SiC. The -SiC-based catalyst showed no deactivation as a function of cycling tests while a strong deactivation was observed on the -SiC-based catalyst. This deactivation was attributed to the progressive encapsulation of the platinum particles by a layer of silica which built up during the combustion cycle. These results render possible the use of Pt/-SiC catalyst as a diesel carbon particle catalytic filter with continuous regeneration.     

Variation in aphid alarm pheromone content among glandular and eglandular-hairedMedicago accessions

Pea (Acyrthosiphon pisum Harris) and blue alfalfa aphid (A. kondoi Shinji) deterrency in alfalfa (Medicago saliva L.) may result from incorporating higher levels of the aphid alarm pheromone,(E)--farnesene relative to(E)--caryophyllene. We evaluated five eglandular and two glandular-haired alfalfa accessions for differences in(E)--farnesene and(E)--caryophyllene content under glasshouse conditions using supercritical fluid extraction and gas chromatography. In addition, pea and blue alfalfa aphid olfactory behavioral tests were conducted uponMedicago species containing different ratios of(E)--famesene relative to(E)--caryophyllene. No differences in(E)--caryophyllene content were observed among the seven entries (=0.42 ng/g plant material). Significant differences (P 0.05) among entries were observed for(E)--famesene content, with KS94GH6 exhibiting the highest (1.18 ng/g), and CUF 101 the lowest levels (0.35 ng/g). Elite tetraploid sources possessed significantly lower levels (=0.42 ng/g) of(E)--farnesene than did wild and cultivated diploid accessions (=0.83 ng/g). Olfactory behavioral tests for both the pea and blue alfalfa aphids demonstrated KS94GH6 repelled aphids while cultivated alfalfa types attracted aphids in each case. Previously demonstrated aphid resistance in diploid KS94GH6 may result from superior(E)-- farnesene levels, but(E)--farnesene is probably not a factor in cultivated alfalfa resistance. Finally, accession KS94GH6 could act as an excellent germplasm resource for the incorporation of higher(E)--farnesene levels into cultivated alfalfa.Research supported by the New Mexico State University Agricultural Experiment Station.     

Fundamental aspects and potential roles of ecdysteroids in schistosomes an update overview

The human digenic trematodeSchistosoma mansoni produces ecdysteroid hormones. Both ecdysone (22R)-2,3,14,22,25-pentahydroxy-cholest-7-en-6-one and 20-hydroxyecdysone (22R)-2,3, 14,20,22,25-hexahydroxycholest-7-en-6-one were detected during the critical development stages of this bisexual parasite: during the exponential growth phase to adult stage (day 11 postinfection) and during the sexual maturation of adult and egg laying (day 40 postinfection). The parasites released their ecdysteroid hormones in the biological fluids of the infected vertebrates as soon as six days postinfection. In addition, the time course of the ecdysteroid titer was correlated with the susceptibility or the innate resistance of the host to schistosome infection. Moreover, we demonstrated that after a schistomicide therapy, ecdysteroids from urine of infected children decreased markedly four days after drug administration. We also have demonstrated that immunization of rodents with an ecdysone-BSA complex led to the reduction of the worm burden. By in vitro studies, we have shown that the ecdysterone antibodies were able to kill the juvenile worms within 24 hr. In addition, we have demonstrated that the enzymes Superoxide dismutase (SOD, EC 1.15.1.1) were present in schistosomes and that the total Superoxide dismutase activities in both males and females could be correlated with the 20-hydroxyecdysone within parasites.     

Identification and Function of Prothoracic Exocrine Gland Steroids of the Dytiscid Beetles Graphoderus cinereus and Laccophilus minutus

The chemical composition of the prothoracic defensive secretion of the water beetles Graphoderus cinereus and Laccophilus minutus was examined by gas chromatographic–mass spectrometric analysis of trimethylsilylated gland extracts. The main components are 3,11-dihydroxy-5-pregnan-20-one in G. cinereus and 3,12-dihydroxy-5-pregnan20-one in L. minutus. Fully saturated pregnanes have not been found in the prothoracic defensive glands of dytiscids before. Based on tests with synthetic compounds, their biological role was examined in a feeding assay with the minnow Phoxinus phoxinus. Agar pellets containing either steroid strongly deterred feeding.     

Response of The Lacewing Chrysopa cognata to Pheromones of its Aphid Prey

The lacewing Chrysopa cognata, one of the principal predators of aphids in Korea, was tested for responses to the aphid sex pheromone components (4aS,7S,7aR)-nepetalactone and (1R,4aS,7S,7aR)-nepetalactol and the aphid alarm pheromone (E)--farnesene. Electroantennogram responses were obtained to the sex pheromone components but not to (E)--farnesene. The sex pheromone components were attractive in a Y-tube olfactometer assay and in field trials with water traps, but no attraction was observed to (E)--farnesene.     

Inhibition of β-Glucosidase and Esterase by Tannins from Betula, Salix, and Pinus Species

The reaction of tannin fractions isolated from the bark of Betula, Salix, and Pinus species with two enzymes, -glucosidase and esterase, was investigated. The influence of precipitation to the hydrolytic capacity of -glucosidase also was studied. All tannins studied precipitated -glucosidase and esterase, and moderate differences in the precipitating capacities of the tannins were observed. Interestingly, complex formation between -glucosidase and tannin did not markedly affect the activity of the enzyme. Therefore, complex formation during the insect/herbivore feeding does not necessarily change the defense activity of phenolic glycosides or decrease activity of digestive enzymes.     

Immobilization of β-Glucosidase on carbon nanotubes

Carbon nanotubes are demonstrated as a good support for the immobilization of -Glucosidase. This is an enzyme with high molecular weight (ca. 135 kDa). A high enzyme loading of 630 mg per gram of support was achieved in 12 h. The link between the enzyme and the carbon nanotubes surface was by electrostatic interactions due to the different charges of the enzyme and the support at the pH of the immobilization. Immobilized -Glucosidase showed a catalytic activity above 400 U/g on the hydrolysis of 4-nitrophenyl--D-glucopyranoside (p-NPG).     

Identification of Semiochemicals Released During Aphid Feeding That Attract Parasitoid Aphidius ervi

Herbivore induced release of plant volatiles mediating the foraging behavior of the aphid parasitoid Aphidius ervi was investigated using the pea aphid, Acyrthosiphon pisum, feeding on broad bean, Vicia faba. Behavioral responses were studied using an olfactometer and a wind tunnel. Volatiles obtained by air entrainment of aphid infested plants were more attractive to A. ervi than those from uninfested plants, in both behavioral bioassays. GC-EAG of both extracts showed a number of peaks associated with responses by A. ervi, but with some differences between extracts. Compounds giving these peaks were tentatively identified by GC-MS and confirmed by comparison with authentic samples on GC, using two columns of different polarity. The activity of pure compounds was further investigated by EAG and wind tunnel assays. Results showed that, of the compounds tested, 6-methyl-5-hepten-2-one was the most attractive for A. ervi females, with linalool, (Z)-3-hexen-1-yl acetate, (E)--ocimene, (Z)-3-hexen-1-ol, and (E)--farnesene all eliciting significantly more oriented flight behavior than a solvent control. Foraging experience significantly increased parasitoid responses to these compounds, with the exception of (E)--farnesene. Time-course GC analysis showed that feeding of A. pisum on V. faba induced or increased the release of several compounds. Release of two of these compounds (6-methyl-5-hepten-2-one and geranic acid) was not induced by the nonhost black bean aphid, Aphis fabae. During the analysis period, production of (E)--ocimene remained constant, but 6-methyl-5-hepten-2-one, linalool, geranic acid, and (E)--farnesene appeared during the first day after A. pisum infestation and increased in concentration with increasing time of aphid feeding.     

Isolation of 8-hydroxygeraniol-8-O-β-d-glucoside,a probable intermediate in biosynthesis of iridoid monoterpenes,from defensive secretions ofPlagiodera versicolora andGastrophysa viridula (Coleoptera: Chrysomelidae)

8-Hydroxygeraniol and its 8-O--d-glucoside have been found as trace components in the defensive secretions ofPlagiodera versicolora andGastrophysa viridula larvae. This discovery supports the hypothesis that the evolution of the utilization of plant precursors by some chrysomelid species was favored by the plesiomorphic occurrence of a-glucosidase and an oxidase in the defensive secretion of iridoid-producing species.     

Allelopathic Effects of Volatile Monoterpenoids Produced by <Emphasis Type="Italic">Salvia leucophylla</Emphasis>: Inhibition of Cell Proliferation and DNA Synthesis in the Root Apical Meristem of <Emphasis Type="Italic">Brassica campestris</Emphasis> Seedlings

Salvia leucophylla, a shrub observed in coastal south California, produces several volatile monoterpenoids (camphor, 1,8-cineole, -pinene, -pinene, and camphene) that potentially act as allelochemicals. The effects of these were examined using Brassica campestris as the test plant. Camphor, 1,8-cineole, and -pinene inhibited germination of B. campestris seeds at high concentrations, whereas -pinene and camphene did not. Root growth was inhibited by all five monoterpenoids in a dose-dependent manner, but hypocotyl growth was largely unaffected. The monoterpenoids did not alter the sizes of matured cells in either hypocotyls or roots, indicating that cell expansion is relatively insensitive to these compounds. They did not decrease the mitotic index in the shoot apical region, but specifically lowered mitotic index in the root apical meristem. Moreover, morphological and biochemical analyses on the incorporation of 5-bromo-2-deoxyuridine into DNA demonstrated that the monoterpenoids inhibit both cell-nuclear and organelle DNA synthesis in the root apical meristem. These results suggest that the monoterpenoids produced by S. leucophylla could interfere with the growth of other plants in its vicinity through inhibition of cell proliferation in the root apical meristem.     

Trail following and recruitment: Response of eastern tent caterpillarMalacosoma americanum to 5β-cholestane-3,24-dione and 5β-cholestan-3-one

Studies were conducted to determine the relative effectiveness of 5-cholestane-3,24-dione (diketone) and 5-cholestan-3-one (monoketone) in eliciting trail following from eastern tent caterpillars,Malacosoma americanum. In Y maze tests, trails prepared from the monoketone were followed preferentially over diketone trails, even when the diketone trail was several orders of magnitude stronger. Under field conditions, colonies readily abandoned well-developed trail systems in favor of artificial trails that were established with the monoketone. Other tests in which the caterpillars selected trails prepared from the monoketone (but not the diketone) more often than their own recruitment trails indicate that the monoketone constitutes the chemical basis of recruitment communication in this insect. The study also shows that tent caterpillars are highly sensitive to small differences in the amount of monoketone in a trail and can distinguish between new and aged trails prepared from the compound.     

Response of the Seven-spot Ladybird to an Aphid Alarm Pheromone and an Alarm Pheromone Inhibitor is Mediated by Paired Olfactory Cells

Electrophysiological responses of adult seven-spot ladybirds, Coccinella septempunctata, to (E)--farnesene, an aphid alarm pheromone, and (–)--caryophyllene, a plant-derived alarm pheromone inhibitor, were investigated by recording from single olfactory cells (neurons) on the antenna. Cells having high specificity for each of the two compounds were identified. Furthermore, these two cell types were frequently found in close proximity, with a larger amplitude consistently recorded for the cell responding specifically to (E)--farnesene. Preliminary behavioral studies in a two-way olfactometer showed that walking adults were significantly attracted to (E)--farnesene; this activity was inhibited with increasing proportions of (–)--caryophyllene. The possible ecological significance of colocation or pairing of olfactory cells for semiochemicals with different behavioral roles is discussed.