Conformational analyses of periplanone analogs by molecular mechanics calculations

Conformational parameters of pheromonally active analogs (1 and 2) of periplanones, the sex pheromones of the American cockroach, were investigated by molecular mechanics calculations. They existed in several conformers with small energy differences. These results were supported by NMR analysis. The structural features of the conformers of the analogs were compared with X-ray structures of periplanones.     

Behavioral responses of malePeriplaneta americana to periplanone B,a synthetic component of the female sex pheromone

Bioassays were performed on malePeriplaneta americana L. using concentrations of (±)-periplanone B of 10^–9-10^–3 g and a serial dilution of natural female sex pheromone extract. Synthetic (±)-periplanone B stimulated the complete repertoire of behavior released by the extract: increased rate of locomotion, upwind orientation, and the wingraising component of courtship display. Quantitative behavioral comparisons of the activity of natural extracts prepared by this and other laboratories are possible by the standardization of the stimulus in terms of g of (±)-periplanone B applied per assay.     

Behavioral responses of malePeriplaneta americana L. to female sex pheromone components,periplanone-A and periplanone-B

Bioassays were performed on malePeriplaneta americana L. using synthetic (–)-periplanone-B (P-B) and Hauptmann's (–)-periplanone-A (P-A), and their mixtures at various ratios to estimate the roles of both periplanones for the sexual communication of the species. Both P-A and P-B elicited qualitatively the same responses, such as antennal movement, rapid locomotion, wing raising, and homosexual behavior of male cockroaches, but the threshold of the pheromone activities for P-B was two orders of magnitude lower than that of P-A. Neither synergistic nor inhibitory but only a simple integrated effect on the responses was observed when mixtures of P-A and P-B were applied.     

Electroantennogram responses of synthetic periplanone-A and periplanone-B in the american cockroach

The electroantennogram responses of synthetic (–)-periplanone-B (PB) and (–)-periplanone-A (PA) were evaluated by using the antennae of the unmated male American cockroachPeriplaneta americana L. The threshold concentrations of the pheromone activities for the two chemicals were similar. Neither a synergistic nor an inhibitory response was noted, and only an additive effect was detected when PA and PB were applied as a mixture.     

Empirical correlations between electroantennograms and bioassays forPeriplaneta americana

Determination of electroantennograms (EAGs) with an electroantennometer having a positive and a negative peak detection option, and with a stimulus delivery device providing local stimulation of the antenna ofP. americana, allowed for the detection of three typical EAG patterns for a wide range of compounds tested. Some of the compounds presented at least one positive EAG peak (0.1–0.3 mV), others showed a single negative EAG peak (–1.0 to –1.1 mV), and a third group had more than one negative EAG peak (–0.2 to –0.8 mV). These EAG results correlate with behavioral assays ofP. americana. Thus compounds having a positive EAG response act as repellents, while those having negative EAG responses act as attractants, depending on concentration. EAG patterns thus can permit prediction of behavioral responses ofP. americana.     

Studies on relationship between activity and electron density on carbonyl oxygen in sex pheromone mimics of the American cockroach,part XI

From the relationship between structures of the 2-substituents of verbanyl analogs and their sex pheromone activities to the American cockroach, electron density of the carbonyl oxygen atom in the substituent, as estimated by the [¹⁷O]NMR chemical shift, was estimated to be an important factor which influenced the activity, in addition to length of the substituent and the position of the carbonyl group. (+)-Verbanyl methylcarbonate (XX), possessing the highest electron density on the carbonyl oxygen atom, showed the strongest activity among the analogs.For Part X, see Manabe et al., 1983. J. Chem. Ecol. 9:533–549.     

Attraction responses of the American cockroach to synthetic periplanone-B

Synthetic periplanone-B has been shown not only to be a sex excitant to malePeriplaneta americana by bioassay in the laboratory but also an attractant pheromone by field tests in a rice storage house in Taipei. During both summer and winter months, it attracted signincantly more adult males into the traps used in the experiments than adult females. There is a statistically significant increase in the sex ratio (male-female) of the trapped adults with increase in periplanone-B used. An attempt has been made to explain the trapping of females and nymphs in addition to males by the chemicals used in our tests.     

Sex pheromonal activity of (+)-trans-verbenyl acetate and related compounds to the american cockroach,Periplaneta americana L.

The sex pheromone mimic of the American cockroach, (+)-trans-verbenyl acetate, and 67 synthesized analogs were tested for sex pheromonal activity using males of the cockroach. Only three esters in addition to the original (+)-trans-verbenyl acetate exhibited activity. (+)-trans-Verbenyl propionate and (+)-verbanyl acetate in particular showed stronger activity than the original mimic. None of the other analogs caused a response at the 1-mg level. The lower threshold levels at which even the most active analogs showed activity (0.02 mg) were many orders of magnitude higher than that of the natural pheromone, periplanone-B (10^–8 mg). From the structure-activity relationships, important structural factors for sex pheromonal activity in the original mimic were discussed.Studies on the sex pheromone mimic of the American cockroach, (+)-trans-verbenyl acetate. Part VI. For Part V,Agric. Biol. Chem. 44:2877 (1980).     

Sex pheromone-stimulated orientation of the American cockroach on a servosphere apparatus

Sex pheromone of the American cockroach,Periplaneta americana L., Orthoptera: Blattidae, stimulates positive anemotaxis and increased running speed when presented in an air stream. Locomotory pathways recorded from a servosphere device show that both straightness and direction of movement are concentration dependent. Cockroaches are apparently able to employ chemotaxis perpendicular to the wind while moving upwind by chemoanemotaxis.     

Sex pheromone-induced chemolocation in the male American cockroach,Periplaneta americana

Males of the American cockroach,Periplaneta americana, have evolved an efficient search strategy enabling them to locate a source of sex pheromone in the absence of directional information derived from wind. Since these animals are able to utilize chemotaxis to orient almost directly to the source from 45–50 cm away, it is only necessary that they maximize their chances of getting within that range once they perceive the pheromone. They accomplish this by: (1) increasing their overall levels of activity and (2) initiating local search. In this way, they are able to cover a rather large area in a short period of time, i.e., before the source female changes location. If their paths take them to within 45 cm of the source, they are able to locate it soon thereafter. It is probable that very similar strategies are utilized by many other nonflying insects to locate sources of airborne odors.     

Evidence for the Site of Female Sex Pheromone Production in Periplaneta americana

We used bioassays to determine the sex pheromone production site in the female American cockroach (Periplaneta americana). Bioassayed extracts from various body parts aroused sexual responses from unmated males. However, the extract of hindgut (including both colon and rectum) induced strong responses. Colon extract stimulated the strongest sexual response. To compare the sex pheromone contents of atrial glands, pygidium, rectum, and colon, we recorded the EAG responses of male antennae to these extracts. Among the four tissues, colon extract caused the strongest EAG response. From gas chromatographic (GC) analysis, the quantities of periplanone-A (PA) and periplanone-B (PB) (the main sex pheromone components in female American cockroach) were 0.34 and 8.31 ng, respectively, in the colon of a virgin female. The ratio of PA to PB was ca. 1:24. The present results are different from those reported in a previous study, in which it was concluded that atrial glands are the sites of sex pheromone production in P. americana, and from GC analysis the quantity of PB was estimated to be 60 ng/female. There was no difference in sexual behaviors induced by colon and atrial glands of calling virgin females. It is unclear whether the colon is the sole sex pheromone source in the female American cockroach.     

Behavioral and electrophysiological responses of the brownbanded cockroach,Supella longipalpa,to stereoisomers of its sex pheromone,supellapyrone

Females of the brownbanded cockroach, Supella longipalpa, release a sex pheromone (supellapyrone) during a calling behavior and attract males from a distance. Supellapyrone has four possible configurations resulting from two asymmetric carbons at positions 2 and 4 (i.e., 2R,4R; 2R,4S; 2S,4R; and 2S,4S), but only the RR isomer is produced by females. Using pure synthetic stereoisomers in field tests, we showed that males are attracted to RR but also to high concentrations of the isomer SR. To study the activity of the stereoisomers in more detail we developed behavioral and electroantennogram (EAG) dose–response curves for each. Behaviorally, RR was the most active isomer with just 0.3 pg delivered on a filter paper being sufficient to elicit 50% male response in the olfactometer. Males were also attracted to SR and SS in the olfactometer, but at much higher dosages (100×) than the natural compound; RS did not elicit behavioral responses at any of the doses tested. In EAG assays, the antenna of male S. longipalpa showed high and similar sensitivity to RR and SR, but a much lower (10%) sensitivity to SS and practically no response to RS. The lack of agreement between behavioral and electrophysiological data suggested either that RR and SR stimulate different antennal sensory neuron types, or that some aspect of the interaction between the pheromone and the sensillum environment or the receptor neuron itself is different. To test the first hypothesis we examined the response of the antenna before and after adaptation with each of the four stereoisomers. Positive cross-adaptation between RR and SR suggests that these two compounds stimulate the same receptor cells. Therefore, the lack of agreement between behavioral and EAG dose–response curves could be explained by isomer-specific molecular interactions between the pheromone and the receptor neuron. Although RR and SR produced the same EAG amplitude, stimulation with SR resulted in a slower recovery rate (i.e., wider peaks) than stimulation with RR. To gain further understanding of the response specificity of the antennae to the different stereoisomers we compared EAG responses (amplitude and recovery time) in response to individual stereoisomers and binary mixtures of isomers. These tests showed additive responses of the EAG amplitude to mixtures of compounds, but nonadditive responses of EAG recovery time. Therefore, peak height and width are independent parameters of the EAG, probably representing different intrasensillar events, and likely resulting in the expression of different behavioral responses.     

The attractivity of the female sex pheromone ofPeriplaneta americana and its components for conspecific males and males ofPeriplaneta australasiae in the field

The attractivity of virgin female odors of the American cockroach was examined in field experiments. Crude extracts of the female odor, the isolated sex pheromone fractions, periplanone-A and periplanone-B, and other compounds obtained during the isolation served as stimulants. An extract of male odors, obtained by identical collection methods, was used as a control. Males ofPeriplaneta americana were attracted by the crude extract and periplanone-B; males of the sympatric species,P. Australasiae, by periplanone-A. Experiments in which these components were presented subsequently and as mixtures indicate that, under certain conditions, periplanone-A may also function as an attracting substance forP. americana males and that periplanone-B and possibly some other components act as an inhibitor for males ofP. australasiae.     

Effects of sex pheromone on locomotion in the male American cockroach,Periplaneta americana

The locomotory activities of individual males ofPeriplaneta americana in a circular arena 2.5 m in diameter were investigated during the portion of the photocycle in which the cockroaches are most active. Control animals ran at an average speed of 10.86 cm/sec but remained immobile 68 % of the time. Pauses in locomotion occurred frequently and at fairly regular intervals (x=0.88 sec). Males showed a strong tendency to remain near the sides of the arena. Sex pheromone presented in the center of the arena produced a reduction in immobility time and a slight increase in running speed. The frequency of pauses decreased, and the time between pauses became less regular. The proportion of time spent near the sides of the arena was greatly reduced also.     

Studies on sex pheromone of American cockroach,with emphasis on structure elucidation of periplanone-A

Two independently biologically active compounds, periplanone A and periplanone B can be isolated from fecal material of the American cockroach,Periplaneta americana. In fecal material these occur in a ratio of 1 10 while, in intestinal tracts only periplanone B has been found. The latter has been identified as (1Z,5E)-1,10(14)-diepoxy-4(15),5-germacradien-9-one; the identification was confirmed by synthesis. Only the CD (–) enantiomer (1R,2R,5E,7S,10R) exhibited activity. The lower threshold of activity of both natural and synthetic CD (–) pheromone, is 10^–6–10^–7 g. Periplanone A has been identified (apart from its stereochemical configuration) as 7-methylene-4-isopropyl-12-oxa-tricyclo[4.4.2.0^1,5]-9-dodecen-2-one). The structure of this rather unstable compound could be deduced by comparing its NMR, UV, IR, and mass spectra with the NMR and mass spectra of its rearrangement product. Both structures still require confirmation by synthesis, but their spectral data are in complete agreement with the proposed structures. The presence of only periplanone B in the gut and the presence of both periplanone A and periplanone B in the feces suggests that periplanone B is a genuine sex pheromone, whereas peri-planone A might be a biologically active transformation product, which in turn can isomerize into a more stable, but inactive compound.     

Behavioral and electrophysiological evidence for volatile sex pheromones in Parcoblatta wood cockroaches

Species within the cockroach genus Parcoblatta are sexually dimorphic for wing length; females have reduced wings and are flightless, while males have long wings that are used in flight. We predicted that Parcoblatta females would release a volatile sex pheromone to attract the more mobile males. Nymphs of the broad wood cockroach, P. lata, and the Caudell's wood cockroach, P. caudelli, were collected in forested areas in North Carolina, USA, and reared in the laboratory for observations of sexual behavior and for pheromone analysis. After several days of sexual maturation, virgin females of both species exhibited distinct calling behaviors. In females of P. lata, calling commenced 6 days after adult emergence. Under a light–dark photoperiod regime, calling behavior in both species was restricted to the scotophase. Calling consisted of a repeated pattern of raising and lowering the abdomen with occasional exposure of the genital vestibulum. To test whether calling behavior is associated with the release of pheromone, volatiles from calling and noncalling females were collected on Super-Q and tested by electroantennogram (EAG) and behavioral assays. Volatile collections from calling females elicited higher male-specific EAG responses than collections from noncalling females of the same physiological stage. In an olfactometer choice test (Y-tube), males preferred volatiles from calling females over those from noncalling females. To determine the anatomical source of the pheromone, solvent extracts of various body parts were analyzed by EAG. The first through seventh tergites were the only body parts that elicited male-specific EAG responses in both species. In P. lata, the activity of the extract increased from 1- to 7-day-old females, but was lower in mated than in virgin females of the same age. The putative pheromone gland appears to consist of numerous class-3 secretory units, each composed of a secretory cell connected to a cuticular pore via a tubular duct. We conclude that female P. lata and P. caudelli produce sex-specific volatile pheromones that are emitted during calling behavior.     

Antennnal olfactory and behavioral response of southern pine beetle,Dendroctonus frontalis,to analogs of its aggregation pheromone frontalin

Antennal olfactory (electroantennogram) and laboratory and field behavioral tests were carried out on the response ofDendroctonus frontalis to its aggregation pheromone frontalin and analogs. The analogs were compounds modified by altering the position and methyl groups and/or by their deletion. Any modification to the frontalin structure significantly reduced both the antennal olfactory and behavioral response byD. frontalis. Beetle response, although significantly reduced, was elicited at the receptor level and in a laboratory bioassay by all analogs. However, only one analog (endo-5,7-dimethyl-Frontalin) elicited significant response from field populations of the beetle.Texas Agricultural Experiment Station paper TA-22507. The work was funded in part by McIntire-Stennis project 1525 and by an operating grant from the Alberta Forest Service through the Forest Development Research Trust Fund. The findings, opinions, and recommendations expressed are those of the authors and not necessarily those of the U.S. Department of Agriculture. All programs and information of the Texas Agricultural Experiment Station are available without regard to race, ethnic origin, religion, sex, or age.     

Haloacetate analogs of pheromones: Effects on catabolism and electrophysiology inPlutella xylostella

A series of mono-, di-, and trihalogenated acetate analogs of Zl 1–16: Ac were prepared and examined for electrophysiological activity in antennae of males of the diamondback moth,Plutella xylostella. In addition, two potential affinity labels, a diazoacetate (Dza) and a trifluoromethyl ketone (Tfp), were evaluated for EAG activity. The Z11–16Ac showed the highest activity in EAG assays, followed by the fluorinated acetates, but other halo-acetates were essentially inactive. The polar diazoacetate and the trifluoromethyl ketone were also very weak EAG stimulants. The effects of these analogs on the hydrolysis of [³H]Z11–16Ac to [³H]Z11–16OH by antennal esterases was also examined. The three fluorinated acetates showed the greatest activity as inhibitors in competition assays, with rank order F₂Ac > F³Ac > FAc > Ac > Cl₂Ac > ClAc > Dza > Br₂Ac > BrAc > Tfp > I > Cl₃Ac > Br₃Ac > OH. The relative polarities of the haloacetates, as determined by TLC mobility, are in the order mono- > di- > trihalo, but F, Cl, Br, and I all confer similar polarities within a substitution group. Thus, the steric size appears to be the predominant parameter affecting the interactions of the haloacetate analogs with both receptor and catabolic proteins inP. xylostella males.On leave from Institute of Organic Chemistry, Czechoslovak Academy of Science, Flemingovo namstí 2, 16610, Prague, Czechoslovakia.     

Moth responses to selectively fluorinated sex pheromone analogs

Partially fluorinated analogs of the European corn borer (Ostrinia nubilalis) female sex pheromone, 11-tetradecenyl acetate (97:3Z:E), having mono- and trifluorsubstitutions at the terminal carbon of the pheromone chain, mimicked the biological activity of the pheromone, while analogs with fluorine at either side of the double bond and a pentafluoro analog were essentially inactive. Comparison of the pheromonal activity of these analogs with the previously reported activity of similarly fluorinated pheromones in five other species of moths revealed an unpredictable relationship between fluorine substitution pattern and pheromone-mimicking activity. Fluorine substitution patterns that rendered pheromonal analogs biologically inactive in the European corn borer had no detrimental influence upon pheromonal activity in other species and the converse was also true. This is evidence that the relative importance of electronic qualities of sites within a pheromone molecule differ from species to species. Furthermore, it indicates that the biochemical components (pheromone receptor proteins, binding proteins, and enzymes) that make up moth olfactory chemosensory systems must also vary structurally from species to species, despite the fact that they are involved in olfactory sensing of compounds having very similar chemical structure.     

Factors influencing male sexual response in the American cockroachPeriplaneta americana

Male sexual response inPeriplaneta americana is influenced by the presence or absence of sex pheromone, the length of time since last exposure to pheromone, the length of that exposure, and the photocycle. Females begin emission of sex pheromone 9 or more days after the molt to adult. The quantity emitted does not appear to be influenced by the photocycle. During the light phase of the photocycle, males only respond to high concentrations of pheromone. They recover quickly after brief exposures, but after prolonged exposures, a second exposure 24 h later elicited responses of lower intensity.