Jelena Kuldová

A Series of Bicyclic Insect Juvenile Hormone Analogs of Czech Origin: Twenty Years of Development

Research results are summarized from a series of insect juvenile hormone analogs derived from 2-(4-hydroxybenzyl)-1-cycloalkanones, which have been investigated at the Institute of Organic Chemistry and Biochemistry in Prague during the past 20 years. At present, practical application of several prospective structures for insect control is under investigation. Biological activity values were determined to delineate the most important subseries of compounds and the most promising insect juvenile hormone analogs selected from the subseries. Carbamates, and in particular compound 47 proved to be highly active against aphids, cockroaches, flies, and many other insect species.

Sex Pheromone of Horse-Chestnut Leafminer Cameraria ohridella and Its Use in a Pheromone-Based Monitoring System

Gas chromatography combined with electroantennographic detection (GC-EAD), electroantennography (EAG), and wind-tunnel and field experiments were used to reinvestigate the composition of Cameraria ohridella (Lepidoptera, Gracillariidae, Lithocolletinae) sex pheromone. The GC-EAD experiments showed one EAD-active area corresponding to the major pheromone component, (8E,10Z)-tetradeca-8,10-dienal. The EAG experiments proved that (9E)-tetracedecenal and stereoisomers of (8E,10Z)-tetradeca-8,10-dienal exhibited significant electrophysiological activity and could, therefore, be considered as possible minor pheromone components. However, wind-tunnel and field experiments demonstrated that none of these compounds affect the efficacy of the main pheromone component. A monitoring system based on (8E,10Z)-tetradeca-8,10-dienal was developed and used to study the flight activity of C. ohridella.

Fatty Acid Esters of Juvenoid Alcohols as Insect Hormonogen Agents (Juvenogens)

A series of 8 new juvenogens (3--10) was prepared starting from a pair of isomeric insect juvenile hormone bioanalogues ( and ). The biological activity of the juvenogens -- was tested for their effect on reproduction of the blowfly Neobellieria (Sarcophaga) bullata and for the juvenilizing activity on the termite Prorhinotermes simplex. Results of biological screening are important in structure--activity studies and promising for potential practical application of some of the juvenogens studied, especially against termites.

A juvenile hormone analogue with potential for termite control: laboratory tests with Reticulitermes santonensis, Reticulitermes flaviceps and Coptotermes formosanus (Isopt., Rhinotermitidae)

Laboratory experiments with three species of termites were conducted to study the efficacy of a carbamate derivative of 2‐(4‐hydroxybenzyl)‐1‐cyclohexanone (W‐328). The compound has been found to be highly active causing differentiation of termite workers into presoldiers, soldiers and/or soldier‐intercastes. Differentiation of excessive soldiers induced by juvenile hormone analogues (JHAs) may disrupt the social homeostasis and consequently cause death of the whole termite colony. W‐328 induced differentiation into soldiers in 41–100% of individuals when applied in range of 50–500 ppm to a feeding substrate of wood in force‐feeding and choice bioassays with groups of Reticulitermes santonensis Feytaud and R. flaviceps (Oshima). Efficacy of W‐328 was also confirmed in choice bioassays with isolated groups of workers and soldiers and with incipient colonies of Coptotermes formosanus Shiraki. A high proportion of JHA‐induced differentiation into soldier caste was accompanied by increased mortality. Termites accept a matrix treated with W‐328 quite well. Significant feeding deterrence of the compound was observed only at higher concentrations: 500 ppm in some tests with Reticulitermes spp. and 5000 ppm in colonies of C. formosanus. Adequate persistence of W‐328 in corrugated cardboard (a potential feeding substrate for baits) was confirmed by bioassay with R. santonensis and by chemical analysis. The residue levels of the compound, applied at 500 ppm concentration, after 27 days of conditioning remain high enough to result in significant soldier differentiation.

Defense secretion of Prorhinotermes simplex : Toxicity to insecticide susceptible and resistant house fly

Abstract(E)-1-Nitropentadec-1-ene (NPE), the main component of the defense secretion of Prorhinotermes simplex soldiers, is toxic to both insecticide-susceptible (S) as well as to insecticide-resistant (R) strains of the house fly, Musca domestica. The LD50 is 11.7 μg/female fly for the S strain and 9.7 μg for the R strain. The same efficacy of NPE on R and S strains indicates a different mechanism of action compared to conventional chlorinated, organophosphorus, and pyrethroid insecticides. Termite nestmates are protected against NPE by a specific detoxification mechanism. 1-Nitropentadecane, the detoxification product of NPE is nearly nontoxic to house flies, and doses up to 160 μg/fly caused only very low mortality.

Optically active juvenoids derived from 2-substituted cyclopentanol and their biological activity on Tenebrio molitor

Abstract Optically active juvenoids 1c – 4c were synthesised using chiral precursors prepared by biotransformation reactions of suitable substrates. Biological activity of these juvenoids on Tenebrio molitor is reported.

Response of the hop aphid, Phorodon humuli (Homoptera: Aphididae), to the application of juvenile hormone analogue in field trials

Abstract Efficacy of the carbamate-moiety based juvenile hormone analogue W-328 against the hop aphid, Phorodon humuli (Schrank), was studied. As an effective development and reproduction regulator of aphids in laboratory experiments, it affected hop aphid populations when sprayed as 0.1 and 0.01% water emulsion on hop seedlings in a small-scale field trial. Populations declined within the first 10 days and were almost wholly suppressed after a month. The efficacy of 0.1% emulsion of W-328 sprayed on individual hop plants in an orchard was similar, but in a field trial in a commercial orchard, with high-trellis hops, after a 0.05% emulsion spray, only aphids on the middle and bottom parts of plants were suppressed, while aphids on the upper newly grown untreated shoots were unaffected. The potential of using juvenile hormone analogue W-328 against the hop aphid in an integrated pest management strategy is discussed.

TheMichael-Type Addition Reaction: A Stereocontrolled Construction of a New Quaternary Chiral Center at C(2) of 2-(4-Hydroxybenzyl)cyclohexanone Derivatives

The Michael-type addition reaction was used as a convenient method for the stereocontrolled construction of a new quaternary C-center at position 2 of 2-substituted cyclohexanones (Scheme) with the aim to study the effect of an additional substituent at C(2) in a series of biologically active compounds bearing generally a 2-substituted cyclohexanone moiety. Thus, a new series of compounds consisting of a racemate (RS)-12 and its enantiomers (S)- and (R)-12 (ee ≥96% for both enantiomers) was obtained. The Michael adduct derivatives (S)-, (R)-, and (RS)-12 were subjected to a biological screening using several non-related insect species.