Václav Němec

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.

Analysis of pteridines in Pyrrhocoris apterus (L.) (heteroptera, pyrrhocoridae) during development and in body‐color mutants

By using thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC), five different pteridines have been quantified in extracts from Pyrrhocoris apterus: neopterin, isoxanthopterin, isoxantholumazine (violapterin), 7-methylxanthopterin, and erythropterin. Biopterin was also detected using HPLC. Pteridines have been analyzed separately in bodies and eyes of the wild type regarding developmental stage and sex. The pteridine content in both bodies and eyes increased from nymphs to 2-day-old adults. After this period, the concentration of pteridines in the eyes of adults remained approximately constant, while in the bodies isoxantholumazine, 7-methylxanthopterin, and isoxanthopterin kept increasing until 20 days. Considering the total amount of pteridines per insect, no qualitative or quantitative differences between males and females have been observed except a lower concentration of erythropterin in female bodies. But when pteridines are analyzed per unit body weight, a lower amount of pteridines is always detected in females due to its bigger size. A new body-color mutant, the yolk body mutant, that goes through developmental colour changes, was also analyzed during development, showing a general deficient accumulation of all pteridines, especially of 7-methylxanthopterin and isoxantholumazine in adult bodies. The effect on pteridine content of three other recessive (white, yellow, mosaic) and two dominant (Pale and Apricot) body-color mutations, has also been studied. A specific pteridine pattern different from the wild type was obtained for each mutant.

Identification of pteridines in the firebug, Pyrrhocoris apterus (L.) (Heteroptera, Pyrrhocoridae) by high -performance liquid chromatography

Abstract Pteridines in the wild type of Pyrrhocoris apterus were investigated by high-performance liquid chromatography (HPLC). Five different pteridines were identified: neopterin, biopterin, isoxantholumazine (violapterin), isoxanthopterin, and 7-methylxanthopterin. Biopterin and neopterin have been found in P. apterus for the first time. No qualitative or quantitative differences were observed between pteridine patterns in males and females. The present paper represents the first identification and quantification of P. apterus pteridines using HPLC.

Control of Cacopsylla (Psylla) pyri (L.) (Stenorhyncha, Psyllidae) by juvenile hormone analogues.

Juvenoids could be a useful tool for the control of psyllids. The 12 new juvenoids synthetized at the Institute of Organic Chemistry and Biochemistry in Prague were tested by dipping the feeding plants in the juvenoid solution and by indirect contact application on Cacopsylla (Psylla) pyri (L.). The tested compounds were mostly less active than the commercial juvenoid, methoprene. However, even the low doses of active juvenoids which evoked only small malformations on wings and external genitalia of the treated psyllids disabled them from flying and also from copulation. The most sensitive period for juvenoids in psyllids comprises the first 4 days of the last larval instar. Aside from this period, juvenoids failed to evoke any malformation. The investigated juvenoids were also tested on the main predator of psyllids, the pirate bug, Anthocoris nemoralis (Fabr.), using the indirect topical application. It was found that the sensitive period of these bugs to the tested juvenoids is restricted to the first 24 h of the last larval instar. Hence, the pirate bug revealed very low sensitivity to the tested juvenoids.

Distribution and excretion of juvenoid in the locust Locusta migratoria migratorioides (R. et L.) (Orth., Oedipodinae)

The distribution and the excretion rate of topically administered 3H and 14C‐labelled juvenoids, derivatives of 2‐(4‐hydroxybenzyl)‐1‐cycloalkanone were analyzed in the last instar nymphs and imagoes of the African migratory locust, Locusta migratoria migratorioides. It was found that the main process of elimination of juvenoid is the excretion. About 80% of the total applied label was excreted within the first 2 days after topical application. The maximum quantity of the topically applied juvenoid penetrated in the locust body within the first 2 days after application. However, the administered juvenoid was deposited in cuticle for a long time. It was found that 7–8% of the total applied label was deposited in cuticle (exuvies) that have been casted off after 12 days from application. In the other analysed organs (brain, fat body, thoracic muscles, intestine, gonads, haemolymph) only a small part of the administered radioactivity was found.