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Extended Summaries : 9th Pesticide Chemistry Congress

309

TABLE 2 Insecticidal Activity of Substituted 2-Nitroiminoimidazolidines and Reference Compounds Insecticidal activitya Pest

Stageb

Concentration (mg AI litre~1)

Spodoptera littoralis Diabrotica balteata Heliothis virescens Aphis craccivora Myzus persicae Nilaparvata lugens T etranychus urticae

L1 L3 L1 m.p. m.p. N3 m.p.

100 100 100 100 12É5 100 100

1

2a

2b

2c

5a

5b

]] ]] ]] ]] ]] ]] [

[ [ [ [ [ [ [

[ [ [ [ [ [ [

[ [ [ [ [ [ [

[ [ [ [ [ [ [

[ [ [ [ [ [ [

5c

8a

8b

[ [ [ [ [

]] ]] [ [ ]] ]] [

]] ]] [ [ ]] ]] [

a ]] [80% mortality ; [ \30% mortality. b L1 : Ðrst-instar larvae, L3 : third-instar larvae, m.p. : mixed population, N3 : third-instar nymph.

D. balteata : Corn seedlings in a Petri dish were treated with test solutions pipetted into the dish and then infested with third-instar larvae. Samples were checked six days after treatment for mortality and growth regulation. H. virescens : Eggs (0È24 h old) on Ðlter paper were placed in Petri dishes on top of a layer of artiÐcial diet and treated with test solutions introduced by pipette. After six days incubation, samples were checked for egg mortality, larval mortality and growth regulation. A. craccivora : Pea seedlings, infested with a mixed population were treated with test solutions in a spray chamber. Samples were checked six days after treatment for mortality (contact activity). M. persicae : Pea seedlings, infested with a mixed population were placed directly in the test solutions. Samples were checked six days after introduction for mortality (systemic activity). N. lugens : Rice seedlings were treated in a spray chamber with test solution, dried and infested with third-instar nymphs. The samples were checked six to 12 days after the treatment for mortality, growth regulation and e†ects on F-1 generation. T . urticae : Bean leaf discs on agar in Petri dishes were infested with a mixed population, and, one day later, were treated with test solution in a spray chamber. Samples were checked for egg mortality, larval mortality, and adult mortality after 10 days incubation. 3 Results and discussion Table 2 shows the results of insecticidal tests of some new substituted 2-nitroiminoimidazolidines in comparison to imidacloprid (1). Compounds 2aÈc and 5aÈc, were relatively inactive, in contrast to compounds 8aÈb which were active at 100 mg AI litre~1 (contact) and 12É5 mg AI litre~1 (systemic). These results clearly demonstrate that the 5-(2-chloropyridyl)methyl group is necessary for biological activity. The mode of action of 8aÈb is probably similar to that of other neonicotinoid insecticides.6 Further tests were carried out with these compounds, but their activity was clearly poorer than

the imidacloprid standard, so the study was discontinued. Acknowledgements We wish to thank Dr P. MaienÐsch and Mr A. Rindlisbacher of Novartis Crop Protection for carrying out the biological tests, and for helpful and stimulating discussions and suggestions. References 1. Yamamoto, I., Agrochem. Jpn, 68 (1996) 14È5. 2. Kagabu, S. & Matsuno, H., J. Agric. Food. Chem., 45, (1997) 276È81. 3. Tomlin, C. (ed.) T he Pesticide Manual, 11th edn. Crop Protection Publications, The Royal Society of Chemistry, 1994, pp. 706È8. 4. McKay, A. F. & Wright, G. F., J. Am. Chem. Soc., 70, (1948) 430È1. 5. Hassner, A. & Dehaen, W., J. Org. Chem., 56 (1991) 896È 900. 6. Yamamoto, I., Tomizawa, M., Saito, T., Miyamoto, T., Walcott, E. C. & Sumikawa, K., Arch. Insect Biochem. Physiol. 37 (1998) 24È32.

Structure Elucidation of Omphalotin, a Cyclic Dodecapetide with Potent Nematicidal Activity Isolated from Omphalotus olearius Edwin BuŽchel,1 Anke Mayer,1 Heidrun Anke1 & Olov Sterner2*

Ulrike

Martini,1

1 LB Biotechnology, University of Kaiserslautern, D-67663 Kaiserslautern, Germany 2 Department of Organic Chemistry 2, Lund University, PO Box 124, S-22100 Lund, Sweden

Abstract : The structure and absolute conÐguration of omphalotin, a cyclic dodecapeptide isolated from the basidiomycete fungus Omphalotus olearius and possessing potent and selective activity against the plant pathogenic nematode Meloidogyne incognita, was determined by a combination of

310 spectroscopic and chemical techniques. ( 1998 Society of Chemical Industry Pestic. Sci., 54, 000È000 (1998) Key words : Omphalotus olearius ; omphalotin A ; cyclic dodecapeptide ; nematicidal ; structure determination ; absolute conÐguration

1 Introduction Omphalotin exhibits strong nematicidal activity against the plant pathogenic nematode Meloidogyne incognita (Kof. & White) Chitwood (LD 0É57 lM) while being 50 only weakly active against the saprophytic nematode Caenorhabditis elegans Maupas (LD 19 lM).1 In addi50 tion, it is only weakly cytotoxic at 100 lg ml~1 and shows no phytotoxic, antibacterial or antifungal activities.1 Omphalotin, which, following the recent isolation of omphalotins B, C and D, has been renamed omphalotin A,2 is a cyclic dodecapeptide isolated from cultures of the basidiomycete fungus Omphalotus olearius Sing. Initially, the structure was determined by twodimensional NMR spectroscopy without assignment of the relative or absolute stereochemistry.3 In this summary, we describe further details about the structure elucidation. 2 Experimental methods [1H]NMR (500 MHz) and [13C]NMR (125 MHz) spectra were recorded at room temperature with a Bruker ARX500 spectrometer with an inverse multinu-

Extended Summaries : 9th Pesticide Chemistry Congress clear 5-mm probehead equipped with shielded gradient coil. COSY, HMQC and HMBC experiments were recorded with gradient enhancements using sine-shaped gradient pulses. For the two-dimensional heteronuclear correlation spectroscopy the refocusing delays were optimised for 1J \145 Hz and nJ \10 Hz. CH CH 3 Results and discussion Due to the fact that nine of the 12 a-nitrogens are methylated, the omphalotins are relatively lipophilic cyclopeptides, and soluble in most organic solvents. However, they can exist in several conformations, and the stability of various conformers is a†ected by the solvent. In general, the data obtained in deuteromethanol were most suitable for the determination of the structures. In establishing the structure of the 36membered ring, the long-range 1H-1H (COSY) couplings between the N-methyl groups and the a-hydrogens, as well as the long-range 1H-13C (HMBC) couplings between the N-methyl groups and the carbonyl carbons and the a-carbons, and between the a-hydrogens and the neighbouring carbonyl carbon and the carbonyl carbon attached to the nitrogen, were crucial. The signals for the 12 carbonyl carbons are very close in frequency in deuterochloroform (as well as in other solvents),3 and insufficient resolution is obtained in a standard HMBC experiment. However, by decreasing the 13C sweep width to approximately 20 ppm it was possible to resolve all correlations from both the Nmethyl groups and the a-hydrogen atoms. In summary, all the correlations indicated in Fig. 2 could be observed, and established the macrocyclic ring unambiguously. The nine groups attached to the a-carbons could also be identiÐed by a combination of COSY and HMBC experiments. Hydrolysis of omphalotin and analysis of the amino acids showed that they are all L-amino

Fig. 1. Structure of omphalotin (omphalotin A). Arrows indicate the positions in which omphalotins B, C and D have been oxidised or oxidised/derivatised. * To whom correspondence should be addressed. E-Mail : Olov.Sterner=orgk2.1th.se Contract/grant sponsor : Bayer AG, Leverkusen Contract/grant sponsor : BMBF, Bonn Contract/grant sponsor : Swedish Science Research Council

Fig. 2. HMBC correlations observed that establish the molecular frame of the omphalotins.

Extended Summaries : 9th Pesticide Chemistry Congress acids,2 and the stereostructure presented in Fig. 1 represents the absolute conÐguration of omphalotin. Although it has not yet been proved, it is reasonable to assume that omphalotin is the biogenetic precursor of the oxidised omphalotins (B, C and D).2 In fact, the omphalotins B, C and D always appear after omphalotin during fermentations. Acknowledgements We are grateful to Ms A. Me†ert for expert technical assistance. Financial support from Bayer AG, Leverkusen, the BMBF, Bonn, and the Swedish Science Research Council is gratefully acknowledged. References 1. Mayer, A., Anke, H. & Sterner, O., Omphalotin, a new cyclic peptide with potent nematicidal activity from Omphalotus olearius. I. Fermentation and biological activity. Nat. Prod. L ett., 10 (1997) 25È32. 2. BuŽchel, E., Martini, U., Mayer, A., Anke, H. & Sterner, O., Omphalotins B, C and D, nematicidal cyclopeptides from Omphalotus olearius. Absolute conÐguration of omphalotin A. T etrahedron, 54 (1998) 5345È52. 3. Sterner, O., Etzel, W., Mayer, A. & Anke, H., Omphalotin, a new cyclic peptide with potent nematicidal activity from Omphalotus olearius. II. Isolation and structure determination. Nat. Prod. L ett., 10 (1997) 33È8.

Evidence of an Attractant from Virgin Females of Bephratelloides pomorum (Hymenoptera : Eurytomidae) : Possible Role of Cuticular Compounds Ruth R. do Nascimento,* Ivanildo S. de Lima, Claudia M. L. de MendoncÓa, Luciano C. N. da Silva, Adriana G. Duarte & Antoünio E. G. SantÏAna

311 Key words : Annona sp. ; Bephratelloides sp. ; GC-MS ; attractants

1 Introduction In the north-east of Brazil, the Annona seed borer Bephratelloides pomorum (Hymenoptera : Eurytomidae) is the most important insect pest of soursop, Annona muricata L. The female oviposits into the most recently formed seeds of developing fruit, which serve as food for the larvae. When fully developed, the young wasps start to excavate an escape tunnel towards the surface of the fruit ; this may also result in indirect damage, since fungi and bacteria may invade the fruit through the escape holes made by adult wasps. As a result some attacked fruits fail to develop, they darken, mummify and drop.1,2 Several authors have reported that wasps of the genus Bephratelloides are able to reduce fruit production by more than 70%.3 In some species of parasitic wasp, such as Apanteles (\Cotesia) liparidis, and Cardiochiles nigriceps Vier., females are responsible for the production of sex pheromone, which helps males to Ðnd them.4,5 However, very little is known about the biology and mating behaviour of B. pomorum. Therefore, we decided to study the mating behaviour of wild B. pomorum in order to understand the mechanisms involved in the reproductive behaviour of this species. 2 Materials and methods 2.1 Insects. Wild adult wasps of B. pomorum were obtained from infested soursop fruits from a commercial orchard in Maceio, Alagoas (north-east Brazil). The fruits were taken to the laboratory and kept in wooden cages until adult emergence. The adults were segregated by sex and kept in separate cages until used.

Abstract : The Annona seed borer, Bephratelloides pomorum (Hymenoptera : Eurytomidae), is the most important insect pest of soursop, Annona muricata L. The female lays eggs directly into the most recently formed seeds of developing fruit where the larvae remain feeding until pupation. When fully developed, the young wasps make a channel to emerge from the fruit, ready to copulate. Males are attracted to females and display a peculiar behaviour which consists of three steps : antennation, lateral bouncing and wing vibrations. Experiments carried out in semi-Ðeld and laboratory conditions showed that males also behave similarly in the presence of Ðlter paper impregnated with a hexane extract of the femaleÏs body, suggesting that female B. pomorum produce an attractant which enables males to Ðnd them. The hexane extracts of females, analysed by GC-MS, were shown to consist mainly of a mixture of straight- and branched-chain hydrocarbons and esters. ( 1998 Society of Chemical Industry

2.2 Field-cage experiments. The mating behaviour of B. pomorum was observed in a Ðeld-cage (2 m3) made from 20-mm nylon mesh. One potted host tree (height 1É6 m) was placed inside the Ðeld cage and two infested soursop fruits were hung from branches using cotton string. The fruits were replaced every three days. The average conditions of temperature and relative humidity inside the Ðeld-cage were 26(^2)¡C and 80(^10)%, respectively. The experiment was replicated 10 times. For each replicate, 20 newly emerged male B. pomorum were taken from the wooden holding cages, marked on the thorax with one or two small spots of a non-toxic coloured paint (without anaesthesia) and then released into the Ðeld-cage. Their behaviour was then monitored over 90 min. To observe the attraction of virgin male B. pomorum to virgin females, two plastic cages, made from recycled Coca-Cola} bottles, were used. One cage was painted with a black dye and its surface was perforated with small holes to resemble an attacked soursop fruit. The second cage was colourless and transparent and non-

Pestic. Sci., 54, 000È000 (1998)

* To whom correspondence should be addressed.

Laboratorio de Ecologia Qu• mica, Universidade Federal de Alagoas, BR 101 N, Km 14, Tabuleiro, 57072-970, Maceio, Alagoas, Brazil

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