The combined gas chromatography - mass spectrometry provides an excellent method for the study of the secretions of insects

Notizen 935

The Defensive Secretion of Aspavia brunna (Schout) (Hetetoptera: Pentatomidae) M. I. Akpata and T. 0. Olagbemiro*

Faculty of Science, Department of Chemistry Bayero University, P.M.B. 3011, Kano, Nigeria Z. Naturforsch. 37 B, 935-936 (1982);

received October 19, 1981/February 25, 1982 Heteroptera, Pentatomidae, Scent Volatiles, a-Terpeneol, Pheromonal

The pungent odours emitted by true bugs when disturbed have captured the attention of numerous students of the Heteroptera. Studies of the chemical composition of the secretion of these stink bugs have shown the presence of alkanes, alkenyl acetates, alcohols and un- saturated aldehydes [1-3]. Most of these chemi- cals are employed as chemical warfare against the onslaught of microbial, vertebrate and in- vertebrate attackers [4], We herein report the chemical investigation of a previously unstudied secretion of a pentatomid bug, Aspavia brunna.

The combined gas chromatography - mass spectrometry provides an excellent method for the study of the secretions of insects. We have utilized this technique and our results are sum- marized below.

Abbreviations: R.T., Retention time; R. A., Relative amount ( % ) ; M.W., Molecular weight; CI, Chemical ionization; EI, Electron impact: m/z(^0/0), mass/charge ( % relative peak intensity).

From the mass spectral analysis of the extracts of the scent volatiles of Aspavia brunna we obtained the following spectral data:

Peak 1: (R.T., 8.55; R. A., 16.65), M.W., 98.

mjz CH4CI 99 (M-j- 1, 100), 85(8).

mjz El 98 (M+, 15), 97(7), 83(15), 70(40), 69(75).

55(85), 41(100).

Proposed identity: trans hex-2-enal.

Peak 2: (R.T., 9.60; R.A., 8.25), M.W., 102.

mjz CH4CI 101 (M—1,5), 84(100).

mjz El 84 (M+-18.30). 73(10). 69(60). 55(50), 56(100), 43(75).

Proposed identity: 1-hexanol.

Peak 3: (R.T., 10.30; R.A., 4.65), M.W., 154.

mjz CH4CI 153 (M—1,5), 137(100), 121(15).

mjz EI 136 (M+-18, 8). 121(65). 105(10), 93(100), 85(40), 71(35), 59(95), 41(50).

Proposed identity: a-terpeneol.

* Reprint requests to Dr. T. O. Olagbemiro.

0340-5087/82/0700-0935/5 01.00/0

Peak 4: (R.T., 12.70; R.A., 6.30), M.M., 126.

mjz CH4CI 127 (M+l, 50), 109(100), 85(30).

mjz EI 126 (M+, 10). 125(7), 110(20). 108(18). 70(80).

55(85), 41(100).

Proposed identity: trans oct-2-enal.

Peak 5: (R.T., 13.50: R.A., 3.10), M.W., 154.

mjz CH4CI 153 (M—1, 25), 125(43), 69(57), 55(65).

mjz EI 154 (M+, 12), 125(7), 83(35), 69(45). 57(65), 55(70), 43(85), 41(100).

Proposed identity: 1-undecene.

Peak 6: (R.T.. 14.65; R. A., 37.45), M.W., 168.

mjz CH4CI 167 (M—1, 15). 139(25), 111(40), 55(80).

mjz EI 168 (M+, 8). 139(5), 111(8), 97(25), 83(45).

69(40), 57(55), 55(70), 43(85), 41(100).

Proposed identity: 1-dodecene.

Peak 7: (R.T., 16.85; R.A., 18.40), M.W., 184.

mjz CH4CI183 (M—1, 30), 141(12), 112(30), 85(100).

mjz EI 184 (M+, 10), 101(5), 99(8), 85(40), 71(65), 57(100), 43(75).

Proposed identity: tridecane.

Peak 8: (R.T., 20.15; R.A., 5.20), M.W., 288.

mjz CH4CI 289 (M+l, 15), 260(20), 245(25), 200 (100).

mjz EI 288 (M+, 10). 248(15), 210(35), 198(14), 180(25), 175(10), 168(14), 140(12). 126(30), 110(85), 95(60), 83(45), 71(100).

Proposed identity: unknown.

Each compound identified above matched spectra on file in the computerized mass spectral search system, and were varified by coinjection of the extracts with authentic standards.

Attempts to provide a chemical structure for the compound responsible for the gas-chromatographic peak 8 was unsuccessful. Peak 3 was proposed as the monoterpene a-terpeneol since the mass spectrum obtained fits this proposed structures in both the Cl and EI modes. Furthermore, when authentic sam- ples of a-terpeneol and the extracts were coinjected, their retention times were unseparatable, as only a single peak was obtained.

In general, our chemical analyses of these previously unstudied scent volatiles of Aspavia brunna (Heteroptera: pentatomidae) revealed some interesting divergence from those of the already reported Heteropteras. £ra»s-2-Hexenal, trans-oct- 2-enal and tridecane have been identified in some pentatomid bugs [5, 6], However, monoterpenes in general have not been reported from the penta- tomidae, although they have been observed in coreids [8], The presence of unsaturated compounds, dodecene (major component) and undecene is particularly striking as these have never been observed in the pentatomids. The unsaturated aldehydes, £ra/iS-2-hexenal and £ra/i<s-oct-2-enal together with tridecane are known to serve as

936 Notizen defensive substances in some Heteropteras [4, 7, 9].

It is suggested that they serve the same pheromonal role in Aspavia brunna.

Materials and 3Iethods

Insects. The insects 10,000 of them, were collected on an agricultural farm land at Kadawa, Kano State, Nigeria and were killed by immersion in chromatoquality dichloromethane and stored at

—20 °C until the analyses. The metathorax was removed and extracted with a fresh portion of di- chloromethane.

Chemical analysis. A concentrated sample of this extract was examined first, on the Varian 1400 gas chromatography equiped with a flame ionization detector. The 6ft. glass column (i.d. 2 mm) was packed with 3% OV 225 on a 60-80 mesh Gas Chrom Q. Analyses were carried out under two

different conditions (1) oven temperature at 10°/min from 80 to 220 °C with nitrogen flow rate at 30 ml/min (2) oven temperature from 80 to 200 °C with nitrogen flow rate at 20 ml/min. A final analysis of the volatile extract was performed on a Finnigan 3200 quadrupole mass spectrometer equiped with a printonix data plotter. The gas Chromatograph oven temperature was programmed at 4 °C/min from 80-200 °C using an OV 225 packed column. Chemi- cal ionization (CI) with methane as the reagent gas, source, temperature 240 °C, and electron impact (EI) with source temperature 260 °C modes were employed in the analysis of the scent volatiles.

We thank the Bayero University Research and Higher Degrees Committee for their financial support, the Chemistry Department University of Jos, Plateau State, Nigeria, and the Chemistry Department Uni- versity College, Cardiff Wales, U.K., for the gc-ms analysis of samples.

[1] J. Weatherston, Quart. Rev. 21, 287 (1967).

[2] J. Weatherston and J. E. Percy, Arthropod defensive secretions in M. Beroz (ed.): Chemicals Controlling Insects Behavious, Academic Press, New York 1970.

[3] H. Schildknecht, Angew. Chem. Int. Ed. 9, 1 (1970).

[4] H. Remold, Nature 198, 764 (1963).

[5] A. R. Gilby and D. F. Waterhouse, Proc. R. Soc.

London, Ser. B 162, 105 (1965).

[6] T. Isliiwatari, Appl. Entomol. Zool. 9, 153 (1974).

[7] D. H. Calam and G. C. Scott, J. Insect Physiol.

15, 1695 (1969).

[8] J. R. Aldrich and T. R. Yonke, Ann. Entomol.

Soc. Am. 68, 955 (1975).

[9] O. P. Kathuria, W. V. Brown, and A. R. Gilby, Indian J. Ent, 36, 31 (1974).

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