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Chemical analysis of the female sex pheromone in Palpita nigropunctalis (Lepidoptera: Crambidae)

Yan, Qi, Fujino, Aguri, Naka, Hideshi, Dong, Shuang-Lin, Ando, Tetsu
Journal of Asia-Pacific entomology 2018 v.21 no.4 pp. 1283-1288
Crambidae, Oleaceae, absorption, acetates, aldehydes, chemical analysis, chemical bonding, dimethyl disulfide, electroantennography, females, ions, males, moieties, pests, pheromone glands, sex pheromones, spectrometers, spectrophotometers
The lilac pyralid, Palpita nigropunctalis Bremer (Lepidoptera: Crambidae), is a common pest of Oleaceae plants. A crude extract of the female sex pheromone glands was examined by gas chromatography-electroantennogram detection (GC-EAD) and GC coupled to a mass spectrometer (GC/MS). The GC-EAD analysis revealed three EAG-active components (I–III) in a ratio of 1:0.2:0.01 (I: II: III). GC/MS analysis successfully recorded the mass spectra of I and II. For I, ions at m/z 238 (M+) and 220 ([M-18]+) indicated the structure of a monoenyl aldehyde with a 16-carbon chain. For II, M+ was not detected, but ions at m/z 222 ([M-60]+) and 61 ([AcOH+1]+) suggested that II was a monoenyl acetate with a 16-carbon chain. Further GC/MS analysis of the extract treated with dimethyl disulfide revealed that the double bonds in both I and II are located at the same position of 11th-carbon. In addition, the pheromone extract was examined by GC/Fourier transform-infrared spectrophotometer (GC/FT-IR). An IR spectrum of I showed characteristic absorption at 1716 and 966 cm−1, indicating a formyl group and E configuration of the double bond, respectively. In the case of II, absorption at 1745 and 968 cm−1 indicated an ester carbonyl and E configuration, respectively. Taken together and by comparison with authentic standards, I and II were confirmed as (E)-11-hexadecenal and (E)-11-hexadecenyl acetate, respectively; while III was speculated as (E)-11-hexadecen-1-ol. The synthetic I, II and III all coincided well with those of the natural components in chemical data, and elicited strong electroantennographic activity in male P. nigropunctalis.