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

Abstract 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 .