Volatile Constituents from the Flowers of Japanese Honeysuckle (Lonicera japonica)

The flowers of Japanese honeysuckle ( Lonicera japonica ) have been shown by field observation to be attractive to a variety of economically important adult lepidoptera. The present study was performed to identify and quantify the volatile chemical constituents of L . japonica flowers, at different stages of development, to provide a basis for systematic evaluation of insect attraction. Methylene chloride extracts of flowers obtained at three stages of development (freshly opened, overnight, and 24 h) were subjected to vacuum-steam distillation/hexane extraction using a modified Likens−Nickerson apparatus. Volatile constituents were identified and quantitated using gas capillary chromatography/mass spectrometry. Twenty-seven compounds, 13 of which have not been reported in Lonicera spp. flowers, were identified among the three developmental stages. Germacrene D was a major component at all stages; linalool and α-farnesene appeared in high concentrations in fresh and 24 h flowers but were greatly reduced in overnight flowers. The latter, however, contained elevated levels of phenylpropanoid biosynthesized compounds, suggesting a marked diurnal influence on the biosynthesis of volatile flower constituents involving two modes of action: phenylpropanoid and lipoxygenase derivation.