Chemical investigation of the bitter substances of the fruit of Lonicera caerulea

Abstract

Esters of malic and citric acids have been isolated from an ethyl acetate fraction of an ethanolic extraction ofLonicera caerulea L.: dibutyl malate (I), 4-butyl 1-methyl malate (II), 1-butyl 4-methyl malate (III), tributyl citrate (IV), 1,5-dibutyl citrate (V), 1,1′-dibutyl citrate (VI), 1,5-dibutyl 1′-methyl citrate (VII), 1,1′-dibutyl 5-methyl citrate (VIII), 1-butyl citrate (IX), 1′-butyl citrate (X), 1′-butyl 1,5-dimethyl citrate (XI), and 1-butyl 1′,5-dimethyl citrate (XII). Compounds (I-IV, VII, VIII, XI, and XII) had a bitter taste and were the main components of the bitter substances of the fruit ofLonicera caerulea. The structures of compounds (I-XII) were established on the basis of their1H and13C NMR spectra, by FAB mass spectrometry and chromato-mass spectrometry.