Identification and Enantiodifferentiation of C13 Norisoprenoid Degradation Products of Glycosidically Bound 3-Hydroxy-α-ionol from Stinging Nettle (Urtica dioica L.)

Article abstract of DOI:10.1021/jf00054a044

Acid-catalyzed degradation (simultaneous distillation-extraction; pH 2.5) of glycosidically bound 3-hydroxy-α-ionol from stinging nettle (Urtica dioica L.) yielded 2,2,6-trimethyl-7-methylenebicyclo<4.3.0>nona-4,8-diene and 2,2,6,7-tetramethylbicyclo<4.3.0>nona-4,7,9-triene as well as 1-(2-butenylidene)-2,6,6-trimethylcyclohexa-2.4-diene(1),1-(2-butenylidene)-6,6-dimethyl-2-methylenecyclohex-3-ene (2),and isomeric 4-(2,6,6-trimethylcyclohexa-2,4-dien-1-yl)but-3-en-2-ol(2,3-didehydro-α-ionol) (3a-d) and 4-(6,6-dimethyl-2-methylenecyclohex-3-en-1-yl)but-3-en-2-ol(3,4-didehydro-γ-ionol) (4a-d), which were identified by comparison of their chromatographic and spectral (MS; vapor phase FTIR) data with those of synthesized reference compounds.Configuration of the butenylidene chain of 1 and 2 was established by NOE experiments.The absolute configuration of the stereoisomers of 3 and 4 was elucidated using optically pure reference compounds.Enantiodifferentiation carried out by on-line coupled multidimensional gas chromatography-mass spectrometry revealed the occurrence of 1'R,2R and 1'R,2S diastereomers (3a/3c and 4a/4c) in stinging nettle. Keywords: 1-(2-Butenylidene)-2,6,6-trimethylcyclohexa-2,4-diene; 1-(2-butylidene)-6,6-dimethyl-2-methylenecyclohex-3-ene; 2,3-didehydro-α-ionol; 3,4-didehydro-γ-ionol; enantiodifferentiation; 3-hydroxy-α-ionol; stinging nettle