Chemical Constituents and Acetylcholinesterase Inhibition of Senecio ventanensis Cabrera (Asteraceae)

Chemical constituents and acetylcholinesterase inhibition was investigated in both essential oil and dichloromethane subextract obtained from the aerial parts of Senecio ventanensis, an endemic Asteraceae. The chemical composition of the oil was determined by GC and GC-MS. The major constituents were a -terpinene (12.2%), limonene (11.9%), -humulene (10.5%), sabinene (9.1%), terpinolene (8.8%), p-cymene (8.1%) and a -ocimene (7.3%). The bioassay guided isolation of the constituents of the active dichloromethane subextract (IC 50 = 361.6 µg/mL) led us to the isolation of two diastereoisomers of a sesquiterpene endoperoxide 3,6-epidioxy-1,10-bisaboladiene (1 and 2), reported here for the first time in S. ventanensis. The identification was achieved by comprehensive analyses of its 1H and 13C NMR spectroscopic data (including 2D experiments) and mass spectrometric data. Their absolute configuration is proposed on the basis of AM1 calculations and NOESY experiments. This is the first time that compounds 1 and 2 have been separated as well as the first phytochemical investigation of S. ventanensis.