New insights on the chemical composition of essential oils from Vietnamese Piper umbellatum L. investigated by combination of chromatographic and spectroscopic techniques

The compositions of leaf and stem essential oils from Vietnamese Piper umbellatum L. has been investigated by combination of chromatographic [GC(RI), GC-MS, CC] and spectroscopic techniques (GC-MS, C-13 NMR). Thirty-nine compounds have been identified, they accounted for 99.7% and 99.6%, respectively, of the whole compositions, dominated by safrole (76.2 and 66.0%). Stem oil contained fair amounts of (2E,4E)-decadienoic acid methyl ester, (2E,4E,6E)-decatrienoic acid methyl ester and (2E,4E)-N-isobutyl-2,4-decadienamide, reported for the first time in P. umbellatum essential oils and rarely found in the plant kingdom. The stereochemistry of all the double bonds was ascertained by using C-13 NMR data.