Targeted Analyte Deconvolution and Detection of Piper longum Leaf Volatiles Using Two-Dimensional Gas Chromatography and Time-of-Flight Mass Spectrometry

Abstract

Piper longum L., known as long pepper, is an important species of the family Piperaceae due to its commercial and medicinal properties. However, its volatiles have only been analyzed by gas chromatography–mass spectrometry (GC–MS). The present study focused upon the precise characterization of Piper longum L. leaf volatiles for the first time by two-dimensional gas chromatography–time-of-flight mass spectrometry (GC × GC–TOF-MS). A total of 104 constituents accounting for 91.79% of the essential oil were identified due to the enhanced chromatographic separation and mass spectral deconvolution of GC × GC–TOF-MS, of which 20 constituents were reported first time. The identified constituents were categorized into alkanes (4.07%), alkenes (0.12%), aldehydes (0.52%), alcohols (6.87%), esters (2.40%), ether (0.26%), ketones (3.78%), monoterpene hydrocarbons (15.48%), oxygenated monoterpenes (4.21%), sesquiterpene hydrocarbons (22.68%), oxygenated sesquiterpenes (30.4%), diterpenes (0.75%), phenylpropanoids (0.14%), and fatty acids (0.15%). Among the classes, oxygenated sesquiterpenes were found to be the major group with E-nerolidol as the dominant compound (18.92 ± 0.02%), followed by β-pinene (5.41 ± 0.02%), α-pinene (4.44 ± 0.02%), and Z-caryophyllene (3.14 ± 0.03%). Additionally, GC × GC–TOF-MS separated 24 coeluting constituents which were unresolved using the one-dimensional GC column, hence justifying to be a noteworthy approach for analysing volatiles by two-dimensional GC system. The in-depth terpenic characterization may influence the overall quality of the oil as well as allow the future improvement of the species.