Is Linalyl Anthranilate Indeed Found In Plant Samples? GC-MS Misidentifications in the Scientific Literature.

Abstract

Linalyl anthranilate (LNA) has been identified in a number of plant extracts and essential oils by various authors using gas chromatography-mass spectrometry (GC-MS). However, the reported retention behavior of LNA in these studies is inconsistent with the retention data provided in the NIST database. Therefore, the objective of this study was to determine whether the reports of LNA were the result of misidentifications in GC-MS analyses or if the linear NIST retention index was inaccurate. To accomplish this, linalyl anthranilate was synthesized in a two-step procedure, and the resulting product was authenticated using nuclear magnetic resonance (NMR) and GC-MS analyses. This is a new synthetic route to linalyl anthranilate. Subsequently, retention indices for linalyl anthranilate were determined on three commonly used GC phases: polydimethylsiloxane, 5% diphenyl-95% polydimethylsiloxane, and polyethylene glycol. The study confirmed the accuracy of the NIST retention data, establishing the linear retention index data for LNA on a semi-nonpolar GC column as 2051. However, LNA reported in the literature by various authors exhibited a retention index in the elution window of approximately 1000-1400, strongly suggesting that these reports were the result of GC-MS misidentifications. A review of all reported occurrences of LNA in natural samples found no credible evidence of its presence. In many cases, it appears to be a misidentification of linalyl acetate caused by the occurrence of an erroneous spectrum in the older versions of the NIST mass spectra database.