Determination of l- and d-amino acids in smokeless tobacco products and tobacco

Abstract

Quantities of free l- and d-amino acids were determined by GC-SIM-MS in 25 European snuff tobaccos (from Germany, England and Sweden) and eight chewing tobaccos (from the Philippines, Africa and Denmark) and compared to those of cigar, cigarillo, and freshly harvested tobacco leaves of cultivars of Nicotiana tabacum L. Amino acids were isolated from tobacco samples by treatment with 70% aqueous methanol and purified by a cation exchanger. Next they were converted into their N( O)-pentafluoropropionylamino acid-(2)-propyl esters, and enantiomers separated and quantified by GC-SIM-MS on a Chirasil ®- l-Val capillary column. Among l-amino acids the most abundant were Pro, Asx and Glx in the low milligram range (about 2–6 mg/g) whereas the other l-amino acids were in the submilligram range. Though native tobacco leaves contained low amounts of few d-AAs (0.2–1.9%), all processed tobacco samples had d-amino acids in varying amounts and patterns. The d-enantiomers of Ala, Asx and Glx were detected in all samples approaching 34.0% d-Ala, 13.8% d-Asx, and 16.1% d-Glx in different samples. Large quantities of other d-amino acids were also detected in tobaccos approaching 32.2% d-Leu, 25.8% d-Phe and 18.0% d-Thr in various samples. Lower amounts of the d-enantiomers of d-Val, d-Ile, and d-Pro could also be determined in certain tobaccos. It is assumed that d-amino acids are generated from fructose- l-amino acids (Amadori rearrangement products) which are formed in the course of the Maillard reaction.