Classification of Greek Mentha pulegium L. (Pennyroyal) Samples, According to Geographical Location by Fourier Transform Infrared Spectroscopy

Introduction - Mentha pulegium L. (pennyroyal) is one of the four most commercially important Mentha species, even it is not a cultivated plant. It can be abundantly located in the Iberian Peninsula and North African countries. In Greece it grows in the wild and it is scattered all over the country. Pennyroyal is best known for its essential oil, with Spain and Morocco being the largest producers in the world. Mid-infrared spectroscopy has been applied to determine the origin of various samples. Objectives - In this work Fourier transform infrared spectroscopy (FT-IR) combined with canonical discriminant analysis has been applied to distinguish 70 Greek pennyroyal samples according to their collection areas. Material and methods - Pennyroyal nonpolar organic extracts were prepared using ultrasound-assisted solvent extraction. The spectra of the extracts were recorded in the range of 4000-400 cm(-1) and the best discrimination was achieved in the spectral region 1720-1650 cm(-1). Results - Spectral features for the discrimination of pennyroyal samples among the different collection areas occur primarily in the carbonyl region and are correlated with the main volatile constituents of the extracts (menthone, isomenthone, pulegone, piperitone). All areas were easily differentiated by canonical discriminant analysis. The percentages of correct classification and validation were 94.3 and 90.0%, respectively. Conclusion - The combination of FT-IR spectroscopy and multivariate analysis provides a rapid and ambient method to discriminate pennyroyal samples in terms of geographical origin. Copyright (C) 2011 John Wiley & Sons, Ltd.