Comparative Fingerprint of Glucosinolates from Brassica Vegetables Using HATR/FT-MIR Spectroscopy

Abstract

Glucosinolates (β-thioglucoside-N-hydroxysulphates) are very important plant secondary metabolites containing a β-D-glucopyranose residue linked to a sulfur atom (i), or to a (Z)-Nhydroximinosulfate ester (ii) or a variable R group (iii) with different side-chain substituents which give their structural diversity.   The objective of the present research was to compare the fingerprint of 9 standard pure glucosinolates and Brassica vegetables extracts of broccoli, cauliflower and kohlrabi, cultivated in North-West of Romania, using the Fourier Transform Infrared Spectroscopy (FTIR). The FTIR fingerprint was recorded for both, desulpho - standards of glucosinolates (sinigrin, gluconapin, progoitrin, glucoiberin, glucoraphanin, glucotropaeolin and glucobrassicin) and intact glucosinolates (sinigrin and glucotropaeolin). The extraction of glucosinolates was made according to the EU official method (EEC Regulation N. 1864/90). The FTIR spectra for standards and Brassica dried extracts were recorded in the MIR region, from 4000 and 900 cm-1. The results obtained show that HATR/FT-MIR spectroscopy can be used as a fast method for the quantification of total glucosinolates considering the IR absorption at 800    cmor the region area of 750-900 cm-1, is the most suitable.  The HATR/FT-MIR is non-destructive, cheap and fast method to fingerprint, to predict and to quantify the glucosinolate composition of Brassica vegetables.