ATR-FTIR spectroscopy combined with DNA barcoding and GC-MS to assess the quality and purity of saffron (Crocus sativus L.)

Abstract

Fourier transform infrared spectra of saffron (Crocus sativus L.) samples were acquired using attenuated total reflectance (ATR-FTIR). The main objective of the study was to determine the chemical composition of 11 samples of saffron collected from different areas in Morocco using the chemometric analysis of ATR-FTIR fingerprints and identifying the adulterated saffron among samples bought from local markets in different countries (Spain, Iran, and Morocco). The the authenticity and the purity of saffron samples was validated through a molecular analysis (DNA barcoding coupled to sequencing) and chromatographic analysis GC-MS. The results of ATR-FTIR showed vibration intensities of six distinct fingerprint regions displaying statistically significant differences. The spectrum of the sample from Timjicht (Taznakht) showed typical bands due to the vibration in 3000–2800 cm-1 (the richest in carbohydrates, lipids, and amino acids) and 1800–1725 cm-1 region (the richest in carbonyl and ester groups) and was classified a single subset in samples scatter plot. Then samples from Boulmane (S2), Ain Leuh (S3), Taliouine (S6), and Taznakht (S7-S8) were classified close to each other, which indicates the similarity in their vibration intensities mainly in the region of carbohydrates, lipids, amino acids, and esters. Similarities in terms of proteins and hydroxyl groups were revealed between the samples from El Mers (S11) and Taliouine (S1). Finally, the last sub-group contained samples from Ourika, Azilal and Ain Atia, which showed low composition in all components. Furthermore, to detect adulterated saffron from samples of unknown origin, a comparison of the ATR-FTIR spectra were carried out with spectra of pure saffron and results showed that the peaks at 1706, 1732, and 1225 cm-1 (linked to crocin which are present primarily in saffron) were absent in one sample (SI). Interestingly, the use of another plant species named Arrhenatherum elatius as materiel for saffron adulteration was confirmed by the molecular study (DNA barcoding) and chromatographic analysis GC-MS