UPLC-ESI-TOF MS Profiling Discriminates Biomarkers in Authentic and Adulterated Italian Samples of Saffron (Crocus sativus L.)

Abstract

Italian saffron (Crocus sativus L.) is gaining visibility due to its high quality and difference in growing area. In this study, the metabolite composition and quality of Italian saffron samples purchased from local producers and supermarkets were investigated using an untargeted metabolomics approach using UPLC-ESI-TOF MS with simultaneous acquisition of low- and high-collision energy mass spectrometry (MS^e). Unsupervised statistical method (PCA) highlighted significant differences in the metabolomes, even if not related to the geographical origin. OPLS-DA revealed 9(S)-,10-(S)-,13-(S)-tri-hydroxy-11-(E)-octadecenoic acid as the most decisive compound to distinguish supermarket saffron, while oxidized crocins represented the most valuable markers to further describe the quality of saffron, even in locally produced samples. Known adulterations with paprika and turmeric were detected at a limit of 10%, and the increasing signals of cyclocurcumin was a significant biomarker for turmeric contamination. The results were underlined with conventional and kinetic antioxidant assays.

Figure 1

Score plot (comp. 1 vs comp. 2) of UPLC-ESI-TOF MS full scan analysis (50–1200 Da, ESI^–, high-resolution mode) of saffron samples (three technical replicates, two extraction replicates, and two biological replicates per samples). Letters A-N refer to Table 1.

Figure 2

S-Plot of supermarket samples (I, J, K) and D (–1) versus all the others (A, B, C, E, F, G, H, L, M, N; +1).

Figure 3

Chemical structures for compounds 1–26. 1–4, 6–12, and 14–23 are proposed based on MS data or/and literature data, and the stated stereochemistries are tentatively deduced in accordance to the known compounds in the literature.

Figure 3

Chemical structures for compounds 1–26. 1–4, 6–12, and 14–23 are proposed based on MS data or/and literature data, and the stated stereochemistries are tentatively deduced in accordance to the known compounds in the literature.

Figure 4

Extracted ion chromatogram of crocin 1 (a), crocin 2 (b), and crocin 3 (c) isomers in saffron sample G, and reference compounds crocin 1 (25), 2 (13), and 3 (26) (d).

Figure 5

High-collision energy (MS^e) fragmentation spectrum of compound 14.

Figure 6

Score plot (comp 1 vs comp 2) of total phenol content (TPC), total crocin content, and kinetic parameters for the antioxidant activity.