Investigation on secondary metabolite content and antioxidant activity of commercial saffron powder

The secondary metabolites and the antioxidant properties of twelve commercial saffron powder samples, purchased from Italian large-scale market, were studied. An HPLC-DAD method was applied to determine the content of trans-4-digentiobioside crocetin ester (trans-crocin-4), picrocrocin, and safranal, while the antioxidant activity of methanolic extracts of saffron samples was tested using two in vitro assays, DPPH and ABTS. The samples were also subjected to alkaline hydrolysis before testing. The content of trans-crocin-4 ranged from 1.7 to 7.5/100 g, while picrocrocin content varied from 2.6 to 6.7/100 g. Using DPPH test, all saffron samples showed very low radical scavenging activity, while higher values were observed after hydrolysis. As regards ABTS assay, saffron samples exhibited higher antioxidant activity against radical than the respective hydrolyzed. Interestingly, correlations between DPPH values of hydrolyzed samples and ABTS values of methanolic extracts were obtained. Moreover, a significant correlation (R-2 = 0.5732) between ABTS values and transcrocin-4 content of saffron samples was observed. The obtained results contribute to the characterization of saffron powder, the most used and economic but also the less studied form of saffron.