Antioxidant Activity, Total Phenolic and Flavonoid Contents in Floral Saffron Bio-Residues

Saffron spices are composed of dehydrated stigmas of Crocus sativus L. A large amount of bio-residues (stamens, tepals, and stigmas) is generated during the production of this spice (similar to 92 g of bio-residues per 100 g of flowers). These bio-residues are usually discarded losing the chance to obtain interesting bioactive compounds from them. In this work, we use the saffron bio-residues as possible source of natural bioactive compounds. Different extraction conditions were applied obtaining hydrophilic and lipophilic components. The antioxidant activity of the bioactive compounds in the different conditions were analysed using the ABTS method developed by our team. Furthermore, the total content of phenolic compounds and flavonoids present in the bio-residues were estimated. We demonstrated that bio-residues contain a high amount of both phenolic and flavonoid compounds with a strong antioxidant potential effect. Moreover, we compared the antioxidant activities of saffron bio-residues (obtained from stamens, tepals, and stigmas). The extraction was made at two different pH (4.5 and 7.5) and measured (antioxidant activity, flavonoid and phenol content) at pH 7.5. Another extraction done at pH 7.5 measured antioxidant activity, flavonoid and phenol content at time 0 (t = 0 h) and after 24 h (t = 24 h) at pH 4.5 and 7.5. We point out that bioresidues contain antioxidant activity (up to 8.42 mu moles Trolox/100 g DW), total phenols (up to 111.91 mu moles EG/100 g DW) and total flavonoids (up to 109.25 mu moles QE/100 g DW) as bioactive compounds. The applicability of bio-residues as additives is promising, both in the pharmaceutical and in the food industry as nutraceuticals and phytogenics. The variability in pH and the colour originating from it must be taken into account.