## 3 Results and Discussion
### Antioxidant Properties, Bioactive Content and Iron (II) Chelating Activity
DPPH and ABTS tests evaluate the in vitro anitracal activity, and FRAP assay the reducing potential of the extracts. Saffron stigmas presented stronger antioxidant capacity than the floral by-products, which could be related to the higher amounts of total flavonoids and crocus content since previous studies have demonstrated the significant antioxidant activity of flavonoids and crocins (2018). Nevertheless, saffron flowers, SFL1 and SFL2, showed a good antioxidant ability (by DPPH, ABTS, and FRAP) that could be related to their high polyphenols content. These results are similar to other studies that reported the antioxidant capacity of Indian and Iranian saffron stigmas ([PERSON], 2018; 2018), the potential antioxidant activity of commercial saffron powder from the large-scale Italian market ([PERSON] et al., 2018), and also to that of [PERSON] et al. (2018) in which it is revealed the strong antioxidant ability of saffron petals from China. Regarding the ability of the saffron extracts to chelate iron (II), the results are shown in Figure 1. Bivalent transition metal ions, such as iron, play an important role as catalysts of oxidative processes, participating in hydroxyl radical generation via the Fenton reaction ([PERSON] et al., 2018). Thus, excess metal ions could lead to the formation of free radicals generating high levels of oxidative stress, but these processes can be delayed by iron chelation. Apart from the ferric reducing power activity (FRAP) assay determination that indicated the reduction potential of Fe\({}^{3+}\) to Fe\({}^{2+}\), the iron (II) chelating activity of saffron stigmas and flowers was also studied. Figure 1: Iron (II) chelating activity of saffron floral-by products and saffron stigmas. The error bars represent the standard deviation and the different lowercase letters indicate statistically significant differences at \(p\leq 0.05\) for each sample (\(n=3\)). SFL1, SFL2: Saffron floral by-products from two different producers. Saffron stigmas presented a good chelating activity, around 60% of inhibition, with the highest for the Greek saffron (Figure 1). This ability could be due to their flavonoid content since previous research demonstrated that these bioactive compounds have the capacity to neutralize reactive radicals and sequestrate metal ions, suppressing Fenton reactions [28]. Saffron flowers showed a low iron chelating activity (less than 20% of inhibition), with the capacity of SFL2 significantly higher than SFL1 (Figure 1). This fact might be related to the anthocyanins content of SFL2 (Table 1). These results were similar to those reported by [PERSON] et al. [29], indicating that saffron petals from Spain had very low chelating activity. Therefore, the chelating activity of Fe\({}^{2+}\) and antioxidant capacity that presented saffron and its floral by-products could prevent oxidative damage, protecting against oxidative stress. These abilities may be linked to their bioactive compounds content that were located differently on the flower; stigmas had carotenoids and flavonoids, and the rest of the flower presented anthocyanins and other polyphenolic compounds.