## 2 Results and Discussion
### Antioxidant Activity  
In the last decades, oxidative stress has been recognized to play a critical role in the pathogenesis of several diseases. This has significantly increased research studies aimed at discovering new plant sources of antioxidants. The _Brassicaceae_ family encloses many plant species that are potential sources of antioxidant compounds, including some belonging to the _Matthiola_ genus, as also demonstrated in recent studies on _M. incana_ infraspecific taxa carried out by our research team [2,18,19,20]. In this work, the antioxidant properties of the extracts of _M. fruciculosa_ subsp. _fruticulosa_ and subsp. _coronopifolia_ were established using three in vitro tests to evaluate the different mechanisms through which the diverse antioxidant compounds contained in the phytocomplexes could exert their effect: DPPH assay, based on the hydrogen atom transfer (HAT) and electron transfer (ET) mechanisms; reducing power, an electron transfer (ET)-based assay; and ferrous ion (Fe\({}^{2+}\)) chelating activity assay. Figure 3A shows the results of the DPPH assay, utilized to determine the free scavenging ability of the extracts. Compared with the reference standard BHT, both extracts displayed lower activity in the range of concentrations tested, which increased with increasing dose. The extract of _M. frucitulosa_ subsp. _fruticulosa_ exhibited the best scavenging activity, reaching about 70% inhibition of the DPPH radical at the highest concentration tested. From the comparison of the calculated IC\({}_{50}\) values, it was evidenced that the radical scavenging ability of the _M. frucitulosa_ subsp. _fruticulosa_ extract, showing an IC\({}_{50}\) of 1.25 \(\pm\) 0.02 mg/mL, was approximately 2.3-fold higher than that of the subsp. _coronopifolia_ extract (IC\({}_{50}\) = 2.86 \(\pm\) 0.05 mg/mL). Comparing the free radical scavenging activity of the _M. frucitulosa_ subsp. _fruticulosa_ extract with that highlighted in other _Matthiola_ species, the result showed an activity higher than that of the hydroalcoholic extracts (80% MeOH) of the aerial parts from the _Matthiola incana_ infraspecific taxa endemic to Sicily, whose antioxidant properties had previously been investigated under the same experimental conditions, namely, _M. incana_ subsp. _incana_, IC\({}_{50}\) = 2.32 \(\pm\) 0.24 mg/mL; subsp. _rupestris_, IC\({}_{50}\) = 1.73 \(\pm\) 0.02 mg/mL and 2.60 \(\pm\) 0.01 mg/mL; and subsp. _pulbrella_, IC\({}_{50}\) = 3.69 \(\pm\) 0.14 mg/mL [2,18]. On the other hand, [PERSON] et al. [20] reported a lower IC\({}_{50}\) value (0.49 mg/mL) for a hydroalcoholic extract (80% MeOH) obtained by maceration from the aerial parts of _M. longipetala_ subsp. _longipetala_ collected in Libya. The results of the evaluation of the reducing power of the extracts of the two subspecies of _M. frucitulosa_, determined through the Fe\({}^{3+}\)-Fe\({}^{2+}\) transformation method, showed that both extracts displayed mild activity compared with the standard BHT. This result agrees with those previously reported for the extracts of the aerial parts from the _M. incana_ infraspecific taxa [2,18]. As shown in Figure 3B, the extracts exhibited similar reducing power, dose dependent, although the calculated ASE/mL values indicated greater reducing efficacy for the extract of subsp. _coronopifolia_ (18.61 \(\pm\) 0.06 mg/mL) than that of subsp. _fruticulosa_ (38.17 \(\pm\) 1.14 mg/mL). Both extracts are less active than that of _M. incana_ subsp. _incana_ (ASE/mL = 12.28 \(\pm\) 0.42 mg/mL), which showed the best reducing power among the infraspecific taxa of _M. incana_[2,18]. In the Fe\({}^{2+}\) chelating activity assay, performed by evaluating the inhibiting effect on the Fe\({}^{2+}\)-ferrozine complex formation, both extracts of the two subspecies of _M. frucitulosa_ showed good chelating properties, dose dependent, although lower than those of the reference standard EDTA (Figure 3C). Contrary to what has been observed in the other antioxidant assays, the extract of _M. frucitulosa_ subsp.