## 3 Results and Discussion
### Antioxidant Activity  
Antioxidant properties are a frequently evaluated parameter of foodstuff. It is assumed that eating foods rich in antioxidants can help to protect the body from the harmful effects of free radicals. A frequently used method to determine general antioxidant properties is the ability to reduce iron ions (FRAP). Numerous studies indicate that mushrooms are a good source of antioxidant substances, which is also confirmed by these results. As shown in Figure 4a, the values of the FRAP parameter for the whole fruiting bodies ranged from 8.16 \(\pm\) 0.11 umoles/g (_P. nameko_) to 25.33 \(\pm\) 0.86 umoles/g (the white _A. bisporus_). High FRAP values of button mushrooms have been noticed previously. [PERSON] et al. [21] reported the FRAP capacity in the white _A. bisporus_ at \(\sim\)30 umoles/g. Other authors reported exceptionally high FRAP activity in _A. bisporus_ methanolic extracts in comparison to other cultivated or wild-growing species [34; 35]. Figure 4: The FRAP antioxidant activity of the extracts from caps, stems and whole fruiting bodies, expressed per fruiting body dry weight (**a**) and per extract dry weight (**b**); Abw—_A. bisporus_ (white), Abb—_A. bisporus_ (brown), Le—_L.odes_, Pr—_P. nameko_, Pe—_P. eryugii_, Po—_P. ostreatus_. Mean values (\(n\) = 3) with different lowercase letters show significant differences among the parts of mushrooms belonging to the same species. Mean values with different capital letters indicate significant differences among the same parts belonging to various species (\(p\) < 0.05, Tukey’s test). The caps exhibited higher FRAP antioxidant activity compared to the stems in all the investigated species except for _P. nameko_, where the stems displayed slightly higher antioxidant capacity. Similar to the content of phenolics, the most significant difference between the parts was noticed in _P. ostreatus_ (the activity of the caps was approximately three times higher compared to the stems). When the FRAP values were calculated per one gram of the dry extract (Figure 4b), it appeared that the strongest antioxidant capacity is displayed by the extracts obtained from _P. ostreatus_ caps (97.38 \(\pm\) 5.40 \(\upmu\)moles/g), followed by the caps of _A. bisporus_ brown and white (67.00 \(\pm\) 1.15 \(\upmu\)moles/g and 64.75 \(\pm\) 1.43 \(\upmu\)moles/g, respectively). On the contrary, the weakest activity levels were reported in _P. ostreatus_ stems (15.09 \(\pm\) 0.53 \(\upmu\)moles/g). In most of the analyzed species the extracts from the stems displayed significantly lower antioxidant capacities. However, in the cases of _A. bisporus_ (white) and _P. erggii_, the differences were not so evident. These results support previous findings by [36], who noticed that methanolic extracts from _L. edodes_ stems displayed lower activities compared to the caps. Moreover, [26] compared the FRAP values of the methanolic extracts obtained from the different parts of _A. bisporus_. They observed insubstantial differences between the stems and the caps, despite the fact that the caps contained significantly higher concentration of the total phenolics (-21 mg/g and 15 mg/g for the caps and the stems, respectively). It is strongly recommended to use more than one antioxidant assay to evaluate properties of foodstuff, as various methods may produce quite different results. The reason for this is that these assays differ in their mechanisms of reaction and specificity [37]. The scavenging of DPPH radicals is a very common method which is used to determine the antioxidant capacity of mushroom-derived extracts. The activity range of whole mushrooms varied, as shown in Figure 5a, from 4.17 \(\pm\) 0.12 \(\upmu\)moles/g (_P. nameko_) to 8.85 \(\pm\) 0.10 \(\upmu\)moles/g (the brown _A. bisporus_). Interestingly, there was no statistically important difference between _A. bisporus_ white and brown, although the brown contained a \(\sim\)20% higher amount of total phenolics and a \(\sim\)12% higher amount of total flavonoids. In this study _P.