## 3 Results and Discussion
### Phenolic Acids Profile  
Several phenolic acids or their derivatives were detected in the mushrooms' fruiting bodies. They can be seen in Figure 3, which contains an exemplary chromatogram obtained from _P. nameko_ caps. As can be seen from Table 4, which shows the comparison of the whole fruiting bodies, the richest in 3,4-DHBA were _P. eryngii > P. ostreatus > P. nameko_. Significant amounts of caffeic acid was observed in _L. edodes_, _P. nameko_ and A. bisporus (white). The content of syringic acid varied from 0.09 \(\pm\) 0.01 \(\mathrm{\SIUnitSymbolMicro g}\) (_P. eryngii_) to 1.53 \(\pm\) 0.02 \(\mathrm{\SIUnitSymbolMicro g}\)/g (_P. nameko_). With regard to _p_-comamaric acid, the richest sources were the fruiting bodies of _P. nameko_ (3.00 \(\pm\) 0.27 \(\mathrm{\SIUnitSymbolMicro g}\)/g) followed by the brown _A. bisporus_ (0.55 \(\pm\) 0.06 \(\mathrm{\SIUnitSymbolMicro g}\)/g). On the contrary, very small quantities of ferulic acid were found in all the tested species. T-cinnamic acid was detected in all the tested samples, which corresponds to previous findings by [PERSON] et al. [31]. Substantial amounts of this compound were found in _P. nameko_ (2.64 \(\pm\) 0.06 \(\mathrm{\SIUnitSymbolMicro g}\)/g) as well as in _P. eryngii_ (1.15 \(\pm\) 0.61 \(\mathrm{\SIUnitSymbolMicro g}\)/g). In terms of 4-hydroxybenzaldehyde, its content ranged from 0.98 \(\pm\) 0.04 \(\mathrm{\SIUnitSymbolMicro g}\)/g (_P. nameko_) to 0.29 \(\pm\) 0.02 \(\mathrm{\SIUnitSymbolMicro g}\)/g (_L. edodes_). These results differ from previous findings in that many of the acids observed here have not been detected in the fruiting bodies of species such as _A. bisporus_, _L. edodes_, _P. ostreatus_, _P. eryngii_[32]. This discrepancy could be attributed to the less sensitive methods of detection (a photodiode array detector). In general, taking into consideration the total amounts of all the analyzed phenolic acids, the whole fruiting bodies could be ranked as follows: _P. nameko > P. eryngii > P. ostreatus > L. edodes > A. bisporus_ (brown) > _A. bisporus_ (white). The contents of phenolic acids depended on the part of the fruiting body. In general, the caps contained more phenolic acids compared to the stems regardless of the species; however, some exceptions are listed below. In the case of _A. bisporus_ (white), the stems contained slightly higher amounts of syringic acid, significantly higher content of 4-hydroxybenzaldehyde, and comparable amounts of ferulic and t-cinnamic acid. With regard to the brown _A. bisporus_, the stems were slightly richer in syringe acid and significantly richer in 4-hydroxybenzaldehyde. The stems of _L. edodes_ contained almost three times more syringic acid and similar amounts of t-cinnamic acid compared to the caps. In the case of _P. nameko_, only 4-hydroxybenzaldehyde content was substantially higher in the stems. And finally, in the stems of _P. ostreatus_, caffeic and syringe acids were present in higher amounts, whereas in _P. eryngii_ only syringic acid was richer. [PERSON] et al. [11] analyzed the fruiting bodies of two wild-growing species (_Amanita rubescens_, _Suillus granularatus_) and determined the p-hydroxybenzoic acid levels in different parts of each mushroom. Similar to the present findings, its content accumulated mostly in the caps. The amounts of phenolic acids, when calculated per gram of extract, were substantially higher compared the values per gram of fruiting body. This finding is consistent with that of [PERSON] and [PERSON] [33], who reported approximately three times higher contents of phenolic acids in _P. ostreatus extracts_ compared to fruiting bodies. The total sum of phenolic acids in the stems ranged from 3.97 \(\mathrm{\SIUnitSymbolMicro g}\)/g (the white _A. bisporus_) to 14.03 \(\mathrm{\SIUnitSymbolMicro g}\)/g (_L. edodes_), whereas in the caps it ranged from 4.9 \(\mathrm{\SIUnitSymbolMicro g}\)/g (the white _A. bisporus_) to 50.26 \(\mathrm{\SIUnitSymbolMicro g}\)/g (_P. nameko_). Figure 3: LC–MS chromatogram of _P.