## 4 Discussion
The peaks observed at 1633 and 1700 cm\({}^{-1}\) can be assigned to the C=O, C-N, and/or C-O-NH- vibrations which may be due to proteins [67]. The aromatic and N-H bending vibrations found at 1511, 1541, 1560, and 1576 cm\({}^{-1}\) can depict the presence of amino acids [67]. The bands at 1511 and 1576 cm\({}^{-1}\) were observed only for _cc_UB and _d_UB, indicating the differences in amino acids and proteins compared to the _mc_UB sample; this hypothesis is supported by the appearance of the peak at 1440 cm\({}^{-1}\). The peaks in the regions 1377-1460 cm\({}^{-1}\) can also be assigned to the CH\({}_{3}\) lipids/proteins and COO- of amino acids, while the vibrations of N-H and C-N had peaks at 1460-1576 cm\({}^{-1}\)[64] and \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Legislative** & **WHO/EU** & **WHO** & **Eu.Ph.** & **Ch.Ph.** & **Heavy Metals Content** \\
**Authority** & [60;61] & [62] & [63] & [59] & **in** _U. barbata_ (\#g/g) \\ \hline \multirow{2}{*}{**Heavy Metal**} & \multicolumn{4}{c}{**Permissible Limits (\(\mu\)g/g)**} \\  & **Edible Plants** & \multicolumn{4}{c}{**Medicinal Plants**} \\ \hline As & 0.5 & 10 & & 2 & ND & 0.219 & ND \\ Cd & 0.02 & 0.2 & 1 & 0.3 & ND & 0.164 & ND \\ Cr & 1.3 & & 2 & & ND & 0.225 & ND \\ Co & 0.01 & & & & 1.002 & 2.494 & 0.864 \\ Cu & 10 & 20 & & 20 & 1.523 & 2.246 & 1.286 \\ Hg & 0.03 & 1 & 0.1 & 0.2 & 0.671 & 0.708 & 0.539 \\ Ni & 0.1 & & & & 0.449 & 1.033 & 0.355 \\ Pb & 2 & 10 & 5 & & 1.296 & 2.177 & 0.584 \\ V & 0.03 & & & 0.241 & 1.237 & ND \\ Zn & 50 & 50 & & & 20.536 & 33.223 & 13.588 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Permissible limits for heavy metals in edible and medicinal plants and their content in _U. barbata_ whole lichen (_d_UB) and fractions (_mc_UB and _cc_UB). reveal the presence of proteins in _U. barbata_ fractions. The bands observed in the region 1323-1440 cm\({}^{-1}\) could be attributed to the primary or secondary O-H bending (in-plane) and phenol or tertiary alcohol (O-H bend) [67]; the peak at 1440 cm\({}^{-1}\) was observed only in _cc_UB and _d_UB samples. The secondary aromatic amine and CN stretching vibration could be responsible for the peaks obtained at 1293 and 1323 cm\({}^{-1}\), while the band observed at 1253 cm\({}^{-1}\), attributed to the C-O stretching vibrations, could be due to acids or esters [67]. The specific bands at 1293 and 1323 cm\({}^{-1}\) could be associated with username A, a detected compound in _U. barbata_ lichen [70]. The peaks obtained at 1042 and 1073 cm\({}^{-1}\) can be due to the C-O stretching vibrations of carbohydrates and glycoproteins. The most important phenolic secondary metabolites (usnic acid, for _Usnea_ sp.) synthesized by mycobionts are deposited on the hyphae surface in the cortex and medulla [37; 71]. Therefore, the highest TPC values in _mc_UB in both solvents, followed by _d_UB and _cc_UB, could be justified. Usnic acid and other specific secondary metabolites have a higher solubility in acetone than ethanol; this property can explain that _mc_UB has a higher TPC value in acetone extract than ethanol extract [32]. The free radical scavenging activity [72] was evaluated, and, in both extracts, dUB recorded the most significant antiradical potential [73], followed by _mc_UB and _cc_UB. However, due to the various free radical scavenging ability of phenolic metabolites found in each lichen extract (ethanol and acetone), AA values considerably differed. Consequently, the correlation between antiradical activity and TPC recorded significant variations. The highest AA of _d_UB in both extracts could be induced by the synergic interaction between the primary metabolites with a non-phenolic structure, the secondary ones, and the metals found in the whole lichen.