*2.2. Lichen Extracts from Cetrarioid Clade Reduced ROS Production after H2O2-Induced Oxidative Stress*

Figure 3 revealed a significant increase in intracellular ROS production when SH-SY5Y cells were treated with hydrogen peroxide. 1 h treatment with H2O2 at 250 μM enhanced ROS generation by 155.5% compared to control cells (100%). On the other hand, 24 h pretreatments with methanol lichen extracts significantly reduced ROS production. In particular, the highest reduction was shown by *D. arctica* (42.4% of reduction compared to hydrogen peroxide treatment), followed by *T. americana* (41.1% of reduction versus H2O2), *N. stracheyi* (38.7% of reduction versus H2O2) and *V. pinastri* (35.3% of reduction versus H2O2).

**Figure 2.** *Cont*.

*N. stracheyi* (25 μg/mL) + H2O2

**Figure 2.** (**A**) Effect of methanol lichen extracts of cetrarioid clade on cytoprotection in stress oxidative models. SH-SY5Y cells were pretreated with non-cytotoxic concentrations of lichens for 24 h before H2O2 (250 μM, 1 h). Cell viability was determined using MTT assay. Results were expressed as mean ± SD (triplicate experiments). \* *p* < 0.01 versus control; # *p* < 0.01 versus H2O2. (**B**) SH-SY5Y cells morphology after treatments.

(**B**)

**Figure 3.** Effect of methanol lichen extracts of cetrarioid clade on intracellular ROS production. SH-SY5Y cells were pretreated with *D. arctica* (*D.a*), *N. stracheyi* (*N.s.*), *T. americana* (*T.a*) and *V. pinastri* (*V.p*) for 24 h before H2O2 (250 μM, 1 h). The levels of intracellular ROS production were measured using dichlorodihydrofluorescein diacetate (DCFH-DA) method. Results are expressed as mean ± SD (triplicate experiments). \* *p* < 0.01 versus control; # *p* < 0.01 versus H2O2.
