*2.3. Lichen Extracts from Cetrarioid Clade Improved Oxidative Stress Markers and Antioxidant Enzyme Activity*

Exposure to hydrogen peroxide significantly increased thiobarbituric acid reactive substances (TBARS) levels (174%), impaired GSH content (51%) and reduced SOD (68%) and CAT activity (58.5%) in SH-SY5Y cells compared to control cells (100%) (Figure 4). However, pretreatments with methanol lichen extracts of cetrarioid clade exhibited noteworthy protection against hydrogen peroxide-induced oxidative injury by improving the antioxidant status. Hence, *D. arctica* and *V. pinastri* significantly reduced lipid peroxidation levels (109% and 122%, respectively), restored GSH content (93% and 83.5%, respectively) and increased SOD activity (96% and 87%, respectively). Moreover, *T. americana* also augmented SOD enzyme activity by 92%. All the extracts significantly increased CAT activity, reverting H2O2 effects. *D. arctica*, *V. pinastri* and *T. americana* showed the highest values (100.9%, 97% and 95%, respectively), followed by *N. stracheyi*, with moderate CAT activity (81.6%).

**Figure 4.** Lichen extracts from cetrarioid clade improved oxidative stress markers and antioxidant enzyme activity. SH-SY5Y cells were pretreated with *Dactylina arctica* (*D.a*), *Nephromopsis stracheyi* (*N.s*),

*Tuckermannopsis americana* (*T.a*) and *Vulpicida pinastri* (*V.p*) for 24 h before H2O2 (250 μM, 1 h). (**A**) Lipid peroxidation, (**B**) GSH levels and (**C**) SOD activity, (**D**) CAT activity. Results are expressed as mean ± SD (triplicate experiments). \* *p* < 0.05 versus control; # *p* < 0.05 versus H2O2.
