Fig. (5).

Mechanisms of action proposed for the EOs of Aloysia cytrodora and Salvia lavandulifolia on in vitro models for neurological disorders. Subtitle. Aloisia cytrodora presented important mechanisms of action in an in vitro model for Alzheimer's disease induced by H₂O₂ and β-amyloid. Its EO exhibited antioxidant and radical scavenging activities in additional to significant protective properties when compared to H₂O₂ and β-amyloid-induced neurotoxicity. It shows an iron chelation activity in vitro through hydroximation of Fe³⁺ to Fe²⁺, which is an important mechanism as the transition metal ions contribute to the oxidative damage involved in neurodegenerative disorders. Therefore, the chelation of transition metals avoids decomposition catalysis of H₂O₂ via the Fenton type reaction. Conversely, Salvia lavandulifolia presented protective mechanisms even after induction of H₂O₂ toxicity. Salvia lavandulifolia is able to activate the transcription factor Nrf2 (regulator of antioxidant genes) as the protein expression and the activity of CAT, HO-1, SOD and GPX are reduced, which correlates with the decrease in the levels of Nrf2. Thus, treatment with S. lavandulifolia regulated Nrf2 and concomitantly increased HO-1, which results in decreased ROS formation and increased cell viability when compared with the group exposed to H₂O₂ without S. lavandulifolia essential oil. In addition, it reduced the levels malondialdehyde (MDA) induced by H₂O₂ and avoided mitochondrial damage due to its inhibition effect over caspase 3 (effector of apoptosis). (A higher resolution/colour version of this figure is available in the electronic copy of the article).