3.4.3. Nonspecific Esterase Activity Assay

Cell suspension (1 × <sup>10</sup><sup>3</sup> cells/well) was incubated with different concentrations of the studied compounds during 24 h. A stock solution of the fluorescein diacetate (FDA) (Sigma-Aldrich, USA) in DMSO (1 mg/mL) was prepared. After incubation of the cells with compounds, FDA solution (50 μg/mL) was added to each well and the plate was incubated at 37 ◦C for 15 min. Cells were washed with phosphate buffer saline and fluorescence was measured with a Fluoroskan Ascent plate reader (ThermoLabsystems, Finland) at λex = 485 nm and λem = 518 nm. Cell viability was expressed as the percent of control.

#### 3.4.4. 6-OHDA-Induced In Vitro Model of Parkinson's Disease

The neuroprotective activity of the studied compounds in 6-hydroxydopamine-induced cell model of Parkinson's disease was investigated as described previously [37]. Neuroblastoma Neuro2a line cells (1 × <sup>10</sup><sup>3</sup> cells/well) were treated with compounds at concentrations of 1 and 10 <sup>μ</sup>M during 1 h, after that 6-OHDA (Sigma-Aldrich, USA) at concentration of 50 μM was added in each well and neuroblastoma cells were cultivated during 24 h. After that, viability of cells was measured by MTT assay. The results were presented as percent of control data.
