*2.9. Neuronal Cell Viability Assay*

The cytotoxicity assay was carried out on P19-derived neurons cultured in a 96-well plate. After 14 days of differentiation process, the α-MEM supplemented with 10% FBS, 10 μM Ara-C, and 1% antibiotics-antimycotic solution (P19SM) was removed, and DMSO solutions of the sample, diluted with the P19SM were added to give the concentrations of 10,000, 1000, 100, 10, and 1 ng/mL [20–24]. The 0.5% *v/v* DMSO in P19SM was used as control. The cells were incubated for 18 h at 37 ◦C. Then 150 μL of the medium was removed, and 50 μL of XTT solution (1 mg/mL XTT in 60 ◦C α-MEM + 25 μM PMS) was added. After incubation at 37 ◦C for 4 h, 100 μL of PBS (phosphate buffer saline solution) pH 7.4 was added. The OD value was determined on a microplate reader at 450 nm. The data were expressed as the average % cell viability ± SE (*n* = 3, each *n* was run in triplicate). The samples that enhanced survival of cultured neurons more than control (0.5% *v/v* DMSO in the medium) will be further investigated for their neuroprotective ability.

#### *2.10. Neuroprotective Assay*

The assays were carried out on P19-derived neurons cultured in a 96-well plate and performed for three independent experiments each experiment was run in triplicate [21–26].

#### 2.10.1. Serum Deprivation Method

The DMSO solution of the extracts diluted with the α-MEM supplemented with 1% antibiotics–antimycotic solution and 10 μM Ara-C without FBS were added to give the final concentration of the extract at concentration that enhanced survival of cultured neurons more than control. The 0.5% *v/v* DMSO in the completed medium (P19SM, α-MEM supplemented with 1% antibiotics–antimycotic solution and 10 μM Ara-C with 10% *v/v* FBS) was used as control. The 0.5% *v/v* DMSO in α-MEM supplemented with 10 μM Ara-C, and 1% antibiotics–antimycotic solution without FBS was used to make oxidative stress condition. The cells were incubated for 18 h at 37 ◦C. Cell viability was assayed by XTT reduction method. The data were expressed as the average % cell viability ± SE (*n* = 3) [10–14]. Quercetin at concentration of 1 nM was used as positive control [26].
