# Cytoprotective-Antioxidant Effect of _Brunfelsia grandiflora_ Extract on Neuron-like Cells
## 4 Discussion
In fact, we have recently reported a similar outcome for another South American medicinal fabaceae, _Desmodium tortuosum_, in identical cell model conditions [6], suggesting that the constant presence of the potent prooxidant in the cotreatment condition seems more severe for the cell culture, reducing the efficiency of the extract compounds in rescuing the depleted GSH to suitable levels in the cells. Nevertheless, the positive recovery of GSH in stressed neuron-like cells treated with _B. grandiflora_ extracts agrees with previous studies of other phenolic antioxidant-rich extracts in neuron-like cells [5; 6]. This recovery of GSH concentration above a suitable threshold while fighting a stressful insult is critical for cell survival [35; 36]. As we have reported for an SH-SYSY cell culture, the addition of t-BOOH (co- and pretreatment) produced a substantial rise in GPx and GR activities in order to face the stress-induced overproduction of ROS [5; 6]. GPx, with the help of GSH, catalyzes the reduction of peroxide species and forms oxidized glutathione, whereas GR catalyzes oxidized glutathione to GSH to maintain the steady state of cellular reducing power [35; 36]. Thus, the stimulation of the antioxidant enzyme defenses observed after exposure to t-BOOH unequivocally shows an adequate response of the antioxidant defense system to an oxidative challenge [13; 14; 35]. The significant decrease in GPx and GR activities when stressed neuron-like cells were co- or pretreated with the _B. grandiflora_ extracts clearly indicates an efficient quenching of ROS, followed by a return to a basal condition that decreases cellular damage and prepares the cell to cope with impending oxidative insults. This enzymatic antioxidant response by antioxidant-rich phenolic extracts agrees with our previous data on the same neuron-like cell culture model [5; 6], as well as on other cell lines [13; 14]. Thus, the chemoprotective mechanism of exogenous antioxidants that modulates the antioxidant enzyme response to oxidative stress is an overall means of cellular protection. On the other hand, we also molecularly evaluated three biomarkers related to oxidative status (NF\(\kappa\)B, NRF2, and SOD). In the present study, we have shown that NF\(\kappa\)B, NRF2, and SOD return to control-like levels in SH-SYSY neuronal cells due to _B. grandiflora_ extract after their levels were altered by t-BOOH, both in cotreatment and pretreatment, as reported in other studies [6; 40; 41; 42]. The exacerbation of cellular oxidative stress is closely related to the activation of cell death biomarkers such as caspase-3/7 enzymes, the Bax/BNIP3/APAF1 regulator, and others [36]. In our study, we observed that oxidative stress increased due to the effect of the compound t-BOOH, and it is possible that this generated an increase in the activity of caspase-3/7 and apoptosis mediators (BAX, BNIP3, and APAF1) in SH-SYSY cells. This effect, in turn, was reversed in a dose-dependent manner by _B.grandiflora_ extract; this effect is closely related to the phenolic compound content of this plant [9]. Similar effects were reported in other studies, showing that plant extracts or plant-derived compounds have the potential to reduce apoptosis through the reduction of caspase-3/7 activity [6]. Perooxidation of polyunsaturatedated fatty acids generates MDA, which is used as an index of oxidative damage to lipids in biomedicine [25]. Since MDA has been reported to be elevated in diseases caused by oxidative stress, the remarkable decline in MDA in stressed neuron-like cells co- or pretreated with the _B. grandiflora_ extracts indicates a decrease in lipid peroxidation and cellular damage. This outcome also points to a potential therapeutic effect in the prevention of pathologies resulting from oxidative stress, such as neurodegenerative diseases. Again, a similar chemoprotective mechanism of lipid peroxidation has been previously reported in hepatic [13; 14], colonic [43], and endothelial cells [44], but interestingly, never in neuron-like SH-SY5Y cells.