## 3 Results and Discussions
### Evaluation of Cytotoxicityicity and Protective Effect in Fibroblast Cell Line HS-68  
HS68 cell line was used as in vitro model to investigate the cytotoxic and protective effect of _M. nodiforum_ SFE extract. The effects of the treatments on the cells were preliminarily evaluated on a wide range of concentrations (5-50 ug/mL), through dose-dependent assays, to check the possible toxicity of the compounds. The treatment for 48 h did not induce any mortality for toxicity compared to control (data not shown).  
Similar results have been obtained from [PERSON] et al. [51] in a keratinocyte cell line (HaCaTs) treated with different doses of ice plant extract.  
The protective effect of our _M. nodiforum_ SFE extract, against oxidative stress, was tested at two concentrations, 5 and 10 ug/mL. For the induction of oxidative stress, a standardized protocol, that uses 10 uM hydrogen peroxide (HP), to induce toxicity in this cell line [26; 38; 39], was used. A comparison also with the synthetic antioxidant N-acetyl cysteine (NAC) (Merck KGaA, Darmstadt, Germany) was done.  
The cell vitality, determined by the MTT test, showed, as expected, a significant vitality reduction (\(p<0.05\)) in cells exposed to the HP, compared to the control (Figure 4). On the contrary, cells pretreated with the synthetic antioxidant NAC and then exposed to HP, resulted protected against mortality, respect to the treatment with HP alone, reporting only 10% and 25% of the vitality reduction at 24 and 48 h (Figure 4). Similarly, pre-treating cells with _M. nodiforum_ SFE extract, before the exposure to HP, determined a significant protection against mortality, maintaining the vitality of cells compared to the control, also after exposure to the HP. These results indicate that the natural antioxidant is able to protect cells from oxidative stress, as the synthetic antioxidant.  
The increased vitality of cells treated with _M. nodiforum_ SFE extract and subsequently subjected to stressors, can be related to the antioxidant power of the plant, attested by the DPPH radical scavenging activities [10] and reducing power. Similar results were obtained by [PERSON] et al. [52], who demonstrated that the treatment of human dermal fibroblasts, with ice plant callus extract, before UV exposure, positively affected the antioxidant activity.  
Our data suggest that _M. nodiforum_ SFE extract given its significant antioxidant capacities protecting cells against oxidative stress-induced mortality.  
Figure 4: Effect of _M. nodiforum_ supercritical fluid extract (SFE) on the vitality of fibroblast cells exposed to oxidative stress, induced by hydrogen peroxide (HP). Control: cells maintained in standard culture conditions; HP: cells exposed to hydrogen peroxide (10 uM); NAC: cells treated with N-acetyl cystein (5 mM) and subsequently exposed to HP (10 uM); 5 and 10 ug/mL: cells treated with 5 and 10 ug/mL of _M. nodiforum_ SFE and then exposed to HP (10 uM). Lowercase letters (a–b) indicate superscript letters indicate a significant difference compared to the control at 24 h. Capital letters (A–C) indicate significant differences compared to the control at 48 h (\(p<0.05\)).