## 3 Results and Discussion
### Bioactive Compounds
Therefore, the greater accumulation of vitamin C will provide a plant with better characteristics and better fruit quality. The fruit lycopene content increased significantly with the application of Cu NPs (Table 3). The application of 50 mg L\({}^{-1}\) of Cu NPs increased it by 105.26%, 250 mg L\({}^{-1}\) of Cu NPs increased it by 61.24%, 500 mg L\({}^{-1}\) of Cu NPs increased it by 65.1%, and 125 mg L\({}^{-1}\) of Cu NPs increased it by 56.77% compared to the Control. Similar results were obtained in tomato fruits when applying Cu NPs + chitosan, where an increase of 12% was reported compared to the Control [16]. Likewise, the foliar application of NPs of TiO\({}_{2}\) and ZnO (0-1000 mg kg\({}^{-1}\)) increased the lycopene content (80-113%) in tomato fruits [49]. As in the case of vitamin C, the increase in lycopene is directly related to the induction of antioxidant compounds by the application of Cu NPs [17]. In plants, lycopene synthesis is usually derived from the mevalonic acid (MVA) and methylerythntol phosphate (MEP) pathways. These pathways synthesize isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP), which function as precursors to the synthesis of carotenoids [50]. Lycopene is one of the main carotenoids in tomato fruits, and it is also one of the main antioxidants [3; 41]. Moreover, the antioxidant actions of carotenoids are based on their ability to quench singlet oxygen and to trap \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Treatment** & **T Prof** & **Vit C** & **Iyc** & **GSH** & **T Phen** & **Flav** & **ABTS (0)** & **ABTS (aa)** \\ \hline
500 mg L\({}^{-1}\) Cu NPs & 8.66 c & 6.34 c & 3.17 a & 2.68 a & 306.24 ab & 64.08 e & 7.44 ab & 1.46 ab \\
250 mg L\({}^{-1}\) Cu NPs & 13.88 b & 10.41 a & 3.51 a & 1.55 b & 326.19 a & 84.71 b & 7.17 bc & 1.41 bc \\
125 mg L\({}^{-1}\) Cu NPs & 13.65 b & 8.80 b & 3.01 a & 1.91 b & 264.68 c & 80.77 c & 7.55 a & 1.48 a \\
50 mg L\({}^{-1}\) Cu NPs & 15.34 a & 6.45 c & 3.96 a & 1.87 b & 276.41 bc & 99.67 a & 7.67 a & 1.50 a \\ Control & 7.68 c & 4.69 d & 1.92 b & 1.97 b & 309.37 b & 73.21 d & 7.09 c & 1.40 c \\ CV (\%) & 9.17 & 12.49 & 25.30 & 22.15 & 9.03 & 3.70 & 3.37 & 3.07 \\ \hline \hline \end{tabular} Each unit of data is the average of six replicates. CV: coefficient of variation. Different letters per column indicate significant differences between treatments according to the LSD Fisher test (\(p\leq 0.05\)). T Prot: total proteins, expressed as mg g\({}^{-1}\) of dry weight. Vit C: vitamin C as mg 100 g\({}^{-1}\) Fresh Weight (FW). Lyc: lycopene as g\({}^{-1}\) FW. GSH: glutathione as mM equivalent of GSH mL\({}^{-1}\) min\({}^{-1}\) total protein\({}^{-1}\). T Phen: total phenols as the mg equivalent of gallic acid 100 g\({}^{-1}\) of dry weight. Flav: flavonoids as mg equivalent quercetin 100 g\({}^{-1}\) of dry weight. ABTS: 2,2/azinobis(3-ethylmethaniazol-6-sulfonic acid). t. mg equivalent Trolox 100 g\({}^{-1}\) dry weight. aa: mM equivalent ascorbic acid 100 g\({}^{-1}\) dry weight.  
\end{table} 
Table 3: The non-enzymatic antioxidant compounds in tomato fruits with the application of Cu NPs. peroxyl radicals [51; 52; 53]. Specifically, lycopene is one of the most efficient singlet oxygen neutralizers among the natural carotenoids [52]. The results indicate that the overproduction of these carotenoids is a response to oxidative stress caused by Cu NPs [54]. One of the functions of lycopene in plants is related to photo- and chemo-protection. As an antioxidant, lycopene counteracts the ROS [51]. The production of foods rich in lycopene is of utmost importance; therefore, the application of Cu NPs represents a viable option. The GSH increased by 36.04% with the application of 500 mg L\({}^{-1}\), while the rest of the treatments equaled the Control (Table 3). This response can be derived from the stress caused by the applied nanoparticles [43; 44]. This indicates that the highest dose of Cu NPs generated a certain degree of toxicity in tomato plants.