## 3 Results and Discussion
### Minerals, Primary and Secondary Metabolites of Red Topepo Fruits

Table 1: Ion content (mg g\({}^{-1}\) dw) in red _Topepo_ fruits grown in unfertilized soil (control, CTR) and soils fertilized with compost from olive wastes (CO), compost from vegetable wastes (CV), and horse dune (HD). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**ID** & **CTR** & **CO** & **CV** & **HD** \\ \hline Carbohydrate & 0.64 \({}^{\text{c}}\)\(\pm\) 0.11 & 1.20 \({}^{\text{b}}\)\(\pm\) 0.03 & 1.61 \({}^{\text{a}}\)\(\pm\) 0.11 & 1.18 \({}^{\text{b}}\)\(\pm\) 0.21 \\ Soluble protein & 631.29 \({}^{\text{c}}\)\(\pm\) 10.88 & 644.22 \({}^{\text{b}}\)\(\pm\) 30.11 & 707.48 \({}^{\text{b}}\)\(\pm\) 44.42 & 1028.06 \({}^{\text{a}}\)\(\pm\) 30.08 \\ Total phenols & 451.26 \({}^{\text{b}}\)\(\pm\) 53.51 & 405.57 \({}^{\text{c}}\)\(\pm\) 15.51 & 643.22 \({}^{\text{a}}\)\(\pm\) 58.05 & 519.46 \({}^{\text{b}}\)\(\pm\) 16.27 \\ Ascorbic acid & 93.18 \({}^{\text{b}}\)\(\pm\) 8.99 & 94.90 \({}^{\text{b}}\)\(\pm\) 15.13 & 159.11 \({}^{\text{a}}\)\(\pm\) 9.50 & 97.19 \({}^{\text{b}}\)\(\pm\) 5.73 \\ Carotenoids & 614.67 \({}^{\text{c}}\)\(\pm\) 13.32 & 637.97 \({}^{\text{c}}\)\(\pm\) 10.03 & 1582.05 \({}^{\text{a}}\)\(\pm\) 52.05 & 686.08 \({}^{\text{b}}\)\(\pm\) 12.01 \\ Vitamin E & 0.63 \({}^{\text{b}}\)\(\pm\) 0.01 & 0.69 \({}^{\text{b}}\)\(\pm\) 0.01 & 1.05 \({}^{\text{a}}\)\(\pm\) 0.18 & 0.90 \({}^{\text{a}}\)\(\pm\) 0.01 \\ Flavonoids & 2.53 \({}^{\text{d}}\)\(\pm\) 0.06 & 4.31 \({}^{\text{c}}\)\(\pm\) 0.14 & 5.21 \({}^{\text{a}}\)\(\pm\) 0.12 & 4.72 \({}^{\text{b}}\)\(\pm\) 0.07 \\ \hline \hline \end{tabular} a, b, c, d Letters show significant differences among the treatments (Tukey’s test. \(p\)-level \(\leq\) 0. 05).  
\end{table} 
Table 2: Primary and secondary metabolites in red _Topepo_ fruits grown in unfertilized soil (control, CTR) and soils fertilized with compost from olive wastes (CO), compost from vegetable wastes (CV), and horse dune (HD). Carbohydrate, soluble protein, ascorbic acid, carotenoids, and vitamin E were expressed as mg/100 g FW. Total phenols were expressed as mg gallic acid/100 g FW and flavonoids as rutin (R) E/g FW. and in particular their concomitant presence in fertilizers, have a significant effect on the accumulation of phenols and antioxidants [44]. As demonstrated by [PERSON] et al. [45] in _Labisia punila Benth var. alata_, the potassium fertilization levels increased not only the production of soluble proteins but also the carbohydrate content that simultaneously increased the synthesis of secondary metabolites in _L. punila_, increasing the health promoting effects of this plant. Additionally, [PERSON] et al. [46] evidenced in _Salvia officinalis_ L., an increase in secondary metabolites in the presence of a high percentage of phosphorous. [PERSON] et al. [47] showed in cereal species, that increasing S fertilization enhanced the N and C uptake efficiency and use as well as the synthesis of plant bioactive compound because S is an essential constituent of key enzymes involved in the secondary metabolite synthesis [48]. Our results confirmed these findings and are in agreement with data of [PERSON] [49] and [PERSON] et al. [50], providing evidence that the chemical composition of organic fertilizers modulates the synthesis of secondary metabolites in plants. CV richer in macronutrients than the other fertilizers stimulated plant metabolism and antioxidant compound synthesis more than the other two organic fertilizers. CV enhanced also significantly the amounts of ascorbic acid, vitamin E, doubling in particular the amount of carotenoids in respect to the other treatments and CTR. Total water soluble phenols, ascorbic acid, flavonoids, vitamin E, and carotenoids are well known powerful antioxidants with a key role in the prevention of various chronic metabolic disorder including cancers and cardiovascular diseases, thus their observed increase, modulated by the use of organic fertilizers and particularly by CV, can be a way for increasing sustainably the economic and nutraceutical values of red _Topepo_.