## 3 Results and Discussion
Pityochemicals in plants (GSLs, vitamin C, phenols, etc.) have antioxidant properties as important food quality features. Results revealed significant variability among phytochemicals in plant species and among plants grown under different animal manures. Ascorbic acid (vitamin C) and phenols concentrations in arugula were superior in plants grown in SS, CM, and HM amended soils in comparison to plants grown in no-manure (NM) control soil. The concentration of soluble sugars in arugula shoots (greens) revealed no significant differences among all the three animal manures tested, but greater than plants grown in NM control soil. Whereas SS and CM-amended soil increased total phenols in arugula compared to HM-amended soil (Figure 7A). Mustard grown in SS-, CM-, and HM-mixed soil contained the uppermost concentrations of ascorbic acid, total phenols, and soluble sugars (Figure 7B) compared to the NM control treatment. GSLs concentrations in mustard shoots were larger (1424 ug g\({}^{-1}\) fresh shoot) compared to arugula shoots (1250 ug g\({}^{-1}\) fresh shoot). This might be due to the greater proportion of the above-ground biomass of mustard related to arugula biomass. SS mixed with native soil elevated the concentration of GSLs in arugula and mustard shoots from 1006 and 927 ug\({}^{-1}\) fresh tissue in NM native soil to 1250 and 1424 ug\({}^{-1}\) fresh tissue, respectively (Figure 8), whereas GSLs in arugula and mustard shoots of plants grown in CM or HM amended soils were significantly lower compared to SS amended soil. [PERSON] and [PERSON] [60] described a remarkable activity of the enzyme myrosinase (glucosidase) by ascorbic acid and in some situations, myrosinase is entirely inactive in the absence of ascorbic acid. Figure 7: Concentrations of soluble sugars, ascorbic acid (AA), total phenols \(\pm\) std. error in arugula (**A**) and mustard (**B**) grown under different soil management practices. Statistical analysis comparisons were carried out among four soil treatments of each parameter. Statistical analyses were done via [PERSON]’s multiple range test in SAS [26]. Values with the same letter are not significantly different (\(p\geq 0.05\)). The greater content of ascorbic acid (vitamin C), phenols, and soluble sugars in arguula and mustard plants grown in animal manure-amended soil could be due to the higher synthesis of these water-soluble phytochemicals by Brassica leaves. It might also be due to improved absorption from the soil rhizosphere by the plant roots. This increase might also be due to increased soil organic matter and microbial activity after the addition of animal manures. SS, CM, and HM contain several enzyme substrates that activate either urease, invertase, and phosphatase, respectively, and other hydrolyzing enzymes. Regardless of crop type, Figure 9 also revealed a significant increase in ascorbic acid (vitamin c), total phenols, and sugars in plants grown in SS, CM, and HM compared to NM control soil. Accordingly, the pronounced increase in these three phytochemicals could be due to increased microbial activity and their enzyme excretions after mixing native soil with animal manure. Many reasons were reported in the literature review for this increase, but none were extensively investigated. Studies carried out by [PERSON] et al. [61] revealed that animal manure increased soil enzyme activity. Soil enzymes secreted by soil microorganisms also promote many soil processes such as the synthesis of humus substances and the breakdown of organic matter in soil and the release of nutrients to growing plants. Among the phytochemicals that provide health benefits in human nutrition are polyphenols, flavonoids, isoflav, anthocyan, phytoestrogens, terpenoids, carotenoids, vitamin C, limonoids, phytosteros, glucosinolates, isothi cyanates (ITCs), and fibers.