Tomatoes are rich in secondary metabolites such as lycopene, β-carotene, phenolics, flavonoids, and vitamin C, which are responsible for their antioxidant activates. A high level of γ-Aminobutyric acid (GABA), a health-promoting functional compound, was also found to accumulate in tomato fruit. In addition to the internal quality attributes, the acceptance of the tomato fruit by consumers is highly dependent on appearance and taste. Hence, we conducted this study to evaluate ‘Tori’, ‘TY VIP’, ‘Mamirio’, and ‘Arya’ tomato cultivars based on their physicochemical characteristics, contents of secondary metabolites, and GABA content. The results have revealed that the tested cultivars were very firm, which renders them the best choice for postharvest distribution of fresh market tomatoes as they resist impacts during harvesting and postharvest operations. Based on total soluble solids (TSS), titratable acidity (TA), and Brix acid ratio (BAR) the choice of cultivar could be ‘Mamirio’ > ’Tori’ > ‘TY VIP’ > ‘Arya’. Apart from flavor intensity, ‘Mamirio’ and ’Tori’ also revealed the highest content of ascorbic acid while ‘Mamirio’ and ‘Arya’ had the highest carotenoids (lycopene and β-carotene) accumulation. On the other hand, the highest total phenolics content was recorded from ‘TY VIP’ and ‘Arya’. Moreover, the highest total flavonoids and GABA contents were recorded from ‘TY VIP’. Nevertheless, the antioxidant activity of ‘TY VIP’ was the lowest of all tested cultivars while the highest was recorded from ‘Mamirio’. Taken together, the findings of the present study could suggest that the consumers’ requirements could be better fulfilled by choosing cultivars for the specific target functional compounds. From the tested cultivars, if the target is ascorbic acid, carotenoids, and antioxidant activity then ‘Mamirio’ is the best choice. On the other hand, if the target is total phenolics, flavonoids, and GABA then ‘TY VIP’ is the best choice. One could also label ‘Mamirio’ as an ‘antioxidant tomato’ and ‘TY VIP’ as the ‘GABA tomato’.

Vertical hydroponics farming has emerged as an alternative solution to feed the continuously growing world population. Additionally, recent studies reported that the exogenous treatments of jasmonic acid influence the phytochemical composition of Brassicaceae. We conducted this study to determine the effect of preharvest methyl jasmonate (MeJA) treatment on the phytochemical composition and antioxidant activities of soil- and hydroponically grown pak choi. An aqueous solution of 0.5-mM MeJA was sprayed to saturation on the aerial plant part three days before harvest. The harvested pak choi was freeze-dried and then powdered to measure the antioxidant activity and the contents of chlorophylls (Chls), total phenolics and flavonoids, and glucosinolates (GSLs). The overall results revealed that pak choi grown in vertical hydroponics had higher total Chls and total phenolics than those grown in soil in the greenhouse, regardless of MeJA treatment. Nevertheless, the GSLs content and total flavonoids increased significantly due to MeJA treatment in both growing systems, and the highest values were recorded in hydroponically grown MeJA-treated pak choi. Similarly, the 2, 2-di-phenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, Trolox-equivalent antioxidant capacity (ABTS), oxygen radical absorbance capacity (ORAC), and ferric-reducing antioxidant power (FRAP) were highest in hydroponically grown MeJA-treated pak choi. Taken together, the preharvest foliar treatment of MeJA can be used to improve the phytochemical composition of pak choi grown in both growing systems. Interestingly, the results strongly support the use of MeJA treatment in the vertical hydroponics growing system compared to the conventional growing system in the soil. This indicates that supplementing the vertical hydroponic growing system with preharvest MeJA treatment could be the best option to improve both the yield per square meter and the quality of pak choi. Besides, MeJA-treated pak choi could be used as a value-added horticultural commodity, as its antioxidant activity increased after treatment. Moreover, after further studies, MeJA could also be applied to other Brassica vegetables to improve their GSL contents and antioxidant properties.

Glycoalkaloids (GAs) are toxic to humans at higher concentrations. However, studies also suggest the health benefits of GAs depending on the dose and conditions of use. Methods that have been used to determine GA content in potato tubers are destructive and time-consuming and require skilled personnel and high-performance laboratory equipment. We conducted this study to develop indices for the prediction of the level of total GAs in potato tubers at different greening stages based on surface color readings and chlorophyll (Chl) development. Color values (Hunter L*, a*, b*, a*/b*), Chls (Chl a, Chl b, and total Chls) and GA (α-solanine, α-chaconine, and total GAs) content were measured from tubers of ‘Atlantic’ and ‘Trent’ potato cultivars at three-week intervals in up to six greening stages during the storage at room conditions (22 °C, 12-h shift of light-dark cycles). The results have revealed that greening, Chls, and GA content significantly increased for the two cultivars as the stage proceeded. The toxic level of GAs (>200 mg kg⁻¹ FW) was accumulated at the late greening stages, accompanied by the highest Chl content. Finally, indices were developed based on surface color and Chl content for estimation of the safe GA levels for the consumption of the two commercially and commonly used potato cultivars. Moreover, the developed indices could be used as basic information to adapt to other potato cultivars.