Variation in the Main Health-Promoting Compounds and Antioxidant Capacity of Three Leafy Vegetables in Southwest China.

Malabar spinach (Basella alba), amaranth (Amaranthus tricolor), and sweet potato (Ipomoea batatas) are leafy vegetables found in Southwest China. The variation of chlorophyll, carotenoids, ascorbic acid, total flavonoids, phenolic compounds, and antioxidant capacity was studied in the leaves and stems of the three vegetables. The content of main health-promoting compounds and the antioxidant capacity in the leaves were higher than that in the stems, indicating that the leaves of the three vegetables possess greater nutritional value. The trend of total flavonoids in all three vegetables was similar to the trend of antioxidant capacity, suggesting that the total flavonoids may be the major antioxidants wihin these vegetables. Eight individual phenolic compounds were detected in three different vegetables. The most abundant levels of individual phenolic compounds in the leaves and stems of malabar spinach, amaranth, and sweet potato were 6'-O-feruloyl-d-sucrose (9.04 and 2.03 mg g-1 DW), hydroxyferulic acid (10.14 and 0.73 mg g-1 DW), and isorhamnetin-7-O-glucoside (34.93 and 6.76 mg g-1 DW), respectively. Sweet potato exhibited a higher total and individual phenolic compound content compared to malabar spinach and amaranth. Overall, the results demonstrate that the three leafy vegetables possess high nutritional value, and could be used not only for consumption but also in various other fields, including medicine and chemistry.

Grafting promoted antioxidant capacity and carbon and nitrogen metabolism of bitter gourd seedlings under heat stress.

Introduction: Heat stress can limit vegetable growth, and this can lead to constraints on agricultural production. Grafting technologies, however, can be used to alleviate various plant stresses. Methods: In this study, the differences in the heat stress impacts and recovery abilities of pumpkin and luffa rootstocks for bitter gourd were analyzed in terms of their antioxidant activity and carbon and nitrogen metabolism. Results: Compared with the un-grafted and self-grafted bitter gourd, which suffered from heat stress at 40°C for 24 h, heterologously grafted bitter gourd showed higher heat stability of the cell membrane (relative conductivity and malondialdehyde content were reduced), reduced oxidative stress (antioxidant enzyme activity was increased and the reactive oxygen species content reduced), and increased enzyme activity (sucrose phosphate synthase, sucrose synthase, neutral invertase, and acid invertase) and sugar content (soluble sugar, sucrose, fructose, and glucose) in carbon metabolism. The enzyme activity (nitrate reductase, nitrite reductase, and glutamine synthetase) and product content (nitrate and nitrite) of nitrogen metabolism were also found to be increased, and this inhibited the accumulation of ammonium ions. After the seedlings were placed at 25°C for 24 h, the heterogeneous rootstocks could rapidly restore the growth of the bitter gourd seedlings by promoting the antioxidant and carbon and nitrogen metabolism systems. When luffa was used as rootstock, its performance on the indexes was better than that of pumpkin. The correlation between the various indicators was demonstrated using a principal component and correlation analysis. Discussion: The luffa rootstock was found to be more conducive to reducing cell damage and energy loss in bitter gourd seedlings caused by heat induction through the maintenance of intracellular redox homeostasis and the promotion of carbon and nitrogen metabolism.

Variation in the Main Health-Promoting Compounds and Antioxidant Activity of Different Edible Parts of Purple Flowering Stalks (Brassica campestris var. purpuraria) and Green Flowering Stalks (Brassica campestris var. campestris).

Purple flowering stalks and green flowering stalks of Brassica campestris are widely cultivated in the middle and upper reaches of the Yangtze River. Here, concentrations of the main health-promoting compounds and antioxidant capacity levels were characterized in different parts (leaves, peel, flesh, and inflorescences) of purple and green flowering stalks. There were significant differences in the concentrations of health-promoting compounds between the two variants; the concentrations of pigments, especially anthocyanidins, and gluconapin, were significantly higher in purple flowering stalks than in green flowering stalks, and the progoitrin content was significantly higher in green flowering stalks than in purple flowering stalks. The leaves were judged to be the most nutritional edible part because they had the highest concentrations of pigments, ascorbic acid, proanthocyanidins, flavonoids, and total phenolics. Antioxidant capacity was also highest in the leaves, and it was positively correlated with the concentration of health-promoting compounds. Purple flowering stalks and green flowering stalks were found to be rich in health-promoting compounds, especially glucosinolates. Overall, our findings indicate that consumption of the leaves and peel would provide the most health benefits. Some suggestions are provided regarding the processing and utilization of these edible components.

Effect of the Number of Dark Days and Planting Density on the Health-Promoting Phytochemicals and Antioxidant Capacity of Mustard (Brassica juncea) Sprouts.

Mustard is an edible vegetable in the genus Brassica with tender and clean sprouts and short growth cycles that has become a rich source of nutrients required by humans. Here, the effects of dark exposure duration and planting density on the health-promoting phytochemicals and the antioxidant capacity of mustard sprouts were evaluated. The content of soluble sugar, soluble protein, chlorophyll, and carotenoids and the antioxidant capacity of mustard were higher in the two-day dark treatment; the content of indolic glucosinolates was also more affected in the dark day experiment than in the planting density experiment. The soluble sugar, soluble protein, and aliphatic and total glucosinolate levels were higher when sprouts were grown at high densities (6-7 g per tray); however, no significant variation was observed in the content of chlorophyll and carotenoids and the antioxidant capacity. The results of this study show that the optimum cultivation regime for maximizing the concentrations of nutrients of mustard plants is a planting density of 6 g of seeds per tray and a two-day dark treatment.

Physiological and Comparative Transcriptome Analysis Reveals the Mechanism by Which Exogenous 24-Epibrassinolide Application Enhances Drought Resistance in Potato (Solanum tuberosum L.).

Drought stress is a key factor limiting the growth and tuber yield of potatoes (Solanum tuberosum L.). Brassinosteroids (BRs) have been shown to alleviate drought stress in several plant species; however, little is known about the physiological and molecular mechanisms by which BRs enhance drought resistance in potatoes. Here, we characterized changes in the physiology and transcriptome of the tetraploid potato variety 'Xuanshu-2' in response to drought stress after 24-epibrassinolide (EBR) pretreatment. The abscisic acid (ABA) content, photosynthetic capacity, and the activities of antioxidant enzymes were increased; the intercellular CO2 concentration, relative conductivity, reactive oxygen species, malondialdehyde, proline, and soluble sugar content were decreased after EBR pretreatment compared with plants under drought stress. Transcriptome analysis revealed 1330 differently expressed genes (DEGs) involved in the response to drought stress after EBR pretreatment. DEGs were enriched in plant hormone signal transduction, starch and sucrose metabolism, circadian rhythm, flavonoid biosynthesis, and carotenoid biosynthesis. DEGs associated with the BR signaling and biosynthesis pathways, as well as ABA metabolic pathways were identified. Our findings provide new insights into the mechanisms by which BRs enhance the drought resistance of potatoes.