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Hydrogen peroxide (H2O2) is a reactive oxygen species (ROS) which participates in the signal transduction responses of plants toward biotic and abiotic stresses. Therefore, the objective of this study was to link the exposure of low doses of H2O2 to the improvement of the phytochemical composition of broccoli florets, in particular the content of glucosinolates (GLS), and hydroxy-cinnamates (HCA) without affecting the quality parameters of the vegetable. A dose of 1.25 mM H2O2 applied for 180 min was effective (hormetic) in maintaining the color of broccoli florets, which was also compared with a higher dose of 5.0 mM H2O2 applied for 180 min. The intensity of the treatments was related to respiration rate, which was monitored for 21 d at 4◦C along to weight loss. The initial respiration rate of florets exposed to both doses of H2O2 was significantly (p < 0.0001) higher relative to controls and resulted in weight loss in florets treated with the hormetic dose. The antioxidant capacity of florets, measured indirectly as Oxygen Radical Absorbance Capacity (ORAC) and ascorbic acid (AA), decreased in florets exposed to both doses. The concentration of glucobrassicins, aliphatic GLS, and HCA was consistently higher in florets treated with the two doses, compared to non-exposed florets. The enhancement of these compounds was accompanied by the over expression, immediately (6 h) after treatments, of tryptophan N-hydroxylase 2 (CYP79B3), dihomomethionine N-hydroxylase (CYP79F1), and phenylalanine ammonia-lyase (PAL) genes. Overall, the tested doses of H2O2 positively influenced the augmentation of indole-type and aliphatic GLS, as well as HCA in broccoli florets.

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Reductive cyclization of the dichloro compound (I) in the presence of tetrakis(triphenylphosphine)nickel, generated in situ, leads to the formation of the macrocyclic biaryl (II).

The objective of this work was to examine the effect of controlled doses of O3 (0, 5 µL L−1 of O3 for 60 min, and 5 µL L−1 of O3 for 720 min) on the quality and phytochemical content of broccoli florets during postharvest storage. The optimal dose was found at 5 µL L−1 of O3 for 60 min, from the color retention of broccoli florets exposed to the gas treatment. Overall, the antioxidant capacity of the florets was significantly affected by both doses of O3 compared to the non-exposed florets. The profile of glucosinolates was determined for up to 14 days in broccoli florets stored at 4 °C by LC-MS. The amount of total glucobrassicins and total hydroxy-cinnamates in florets significantly (p ≤ 0.05) improved by the application of 5µL L−1 of O3 for 60 min compared to non-treated florets. The up-regulation of genes of the tryptophan-derived glucosinolate pathway was observed immediately after both treatments. The gene expression of CYP79A2 and CYP79B3 in broccoli was significantly higher in broccoli florets exposed to 5 µL L−1 of O3 for 720 min compared to non-exposed florets. Although enhancement of secondary metabolites can be achieved by the fumigation of broccoli florets with low doses of ozone, quality parameters, particularly weight loss, can be compromised.

Broccoli is a vegetable that offers valuable components, such as glucosinolates (GLS), flavonoids, and hydroxycinnamic acids (HCA), for our daily food intake. These substances have been associated with reducing the risk of cancer and cardiovascular diseases (CVD). Broccoli florets are also highly perishable, given their elevated respiration rates and their sensitivity to ethylene. Experiments have been carried out on broccoli to investigate the consequences of abiotic stress post-harvest treatments in retarding the senescence process. Nevertheless, the influence of these treatments on the phytochemicals of broccoli has not been extensively examined. Florets of broccoli (Brassica oleracea) were exposed to an atmosphere consisting of 10,000 µL.L−1 ethanol at room temperature for 30 min and 120 min. The exposure to methyl jasmonate (MeJA) treatments was carried out at room temperature using 1 µL.L−1 for 45 min and 180 min. The yellowing of florets was delayed using 10,000 µL.L−1 of ethanol at both exposure times as compared to untreated florets, and the chlorophyll titers were also superior with both doses over the control. The total phenols of the florets increased by 15% and 18% with the application of the hormetic and high doses, respectively, throughout the storage period compared to unexposed broccoli. The GLS and HCA yields were also increased by both ethanol doses. The exposure of florets to 1 µL.L1 MeJA for 45 min resulted in delayed yellowing of florets; however, longer exposures resulted in yellowing after 21 d and significantly (p < 0.05) increased respiration rates relative to untreated florets. Overall antioxidant capacity of the florets was significantly reduced with both doses of methyl jasmonate; however, HCA titers were increased at both doses. The amount of total glucobrassicins within broccoli was increased following exposure of florets to both doses, but no significant differences in glucoraphanin content were observed. As a conclusion, the ethanol treatment could indeed delay senescence and lead to the induction of phytochemicals. In contrast, MeJA’s effect on quality is not quite substantial; it can, however, be used to improve the phytochemical content of florets, particularly indole-type GLS.

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