Preharvest Methyl Jasmonate Treatment Increased Glucosinolate Biosynthesis, Sulforaphane Accumulation, and Antioxidant Activity of Broccoli

Abstract

Broccoli is becoming increasingly popular among consumers owing to its nutritional value and rich bioactive compounds, such glucosinolates (GSLs) and hydrolysis products, which are secondary metabolites for plant defense, cancer prevention, and higher antioxidant activity for humans. In this study, 40 μmol/L methyl jasmonate (MeJA) was sprayed onto broccoli from budding until harvest. The harvested broccoli florets, stem, and leaves were used to measure the contents of GSLs, sulforaphane, total phenolics, and flavonoids, as well as myrosinase activity, antioxidant activity, and gene expression involved in GSL biosynthesis. The overall results revealed that GSL biosynthesis and sulforaphane accumulation were most likely induced by exogenous MeJA treatment by upregulating the expression of CYP83A1, SUR1, UGT74B1, and SOT18 genes. Exogenous MeJA treatment more remarkably contributed to the increased GSL biosynthesis in broccoli cultivars with low-level GSL content (Yanxiu) than that with high-level GSLs (Xianglv No.3). Moreover, MeJA treatment had a more remarkable increasing effect in broccoli florets than stem and leaves. Interestingly, total flavonoid content substantially increased in broccoli florets after MeJA treatment, but total phenolics did not. Similarly, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity, trolox-equivalent antioxidant capacity (ABTS), and ferric-reducing antioxidant power (FRAP) were higher in broccoli floret after MeJA treatment. In conclusion, MeJA mediated bioactive compound metabolism, had positive effects on GSL biosynthesis, sulforaphane, and flavonoids accumulation, and showed positive correlation on inducing higher antioxidant activities in broccoli floret. Hence, preharvest supplementation with 40 μM MeJA could be a good way to improve the nutritional value of broccoli florets.

Preharvest Methyl Jasmonate Treatment Affects the Mineral Profile, Metabolites, and Antioxidant Capacity of Radish Microgreens Produced without Substrate

“…The results revealed that the preharvest MeJA treatment resulted in a significant increase in the antioxidant capacity of radish microgreens across all cultivars. Similar findings were reported by Wang et al [ 9 ] in a study of two cultivars of broccoli florets, where MeJA treatment also showed a remarkable increase in antioxidant capacity. Among the radish microgreens, ‘Asia purple’ treated with 1.0 mM MeJA exhibited the highest antioxidant activity, and ‘Koregon red’ showed the second highest in all assays when the sample concentrations were 1 and 2.5 mg mL −1 ( Table 4 ).…”

“…This observation highlights the potential of 1.0 mM MeJA treatment to enhance the accumulation of these specific GSLs. A previous study on chives showed the dose-dependent effects of preharvest MeJA treatment on secondary metabolites [ 9 ], and 0.5 mM MeJA had the most significant effect, specifically on phenolic compounds of substrate-grown chives.…”

“…Microgreens have attracted attention due to their short growing cycle, efficient utilization of space, vibrant colors, diverse flavors, and rich phytonutrients [ 7 , 8 ]. Microgreens and sprouts from the Brassicaceae family, particularly radish ( Raphanus sativus L.), contain significant amounts of antioxidants, vitamin C, and health-promoting compounds such as glucosinolates (GSLs) and phenolic compounds and have been shown to have antioxidant and anticancer properties, both in vivo and in vitro [ 7 , 9 ].…”

“…In contrast to JA, which cannot easily penetrate the cell membrane, MeJA can be transmitted via air and penetrate the cell membrane due to its high volatility [ 11 ]. The JA-induced plant’s defense mechanisms primarily involve the activation of antioxidative enzymes and bioactive phytochemical compounds [ 13 , 14 ], which enhances the medicinal and nutritional values of plants [ 9 ]. Therefore, factors affecting phytochemical content and profile in the production of Brassicaceae plants are valuable considerations for both plant and human health [ 14 ].…”

Chromosome-scale reference genome of broccoli (Brassica oleracea var. italica Plenck) provides insights into glucosinolate biosynthesis

“…According to a previously described method [ 80 ], GSLs were extracted and quantified using the following steps. Briefly, the freeze-dried sample powder was soaked in 70% methanol with 100 μl of sinigrin (5 mmol/l, internal standard) for 20 min in a 75°C water bath, the cooling mixture added with barium acetate and then for centrifugation.…”