The 2012 ASHS Annual Conference

Previous research has shown that methyl jasmonate (MeJA) treatment increases the concentration of phenolics in radish and broccoli sprouts but has no effect in broccoli florets. This suggests that MeJA enhances phenolic concentrations in the vegetative tissues of brassica vegetables. To test this hypothesis, two kale cultivars, ‘Dwarf Blue Curled Vates’ and ‘Red Winter’ were sprayed with 0, 50, 250, and 500 µM MeJA four days prior to the harvest of apical and basal leaves from treated and control plants grown in the field during the summers of 2010 and 2011. Three replicate samples in each year were assayed for glucosinolates and flavonoid concentrations by HPLC and total phenolic concentration by the Folin-Ciocalteu assay. Antioxidant activity of 70% methanol extracts were also quantified using the 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. Two hundred and fifty (250) µM MeJA maximized glucobrassicin and neoglucobrassicin in apical leaves of both ‘Red Winter’ and ‘Dwarf Blue Curled Vates’. MeJA treatment significantly increased total phenolics and flavonoids in both cultivars in 2010. In contrast, no significant increase in total phenolic and flavonoid concentrations was observed in 2011 with any of the MeJA treatments, suggesting a year by treatment interaction. ABTS and DPPH antioxidant assays significantly correlated with total phenolics (r = 0.96, P < 0.001 and r = 0.81, P < 0.001, respectively). MeJA treatments can positively enhance health promoting bioactivity of kale by increasing indole glucosinolate concentrations. Antioxidant activity in kale is closely associated with total phenolic concentrations and can be enhanced by MeJA treatments depending on environmental conditions.