Optimization of Methyl Jasmonate Application to Broccoli Florets to Enhance Health-promoting Phytochemical Content.

BACKGROUND
Spray treatment of methyl jasmonate (MeJA) has been shown to increase glucosinolate (GS) concentrations and health promoting activity in Brassica vegetables. Since there is no reported standardized protocol, we have conducted several MeJA treatment studies to maximize human health bioactivity using the F1 broccoli cultivar 'Green Magic'.

RESULTS
Foliar MeJA application four days prior to harvest of broccoli at commercial maturity resulted in enhanced total GS concentrations. Although a single application of 250 µM MeJA maximized GS concentration in broccoli florets, two days of consecutive treatments (four and three days prior to harvest) of 250 µM MeJA further enhanced neoglucobrassicin concentrations and floret extract quinone reductase (QR) inducing activity. With increasing concentrations of MeJA in spray applications to broccoli florets, concentrations of the glucosinolates glucoraphanin, gluconasturtiin, neoglucobrassicin, and the isothiocyanate, sulforaphane and anti-cancer and anti-inflammatory bioactivity as measured by QR induction and inhibition of nitric oxide (NO) production, respectively were significantly increased. Concentrations of these phytochemicals showed strong positive correlations with QR induction and NO inhibitory activity.

CONCLUSIONS
These application protocols were found to maximize GS and GS hydrolysis product concentrations and putatively enhance the health promoting properties of broccoli heads for consumers.