Exogenous sodium nitroprusside treatment of broccoli florets extends shelf life, enhances antioxidant enzyme activity, and inhibits chlorophyll-degradation

The effect of an exogenous application of sodium nitroprusside (SNP) on the shelf life, antioxidant enzyme and chlorophyll-degrading enzyme activity, and chlorophyll-degradation related gene expression was investigated in stored broccoli. The preliminary results indicated that the 200 mu mol L-1 SNP treatment had the greatest effect on extending shelf life of broccoli florets so this concentration was used in the remainder of the study. The SNP treatment delayed chlorophyll degradation, thus color was maintained and shelf-life was extended. The activity of the antioxidant enzymes, catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) was all enhanced while glutathione reductase (GR) activity was inhibited throughout the storage. Relative to the untreated control, the SNP treatment suppressed the activity of the chlorophyll-degrading enzymes, chlorophyllase (Chlase), chlorophyll degrading peroxidase (Chl-PDX), Mg-dechelatase (MD), and pheophytinase (PPH), and also suppressed chlorophyllase I (BoCHL1), chlorophyllase II (BoCHL2), chlorophyllase III (BoCLH(3)) and pheophorbide a oxygenase (BoPAO) gene expression during the entire storage period. In summary, 200 mu mol L-1 SNP treatment of broccoli extends shelf life, enhances oxidative stress tolerance by enhancing the activity of antioxidant enzymes, and inhibits the activity of chlorophyll-degrading enzymes and related gene expression. The combined effect delayed the yellowing of broccoli florets by inhibiting chlorophyll degradation, thus extending the shelf life of broccoli florets. (C) 2016 Published by Elsevier B.V.