The mechanism of deterioration of the glucosinolate-myrosynase system in radish roots during cold storage after harvest

- Major isothiocyanates in radish roots are raphasatin (RH) and sulforaphene (SFE).
- The levels of these beneficial compounds decrease during cold storage after harvest.
- We first tried to clear the cause of RH and SFE reduction of harvested radish roots.
- The decrease of SFE comes from the deterioration of the glucosinolate­myrosinase system.
- The deterioration is caused by the reduction of myrosinase activity and ascorbate content.

The hydrolysis of glucosinolates (GSLs) by myrosinase yields varieties of degradation products including isothiocyanates (ITCs). This process is controlled by the glucosinolate­myrosinase (G-M) system. The major ITCs in radish roots are raphasatin and sulforaphene (SFE), and the levels of these compounds decrease during storage after harvest. We investigated the G­M system to understand the mechanism behind the decrease in the ITCs in radish roots. Six varieties of radish roots were stored for 8 weeks at 0-1.5 °C. The concentrations of GSLs (glucoraphasatin and glucoraphenin) were maintained at harvest levels without significant changes during the storage period. However, SFE concentration and myrosinase activity remarkably decreased for 8 weeks. Pearson correlation analysis between ITCs, GSLs, and myrosinase activity showed that a decrease of SFE during storage had a positive correlation with a decrease in myrosinase activity, which resulted from a decrease of ascorbic acid but also a decrease of myrosinase activity-related gene expressions.