Nutraceutical Value of Woad (Isatis tinctoria) Flower Buds of Ecotypes from Sicily, Italy

Woad (Isatis tinctoria L.) is a wild plant widely diffused throughout Europe,Italy included. In ancient times it was exploited as a dye-plant, to obtain the indigocolour. Recently woad was rediscovered also for its cosmetic and anti-inflammatoryproperties. Belonging to Brassicaceae family, woad contains glucosinolates, which areprecursor of isothiocyanates, which possess chemopreventive antioxidant properties.Although woad is not considered as an edible vegetable worldwide, rural people livingaround Mount Etna in Sicily, Italy, are accustomed to collect the flower buds fromwild plants in the late winter, to be consumed after boiling as ingredients for salads oromelets. To investigate the nutraceutical value of woad, fresh flower buds werecollected on Mount Etna slopes in Sicily over two years and analysed for their bioactivecompound content. Woad samples contained considerable amounts of glucosinolates,ranging from 80 up to over 100 μmol/g d.w., which are values higher than thosefound in other Brassica vegetables. Only gluconapin and the most interesting glucobrassicin,which is the natural precursor of indole-3-carbinol, a multiple antitumorigeniccompound, were found. High mean values were also recorded for totalpolyphenols and flavonoids (25 GAE mg/g d.w. and 7 CE mg/g d.w., respectively).Consequently, also the antioxidant activity (H-ORAC) of the woad flower budsresulted among the highest reported for other Brassica vegetables, being about 300μmol TE/g d.w. Since processing can partly reduce the glucosinolate content ofvegetables, different cooking ways, such as boiling and microwaving, were compared.Boiling for 10 min caused losses of 34% of total glucosinolates, while microwaving (10min, 800 W) only reduced the glucosinolate amount by 3%. The results obtainedsuggest that woad flower buds could be considered as a functional food with possiblechemopreventive properties.