This effect of gluconasturtiin is due to its degradation by the plant enzyme myrosinase into phenethyl isothiocyanate, which is toxic to many organisms.

[2] The compound was first reported in 1899, after its isolation from watercress, Nasturtium officinale, and the cress Barbarea verna.

[1]: Section 2  Gluconasturtiin is now known to occur widely in other brassica families including Brassicaceae and Resedaceae.

The enzyme myrosinase removes the glucose group in gluconasturiin to give an intermediate which spontaneously rearranges to phenethyl isothiocyanate.

[7] At concentrations typically found in foods, the glucosinolates are not toxic to humans and can be useful flavor components.