A new antimicrobial glucosinolate autolysis product, 4-isothiocyanatobutanoic acid, from the diffuse wallflower (Erysimum diffusum): Methyl 4-isothiocyanatobutanoate, a long unrecognized artifact of the isolation procedure?

A GC–MS analysis of Erysimum diffusum Ehrh. (Brassicaceae) glucosinolate autolysis products led to the identification of a new mustard oil constituent – 4-isothiocyanatobutanoic acid. The identity of the new glucosinolate breakdown product was confirmed by means of co-injection of the synthetic compound in the GC with the root autolysate and derivatization reaction to the well known methyl ester. Methyl ester of this acid was long believed to be a genuine glucosinolate hydrolysis product but we now provide evidence that it could be an artifact of the isolation procedure. 4-Isothiocyanatobutanoic acid was assayed for antimicrobial activity and demonstrated significant inhibitory (10–220 μg/ml) and microbicidal (10–1175 μg/ml) activity against important human pathogens.

► New mustard oil constituent, 4-isothiocyanatobutanoic acid from Erysimum diffusum.
► Methyl ester of this acid was shown to be the artifact of the isolation procedure.
► The acid is an antimicrobial agent with MIC values of 10–220 μg/ml.