Glucosinolate profiling of calepina irregularis

Abstract

Three different types of extracts of volatile isolates from aerial parts of Calepina irregularis (Asso) Thell. were investigated to uncover glucosinolates using indirect methods consisting of either non-enzymatic (thermal degradation) or enzymatic (with exogenous and endogenous myrosinase) hydrolysis, followed by GC-FID/MS analysis of the volatile isolates. The identification of volatile glucosinolate degradation products isolated from C. irregularis indirectly revealed the presence of seven glucosinolates, namely glucoiberverin, glucoiberin, glucocheirolin, glucolepidiin, sinigrin, glucoerucin and glucotropaeolin. Quantitatively the most important compound in the distillate (sample obtained by thermal degradation) was 3-(methylthio)propyl isothiocyanate (95.6%), the degradation product of glucoiberverin, which constituted almost the entire sample. Two isothiocyanates, 3-(methylthio)propyl isothiocyanate (57.8%) and 3-(methylsulfinyl)propyl isothiocyanate (16.7%), originating from degradation of glucoiberverin and glucoiberin, respectively, were the most abundant compounds identified in the hydrolysate (sample obtained by exogenous myrosinase hydrolysis). Some isothiocyanates, 3-(methylthio)propyl isothiocyanate and 3-(methylsulfinyl)propyl isothiocyanate, were present in almost the same percentages (41.0% and 40.0%, respectively), in the autolysate (endogenous myrosinase hydrolysis).