Analysis of oilseed glucosinolates and their fate during pressing or dehulling

Abstract

Brassica carinata (A.) Braun and Camelina sativa (L.) Crantz are two re-emerging oilseed crops of the Brassicaceae family that are being adapted for cultivation in western Canada. Both seeds of these species reportedly accumulate considerable amounts of sulfur-containing secondary metabolites called glucosinolates. The purpose of the current work was to gain knowledge of the occurrence and distribution of glucosinolates during primary processing of these oilseeds, including during pressing and dehulling. In the first study, a reversed phase HPLC method was developed for the analysis of sinigrin, the major glucosinolate in B. carinata. Both C18 columns selected were able to separate the compound with an isocratic eluent containing 100% tetramethylammonium bromide (10 mM, pH 5) delivered at 1 mL/min at a column temperature of 25oC. These chromatographic conditions were applied and sinigrin concentration of whole B.carinata seed was estimated to be 29 μg/mg. Average matrix effect was estimated to be 104% that was caused by other components in the B. carinata seed matrix. In the second study, high concentrations of glucosinolates were detected and identified in fractions of C. sativa seeds using HPLC-ESI-MS. Methods for extraction, isolation, and purification of three individual glucosinolates from these fractions are reported. Quantitation of total glucosinolates was performed on proton NMR using DMF as an internal standard. Quantitation of individual glucosinolates was achieved by using MS extracted ion chromatogram data. Total glucosinolates were found in C. sativa whole seed at a concentration of 14 μg/mg, and glucocamelinin, the major glucosinolate, constituted 65% of the total amount. In addition, a dehulling treatment was applied to C. sativa seeds, from which both oil content and crude protein content increased after dehulling of the seeds.