Determination of glucosinolates in broccoli-based dietary supplements by cyclodextrin-mediated capillary zone electrophoresis

• Published in: Journal of food composition and analysis Vol. 78; pp. 138 - 149
• Main Authors: Lechtenberg, Matthias, Hensel, Andreas
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-05-2019
• Subjects: Broccoli; Capillary electrophoresis; Dietary supplement; Food analysis; Food composition; Food supplement; Glucoraphanin; Glucosinolate; Sulforaphane; Glucosinolate; neo-GB; Food analysis; BBDS; SI; Sulforaphane; SFN; Food composition; GRe; GB; Glucoraphanin; EOF; GE; Food supplement; GSL; Dietary supplement; CE; GI; Capillary electrophoresis; GN; GR; GT; 4OH-GB; CZE; Broccoli; ITC
• ISSN: 0889-1575; 1096-0481
• DOI: 10.1016/j.jfca.2019.02.007

•Cyclodextrin-mediated capillary zone electrophoresis is a valuable technique for the separation and quantification of glucosinolates.•The possibility to easily modify and adapt selectivity on demand is a unique feature of capillary electrophoresis.•Controlled variation of temperature and β-cyclodextrin concentration provide a set of methods with customized selectivities.•Fingerprint electropherograms are appropriate quality markers for broccoli-based dietary supplements.•Quantitative analysis of 14 broccoli-based dietary supplements showed remarkable differences in quality.
A new cyclodextrin-mediated capillary zone electrophoresis method for the separation and quantification of intact glucosinolates (GSL) has been developed. β-Cyclodextrin concentration and temperature were shown to be key parameters for selectivity. Controlled variation of both parameters provided a set of methods for the analysis of GSL-containing plants with customized selectivities. As a proof of concept, parameters were adapted for the analysis of broccoli-based dietary supplements (BBDS) obtained from different sources. All main GSL (glucoraphanin, -iberin, -erucin, and 4-hydroxyglucobrassicin) – which typically occur in broccoli plants at early development stages – were successfully analyzed using a 100 mM borate buffer with 1% β-cyclodextrin at 20 °C.
Analysis of BBDS showed unexpected results. In most cases, supplements had been specified to contain seeds, sprouts or young broccoli plants. In many cases, results did not reflect the description on the label. Several samples apparently contained broccoli from older plant development stages, marked by higher amounts of indole-derived GSL and very low concentrations of aliphatic GSL. Considerable amounts of non-broccoli GSL were detected in two samples: sinalbin and a mixture of 3-butenyl- and 4-pentenylglucosinolate. No glucosinolates were detectable in two further samples. In total >50% of all investigated samples did not meet the specifications.