|KARCHER, ARRON - OKLAHOMA STATE UNIVERSITY
|EL RASSI, ZIAD - OKLAHOMA STATE UNIVERSITY
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/1999
Publication Date: N/A
Interpretive Summary: The fungus that causes sclerotinia blight disease of peanut produces black bodies (sclerotia) as a mechanism of survival in field soil. Under suitable environmental conditions, infection structures are formed on the germinating sclerotia that are capable of starting infection on peanut plants. Earlier research in our laboratory has shown that applying green manure and rapeseed from the rape plant (cabbage family) to the soil have the potential to reduce the viability of the sclerotinia blight fungus under controlled environmental conditions. The active ingredients in rape greens and rapeseed are called glucosinolates . Glucosinolates break down in wet soil, producing toxic fumigants that limit the growth of the sclerotinia fungus and other fungi. To further study the effects of these compounds on soil organisms, methods need to be developed to determine the concentration of glucosinolates from the various rape variety sources. This spaper reports on the development of an analytical method to determine the concentration of glucosinolates based on separation in capillary tubing and attaching with fluorescent dye to allow their sensitive detection by laser. The higher the glucosinolates in a given rape variety, the higher concentration of volatile compounds released in the soil environment which might contribute to reducing the viability of the fungal sclerotia, and thus reducing fungal infection. This technique is useful to scientists and food chemists who are interested in a sensitive method for determining the concentration of glucosinolates in plants.
Technical Abstract: A capillary electrophoresis (CE) method was developed for the profiling and determination of individual glucosinolates (GSs) via their isothiocyanate degradation products upon myrosinase digestion. The resulting isothiocyanates, the structures of which are reflective of the parent GSs, were then converted to their corresponding amines via base hydrolysis or reaction with 1,2-benzenedithiol. Subsequently, the amines were fluorescently labeled to allow their sensitive detection by laser-induced fluorescence (LIF). The CE method involved the use of in situ charged micelles for the separation of isothiocyanates and their corresponding fluorescently labeled amines by micellar electrokinetic capillary chromatography (MECC). The term "in situ charged micelles" refers to micelles formed by comlexing the polar hydroxyl groups of glycosidic surfactants with borate. The MECC method with on-column LIF detection was applied to the determination of GSs in white cabbage, rapeseed leaves, and rapeseed roots.