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Title: HIGH PERFORMANCE LIQUID PHASE SEPARATION OF GLYCOSIDES. III. DETERMINATION OF TOTAL GLUCOSINOLATES IN CABBAGE AND RAPESEED BY CAPILLARY ELECTROPHORESIS VIA THE ENZYMATICALLY RELEASED GLUCOSE

Author
item KARCHER, ARRON - OKLAHOMA STATE UNIVERSITY
item Melouk, Hassan
item EL RASSI, ZIAD - OKLAHOMA STATE UNIVERSITY

Submitted to: Analytical Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The fungus that causes sclerotinia blight of peanut produces black bodies (sclerotia) as a mechanism of survival in field soil. Fungal infection structures (capable of infecting peanut plants) are produced upon germination of the sclerotia. Green manure from the rape plant (cabbage family) was incorporated in the top 4 inches of soil as a sclerotinia management strategy. Rape greens contain glucosinolates that upon breakdow in soil produce volatile compounds with biocidal activity (toxic fumigants) that have the potential to reduce the viability of sclerotia of the blight fungus. Methods are needed to determine the concentration of glucosinolates from various rape varieties after incorporation into the soil. This paper reports on the development of an accurate and sensitive technique based on separation in capillary tubing which is useful in determining the concentration of glucosinolates from rape plants and other plant members of fthe cabbage family. The higher the glucosinolates in a given rape variety, the higher volatile concentration will be released in the soil environment that in turn will reduce the viability of the fungal sclerotia.

Technical Abstract: A selective and sensitive method for the determination of total glucosinolates (GS's) in plant extracts by capillary electrophoresis-laser induced fluorescence (LIF) detection was developed. It was based on the enzymatically released glucose from glucosinolates in the presence of the hydrolyzing enzyme myrosinase. The released glucose was converted to gluconic acis (GA) by the action of glucose oxidase. The resulting GA was then labeled selectively with the fluorescent tag 7-aminonaphthalene-1,3- disulfonic acid (ANDSA). The peak area resulting from the GA-ANDSA derived from free and bound glucose was subtracted from the peak area of the GA- ANDSA resulting from the free glucose in the sample. This gave the total glucosinolates in the sample. The peak areas were normalized to the internal standard N-acetylneuraminic acid derivatized with ANDSA. The method was validated using four different plant extracts of white cabbage leaves, rapeseed leaves, rapeseed roots, and rapeseed seeds. Furthermore, capillary electrophoresis-UV detection method for profiling GS in plant extracts was developed. In addition to providing a fingerprint of the glucosinolates in plant extracts, the method allowed the experimenter to rapidly check the various steps involved in the extraction and sample clean-up.