15B-2 |
Capillary electrophoresis analysis of limonoid glucosides and phlorin in citrus processing residues |
R. J. BRADDOCK, Citrus Research & Education Center, Univ. of Florida, 700 Experiment Station Rd., Lake Alfred, FL 33850 and C. R. Bryan. The supposed pharmacological activity of limonin glucoside (LG) from citrus tissues has created interest in extraction and HPLC analysis. Phlorin is a potential HPLC adjunct to detect juice adulteration. Isolation and analysis by capillary electrophoresis (CE), rather than HPLC, may exploit the water solubility of LG and phlorin, offering an alternative analytical technique. The objective was to extract LG and phlorin from citrus tissues with water and establish a CE method for analysis. LG and phlorin were extracted from citrus fruit tissues and assayed by CE. Sources for LG were orange processing residues, 50 °Brix citrus molasses and grapefruit seeds; while phlorin was isolated from orange residue. LG extraction was achieved by extracting with various concentrations of ethanol, methanol and water, then purification and resin (XAD-16) concentration to obtain pure compound. The maximum amount of LG was extracted with 25% ethanol from processing residue (2.9 ± 0.1mg/g dried peel)=water extraction (2.6 ± 0.2) > 100% methanol (1.40 ± 0.08) > 95% ethanol (1.30 ± 0.04). Water extraction of LG and phlorin required small amounts of pectinase to reduce viscosity and foaming. CE analysis did not require purification beyond filtration or transfer to an organic solvent, as required for HPLC. CE resulted in migration of LG and phlorin as anions represented as distinct peaks in electropherograms containing other citrus flavonoids and limonoid glucosides. The pKa of phlorin was estimated by CE to be ca. 8.0; while LG was anionic down to pH 5.0. CE is a good analytical technique for the study of LG and phlorin, allowing high resolution, rapid separations and minimum sample preparation. This study also provided information regarding extraction and purification of these compounds. Concentrations of LG and phlorin in citrus substrates are too low for economic commercial recovery.
Session 15B, Citrus
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