15C-1 |
Analysis of flavonol glycosides in almond seedcoats by MALDI-TOF MS |
S. FRISON-NORRIE and P. Sporns. Dept. of Agricultural, Food, & Nutritional Science, Univ. of Alberta, Edmonton, AB T6G 2P5, Canada Flavonol glycosides are thought to confer certain health benefits by virtue of their antioxidant properties. Furthermore, the types and relative amounts of flavonol glycosides in any plant are distinctive. The most common method of flavonol glycoside analysis is high performance liquid chromatography (HPLC). However, this technique can take up to an hour for one sample run, and requires standards for identification. Conversely, one analysis using matrix-assisted laser desorption/ionization (MALDI-TOF MS) can be performed in 1-2 minutes, and offers direct access to molecular weight. We have chosen almond seedcoats (Prunus amygdalus) as a model to test the validity of MALDI-TOF MS quantitative methodology. Our objective was to develop a reliable MALDI-TOF MS methodology for qualitative and quantitative analysis of flavonol glycosides in almond seedcoats. MALDI-TOF MS analysis was conducted using 2',4',6'-trihydroxyacetophenone monohydrate as a matrix. Quantification was performed using rutin (quercetin-3-rutinoside) as an internal standard. Response factors for each aglycone type were determined. As well, correction factors were calculated to adjust for fragmentation of the carbohydrate moieties in the mass spectrometer. Results were compared to HPLC analysis. Our results indicated four previously unreported flavonol glycosides in the almond seedcoat sample. Isorhamnetin-3-rutinoside, isorhamnetin-3-glucoside, kaempferol-3-rutinoside, and kaempferol-3-glucoside were identified by MALDI-TOF MS at concentrations of 51(5) mg/g, 25(3) mg/g, 18(3) mg/g, and 8(1) mg/g, respectively, on a fresh weight basis. (Standard deviations are indicated in parentheses). These concentrations were similar to those determined by HPLC. These results suggest that the MALDI-TOF MS technique is an excellent complement to conventional analytical methods. As such, MALDI-TOF MS has the potential to be used as a rapid and definitive screening tool for a wide variety of almond samples. This capability is significant for exploring varietal differences and evaluating the authenticity of processed samples. Furthermore, determination of possible bioactive components in almond seedcoats may improve their commercial value.
Session 15C, Food Chemistry: Food composition and analysis
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