An on-line high performance liquid chromatography-crocin bleaching assay for detection of antioxidants
Bountagkidou, O. ; Klift, E.J.C. van der; Tsimidou, M.Z. ; Ordoudi, S.A. ; Beek, T.A. van - \ 2012
Journal of Chromatography. A, Including electrophoresis and other separation methods 1237 (2012). - ISSN 0021-9673 - p. 80 - 85.
radical scavenging compounds - chemiluminescence detection - natural antioxidants - complex-mixtures - identification - capacity - extracts - inhibition - plant
An on-line HPLC (high performance liquid chromatography) method for the rapid screening of individual antioxidants in mixtures was developed using crocin as a substrate (i.e. oxidation probe) and 2,2'-azobis(2-amidinopropane dihydrochloride (AAPH)) in phosphate buffer (pH 7.5) as a radical generator. The polyene structure of crocin and AAPH-derived peroxyl radicals resemble the lipidic substrates and radicals found in true food more closely than the popular, albeit artificial, DPPH (1,1-diphenyl-2-picrylhydrazyl) and ABTS+ (2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonate)) do. After separation by a C18 (octadecyl silica) column and UV (ultraviolet) detection, antioxidative analytes react with peroxyl radicals at 90 °C and the inhibition of crocin oxidation (i.e. bleaching) is detected as a positive peak by an absorbance detector at 440 nm. The method is simple, uses standard instruments and inexpensive reagents. It can be applied for isocratic HPLC runs using mobile phases containing 10–90% organic solvent in water, weak acids or buffers (pH 3.5–8.5). With baseline correction, gradient runs are also feasible. The radical scavenging activity of several natural antioxidants and a green tea extract was studied. After optimisation of conditions such as reagent concentrations and flows, the limit of detection varied from 0.79 to 7.4 ng, depending on the antioxidant. --------------------------------------------------------------------------------
Syringa oblata Lindl var. alba as a source of oleuropein and related compounds
Nenadis, N. ; Vervoort, J.J.M. ; Boeren, J.A. ; Tsimidou, M.Z. - \ 2007
Journal of the Science of Food and Agriculture 87 (2007)1. - ISSN 0022-5142 - p. 160 - 166.
radical scavenging activity - olea-europaea leaves - phenolic-compounds - antioxidant activity - liquid-chromatography - olive oil - hydroxytyrosol - glucosides
The leaf methanol extract of Syringa oblata Lindl var. alba was investigated as a source of oleuropein and related compounds. The extract had a high total phenol content and a radical scavenging activity similar to that of the respective extract from Olea europaea leaves. HPLC-DAD characterisation of the two most abundant phenolic compounds in the extract of S. oblata indicated that both had UV spectra matching that of oleuropein. The presence of oleuropein was verified by using LC-MS. Identification of the second compound was only feasible after isolation (preparative HPLC) and spectroscopic characterisation [LC-MS, 1H NMR and homonuclear two-dimensional correlated spectroscopy (COSY)]. The compound identified was the known bioactive syringopicroside. On the basis of MS data other peaks were assigned to oleuropein aglycone, verbascoside, ligstroside and syringopicroside derivatives, as well as to a luteolin rutinoside. The findings are promising for the potential exploitation of S. oblata leaf extract as a source for oleuropein and other bioactive ingredients