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. --------------------------------------------------------------------------------
Isolation of antioxidative secoiridoids from olive wood (Olea europaea L.) guided by on-line HPLC-DAD-radical scavenging detection
Pérez-Bonilla, M. ; Salido, S. ; Beek, T.A. van; Waard, P. de; Linares-Palomino, P.J. ; Sánchez, A. ; Altarejos, J. - \ 2011
Food Chemistry 124 (2011)1. - ISSN 0308-8146 - p. 36 - 41.
liquid-chromatography - natural antioxidants - jasminum polyanthum - phenolic-compounds - mill wastewaters - by-products - glucosides - identification - extracts - plants
The woody portion of olive tree pruning is a source of natural antioxidants of potential interest for the food industry. This work deals with the isolation and identification of further antioxidants present in an ethyl acetate extract of olive (Olea europaea L.) wood. Thus, a new secoiridoid, oleuropein-3¿-methyl ether (1), together with six known secoiridoids, 7¿S-hydroxyoleuropein (2), jaspolyanoside (3), ligustroside 3'-O-ß-d-glucoside (4), jaspolyoside (5), isojaspolyoside A (6) and oleuropein 3'-O-ß-d-glucoside (7) were isolated by combining HPLC with fast on-line post-column radical scavenging activity evaluation. The structures of these compounds were determined by spectroscopic methods. The antioxidant activity of the pure compounds was determined by measuring the radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). Compounds 2, 5 and 7 displayed a higher antioxidative effect than the synthetic antioxidant BHT and lower than rosmarinic acid, whereas compounds 3 and 4 showed weak DPPH scavenging activity.
Antioxidant properties of differently processed spinach products
Castenmiller, J.J.M. ; Linssen, J.P.H. ; Heinonen, I.M. ; Hopia, A.I. ; Schwarz, K. ; Hollman, P.C.H. ; West, C.E. - \ 2002
Nahrung - Food 46 (2002)4. - ISSN 0027-769X - p. 290 - 293.
low-density-lipoprotein - natural antioxidants - alpha-tocopherol - methyl linoleate - total phenolics - red wine - vegetables - capacity - fruits - common
The effect of variously processed spinach products (whole-leaf, minced and enzymatically liquefied spinach) on lipid oxidation was determined. In an autoxidative methyl linoleate (MeLo) system the inhibition of hydroperoxide formation, measured by HPLC after three days of oxidation, was in descending order: whole-leaf > liquefied > minced spinach. The inhibition of formation of thiobarbituric acid-reactive substances (TBARS) and hexanal by spinach was determined in cooked meatballs with added spinach after two days of storage at 4°C. The formation of TBARS was inhibited by liquefied spinach at 200 g/kg meat; all other spinach products tested at 100 and 200 g/kg were pro-oxidative. The formation of hexanal was inhibited by both minced and liquefied spinach at 100 and 200 g/kg meat. The variously processed spinach products behaved differently when tested for their antioxidant activity (MeLo) or oxidative stability (meatballs). We conclude that the effect of spinach products on lipid oxidation is affected by processing
Screening of Plant Extracts for Antioxidant Activity: a Comparative Study on Three Testing Methods
Koleva, I. ; Beek, T.A. van; Linssen, J.P.H. ; Groot, Æ. de; Evstatieva, L.N. - \ 2002
Phytochemical Analysis 13 (2002)1. - ISSN 0958-0344 - p. 8 - 17.
performance liquid-chromatography - radical-scavenging activity - tea aspalathus-linearis - natural antioxidants - oxidative stability - methyl linoleate - alpha-tocopherol - phenolic-acids - vegetable-oils - beta-carotene
Three methods widely employed in the evaluation of antioxidant activity, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging method, static headspace gas chromatography (HS-GC) and -carotene bleaching test (BCBT), have been compared with regard to their application in the screening of plant extracts. The strengths and limitations of each method have been illustrated by testing a number of extracts, of differing polarity, from plants of the genus Sideritis, and two known antioxidants (butylated hydroxytoluene and rosmarinic acid). The sample polarity was important for the exhibited activity in the BCBT and HS-GC methods but not for the DPPH method. The complex composition of the extracts and partition phenomena affected their activity in each assay. The value of the BCBT method appears to be limited to less polar samples. Although slow, the HS-GC method is preferable for assessing the antioxidant inhibitory properties on the formation of unwanted secondary volatile products. Being rapid, simple and independent of sample polarity, the DPPH method is very convenient for the quick screening of many samples for radical scavenging activity.