-
[show abstract]
[hide abstract]
ABSTRACT: ABTS and FRAP post-column techniques evaluate the antioxidant characteristics of HPLC separated compounds with specific reagents. ABTS characterize their ability to scavenge free radicals by electron-donating antioxidants, resulting in the absorbance decrease of the chromophoric radical. FRAP - is based on the reduction of Fe(III)-tripyridyltriazine complex to Fe(II)-tripyridyltriazine at low pH by electron-donating antioxidants, resulting in an absorbance increase. Both post-column assays were evaluated and compared according to the following validation parameters: specificity, precision, limit of detection (LoD), limit of quantitation (LoQ) and linearity. ABTS and FRAP post-column assays were specific, repeatable and sensitive and thus can be used for the evaluation of antioxidant active compounds. Antioxidant active compounds were quantified according to TEAC for each assay and ABTS/FRAP ratio was derived. No previous records of antioxidative activity of leaves and fruits of strawberries (Fragaria viridis, Fragaria moschata) research have been found. The research results confirm the reliability of ABTS and FRAP post-column assays for screening of antioxidants in complex mixtures and the determination of radical scavenging and ferric reducing ability by their TEAC values.
Journal of chromatography. A 02/2012; 1233:8-15. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In Lithuania, two species of the genus Fragaria L. (Rosaceae), F. vesca L. and F. viridis Weston, occur naturally in the wild and two others, F. moschata Weston and F. × ananassa Duchesne ex Rozier are found escaped from cultivation. The main objective of this study was to establish the variation pattern in the content of chlorogenic acid, rutin and hyperoside in leaves and fruits of the native Lithuanian species. In this work, the chemical polymorphisms of different Fragaria species were studied by growing plants side by side under the same cultivated field conditions. F. vesca fruits had the highest rutin (1.38 ± 0.19 mg g (- 1) DM), hyperoside (0.69 ± 0.10 mg g(-1) DM) and chlorogenic acid (2.25 ± 0.34 mg g(-1) DM) content, followed by F. viridis and F. moschata. Our results showed that the leaves should be taken into account as important rutin and hyperoside contributors for strawberries.
Natural product research 02/2012; · 1.01 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: On-line method, which combines HPLC distribution and post-column reaction, was designed for the search of individual antioxidants. Optimization of the assay was performed evaluating optimal ABTS(+) radical cation concentration in the reactor, reaction time, impact of flow rate, reaction coil length. HPLC-ABTS assay validation in this work was performed by assessing reference antioxidant negative peak areas in radical scavenging chromatogram. Sample free radical scavenging activity is expressed as trolox equivalent antioxidant capacity (TEAC). Optimized and validated method was applied in detection of compounds possessing free radical scavenging ability in complex mixtures. Antioxidant compounds were studied in perilla (Perilla frutescens (L.) Britton var. crispa f. viridis) herbal raw material and its preparations. The HPLC-separated antioxidant compounds were identified using HPLC-photodiode array coupled to mass spectrometer, using a reference mass for determining accurate masses. Radical scavenging characteristics of rosmarinic acid, which is the dominant phenolic compound in medicinal herbal raw material of perilla and its preparations, were confirmed by the calculated TEAC values. Compounds responsible for antioxidant effect in herbal raw materials and herbal preparations were identified, evaluated and compared.
Journal of chromatography. A 10/2010; 1217(49):7690-8. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The most important attention is paid to the search of natural antioxidants and their evaluation in medicinal and food raw materials of plant origin. A number of plants, their extracts, food products, and medicinal preparations appear to be the objects of scientific research. Effectiveness and informative character of research, undoubtedly, depend on relevance, sensitivity, and efficiency of the methods chosen. The aim of this work was to develop and validate the postcolumn high-performance liquid chromatography (HPLC)-DPPH method as well as its application in the evaluation of antioxidant activity of known and unknown compounds scavenging free radicals and existing in medicinal plant raw materials. HPLC-separated compounds were identified at the wavelength of 275 nm, and then the mobile phase with analytes flowed through a mixing tee to the reaction coil, where DPPH reagent solution was supplied. The solution flow rate was 0.4 mL/min. The reaction coil was connected with UV/VIS type detector, which measured absorption of flowing solution at the wavelength of 520 nm. It was determined that vitexin rhamnoside, the dominant compound in the leaves of Crataegus monogyna, was not a significant radical scavenger. The most active antioxidant in the leaves and flowers of Crataegus monogyna was chlorogenic acid. The most active antioxidant in Origanum vulgare raw material was rosmarinic acid. Identified analytes in the extracts of Achillea millefolium that possessed radical-scavenging properties were chlorogenic acid, luteolin-7-O-glucoside, rutin, and luteolin.
Medicina (Kaunas, Lithuania) 02/2009; 45(5):382-94. · 0.42 Impact Factor
-
Journal of chromatography. A 10/2000; 1217(49-1217):7690-8. · 4.19 Impact Factor
