Spectrophotometric Determination of Phenolic Antioxidants in the Presence of Thiols and Proteins
نویسندگان
چکیده
Development of easy, practical, and low-cost spectrophotometric methods is required for the selective determination of phenolic antioxidants in the presence of other similar substances. As electron transfer (ET)-based total antioxidant capacity (TAC) assays generally measure the reducing ability of antioxidant compounds, thiols and phenols cannot be differentiated since they are both responsive to the probe reagent. In this study, three of the most common TAC determination methods, namely cupric ion reducing antioxidant capacity (CUPRAC), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt/trolox equivalent antioxidant capacity (ABTS/TEAC), and ferric reducing antioxidant power (FRAP), were tested for the assay of phenolics in the presence of selected thiol and protein compounds. Although the FRAP method is almost non-responsive to thiol compounds individually, surprising overoxidations with large positive deviations from additivity were observed when using this method for (phenols + thiols) mixtures. Among the tested TAC methods, CUPRAC gave the most additive results for all studied (phenol + thiol) and (phenol + protein) mixtures with minimal relative error. As ABTS/TEAC and FRAP methods gave small and large deviations, respectively, from additivity of absorbances arising from these components in mixtures, mercury(II) compounds were added to stabilize the thiol components in the form of Hg(II)-thiol complexes so as to enable selective spectrophotometric determination of phenolic components. This error compensation was most efficient for the FRAP method in testing (thiols + phenols) mixtures.
منابع مشابه
Identification of phenolic antioxidants in Ipomoea mauritiana jacq. using spectrophotometric and mass spectroscopic studies
Objective: Ipomoea mauritiana is used in both Ayurveda and folk medicine systems. The tuberous roots are known to be diuretic, depurative, carminative, and anthelmintic. The objective of the current study was to identify phenolic antioxidants from I. mauritiana using spectrophotometric and LC-MS analysis. Materials and Methods: An activity-guided fractionation and purification process was used t...
متن کاملDetermination of Synthetic Phenolic Antioxidants in Biological Fluids Based on Air-assisted Liquid-liquid Microextraction Followed by Gas Chromatography-flame Ionization Detection
An air–assisted liquid–liquid microextraction method for the extraction and preconcentration of trace amounts of some synthetic phenolic antioxidants in biological fluids followed by their determination by gas chromatography–flame ionization detection has been reported. In this method the target analytes are extracted into a few microliters of carbon tetrachloride (extraction solvent) from an a...
متن کاملFast high performance liquid chromatography and ultraviolet-visible quantification of principal phenolic antioxidants in fresh rosemary.
An improved HPLC method is reported for the determination of rosemary's principal phenolic antioxidants, rosmarinic and carnosic acids, providing a fast and simultaneous determination for both of them by using a solid phase column. The analysis was performed with fresh methanolic extractions of Rosmarinus officinalis. To quantify the amount of antioxidants in a fast and reproducible way by mean...
متن کاملTitrimetric and Spectrophotometric Methods for the Determination of β-blockers in Pharmaceutical Dosage Form
Three new methods using titrimetric and spectrophotometry are described for the determination of Propranolol Hydrochloride (PPH) and Atenolol (AN) with potassium bromate as the oxidimetric reagent and acid dyes, Methyl orange and Indigo carmine. In direct titrimetric (method A), the drug is titrated directly with bromate in acid medium and in the presence of excess of bromide using methyl orang...
متن کاملIdentification, determination, and study of antioxidative activities of hesperetin and gallic acid in hydro-alcoholic extract from flowers of Eriobotrya japonica (Lindl.)
Objectives: Eriobotrya japonica belongs to the Rosaceae. Studies have shown that the flowers of this plant are rich in phenolic and flavonoid compounds. Accorrdingly, the evaluation of antioxidative effects of Eriobotrya japonica Flower Extract (EJFE) have been performed in vitro. Material and Methods: In this study, to investigate the influences of components of EJFE on its antioxidative activ...
متن کامل