Determination of Total Antioxidant Capacity of Lipophilic and Hydrophilic Antioxidants In the Same Solution by Using Ferric-Ferricyanide Assay

The purpose of this work is to develop a simple, low-cost, and diversely applicable antioxidant capacity assay, the ferric-ferricyanide method based on Prussian blue formation, for both lipophilic and hydrophilic antioxidants in food matrices. The trolox equivalent antioxidant capacities of various antioxidant compounds were calculated with respect to the ferric-ferricyanide, FRAP, and modified CUPRAC methods. The linear calibration curves of the ferric-ferricyanide assay for lipophilic antioxidants (as absorbance vs. concentration) in 1:9 (v/v) H2O-acetone mixture solution with and without 2% M beta CD were comparatively drawn. Simultaneous determination of lipophilic and hydrophilic antioxidants could be achieved without using M beta CD. Testing of synthetic mixtures of lipophilic and hydrophilic antioxidants in 1:9 (v/v) H2O-acetone medium with the proposed method yielded the theoretically expected antioxidant capacities, considering the additivity of absorbances of constituents obeying Beer's law. The proposed assay is simple, versatile, and cost-effective; its reagents are cheap and stable, and can be performed using a simple colorimeter

Solid-Phase Extraction Spectrophotometric Determination of Total Antioxidant Capacity in Antioxidant-poor Samples by Using the Ferric-Ferrozine Method

Ferrozine (FZ) preferentially stabilizes Fe(II) over Fe(III) to raise the ferric reduction potential and oxidize antioxidants. The advantages of the ferric-ferrozine method over other iron-based total antioxidant capacity assays were: (i) higher molar absorptivity and enhanced sensitivity, (ii) lower interference from foreign ions, (iii) wide pH tolerance (iv) additivity of the absorbances for mixtures. Solid-phase extraction (SPE) could be combined with spectrophotometry, because the magenta-colored anionic Fe(II)-FZ complex was quantitatively sorbed on Sephadex QAE A-25 resin. The sensitivity enhancement using the resin enabled us to conduct total antioxidant capacity (TAC) measurements of antioxidant-poor samples. The apparent molar absorptivity, linear concentration range and trolox equivalent antioxidant capacities (TEAC) of certain antioxidants were found. The calibration curves (lines) of trolox, rutin, and rosmarinic acid individually and in herbal infusions by using the method of standard additions-were parallel, confirming that the added antioxidants did not interact with herbal constituents to cause chemical deviations from Beer's law

Folin-Ciocalteu spectrophotometric assay of ascorbic acid in pharmaceutical tablets and orange juice with pH adjustment and pre-extraction of lanthanum(III)-flavonoid complexes

BACKGROUND: This study proposes modifications to the conventional Folin-Ciocalteu (FC) spectrophotometric method for individually determining ascorbic acid (AA) in complex matrices in the presence of other phenolics and potential interferents. The conventional FC assay in the aqueous phase, which normally measures total water-soluble phenolics and other antioxidants, has recently been modified by incorporating isobutanol (iso-BuOH) in the solvent mixture for the simultaneous determination of lipophilic and hydrophilic antioxidants in foods