Measurement of antioxidant activity with trifluoperazine dihydrochloride radical cation

Abstract

A novel, rapid and cost-effective trifluoperazine dihydrochloride (TFPH) decolorization assay is described for the screening of antioxidant activity. A chromogenic reaction between TFPH and potassium persulfate at low pH produces an orange-red radical cation with maximum absorption at 502 nm in its first-order derivative spectrum. TFPH was dissolved in distilled water to give a 100 mM solution. The TFPH radical cation solution was made by reacting 0.5 mL of the solution with K 2 S 2 O 8 (final concentration: 0.1 mM) and diluting to 100 mL with 4 M H 2 SO 4 solution. A linear inhibition of color production was observed with linearly increasing amounts of antioxidants, with correlation coefficients (R 2 ) ranging from 0.999 to 0.983. The antioxidant capacity of standard solutions of an antioxidant was evaluated by comparing with the inhibition curve using Trolox as the standard. Comparison of antioxidant capacity determined with this newly developed TFPH assay and with the well-known 2,2'-azinobis-[3-ethylbenzthiazoline-6-sulfonic acid] (ABTS)-persulfate decolorization assay indicated the efficacy and sensitivity of the procedure. The proposed assay is less expensive (costs about US$4 per 100 assays) and requires only 20 min for preparation of radical cation solution in comparison with ABTS assay, in which almost 12-16 h are required for preparation of a stable ABTS radical cation solution. The present assay has the advantage over ABTS assay that it can be used to measure the antioxidant activity of the samples, which are naturally found at a pH as low as 1, because the radical cation itself has been stabilized at low pH.

Variability in the Qualitative and Quantitative Composition and Content of Phenolic Compounds in the Fruit of Introduced American Cranberry (Vaccinium macrocarpon Aiton)

“…TFPH ⋅+ Assay . 3 mL of TFPH ⋅+ solution was mixed with 10 µL of extracts, and absorbance was measured at λ = 502 nm [ 57 ]. A calibration curve (𝑦 = 0.0000371𝑥 + 0.1471727; R 2 = 0.9959) was prepared using standard Trolox solutions of 2000 to 16,000 µmol/L concentration.…”

Exploitation of amaranth oil fractions enriched in squalene for dual delivery of hydrophilic and lipophilic actives

“…A 0 is the absorbance of the blank (unscavenged radical cation solution), while A s is the absorbance after the addition of the antioxidant sample (NLCs or Trolox) (Asghar and Khan, 2008).…”

In vitro antioxidant and radical-scavenging capacities ofCitrullus colocynthes(L) andArtemisia absinthiumextracts using promethazine hydrochloride radical cation and contemporary assays

“…Phenothiazine radical cations have an oxidation potential similar to that of hydroxyl radical, but are in vitro much more stable which led to them being used for measuring the antioxidant activity of biological and abiological samples (Asghar and Khan, 2008; Re et al, 1999). The oxidation reaction of the PMZH is represented by Figure 1.…”

“…Decolorization assays which are based upon in vitro generation of a colored species and its subsequent decolorization on reaction with antioxidant samples are frequently used for the evaluation of total antioxidant activity due to their simplicity, operational easiness and economic aspects (Cao et al, 1995; Ghiselli et al, 1995; Lonnrot et al, 1996; Miller et al, 1993, 1996; Rice-Evans and Miller, 1985, 1994, 1996; Rice-Evans et al, 1996; Salah et al, 1995; Wang et al, 1996; Wayner et al, 1985; Whitehead et al, 1995). In continuation of a systematic study for the development of novel decolorization assays based upon radical cations of phenothiazines and para -substituted aromatic amines, (Asghar and Khan, 2008; Asghar et al, 2007; Asghar et al, 2008; Khan et al, 2008), we have developed a novel antioxidant assays using radical cation of promethazine hydrochloride (PMZH). PMZH has been used as an antipsychotic drug, but its application for themeasurement of antioxidant activity of herbal extracts and pure antioxidants has never been exploited.…”