Free‐Radical‐Scavenging Effect of Carbazole Derivatives on DPPH and ABTS Radicals

Abstract

The major objective was to measure the trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) equivalent antioxidant capacity (TEAC) of carbazole derivatives (Ar 2 NHs) by means of scavenging 2,2 0 -diphenyl-1-picrylhydrazyl (DPPH) and the 2,2 0 -azinobis(3-ethylbenzothiazoline-6-sulfonate) radical cation (ABTS +Á ). The Ar 2 NHs included phenoxazine (PozNH), phenothiazine (PtzNH), iminostilbene (IsbNH) and diphenylamine (DpaNH), and the TEAC of trolox, a-tocopherol (TocH), L-ascorbic acid (VC) and L-ascorbyl-6-laurate (VC-12) were measured as well. The TEAC results revealed that the ability to scavenge DPPH (PozNH [ IsbNH *PtzNH * TroH *TocH *VC *VC12), differed from the ability to scavenge ABTS + (PtzNH [ IsbNH [ PozNH [ DpaNH * TroH *TocH *VC *VC12). CazNH did not react with DPPH and ABTS +Á . Furthermore, the addition of acetic acid accelerated the reaction rate of Ar 2 NH to scavenge DPPH, suggesting that a sequential proton loss electron transfer (SPLET) mechanism occurred with amine-type antioxidants during the trapping of DPPH. In contrast, the addition of acetic acid or pyridine reduced the reaction rate of Ar 2 NH to scavenge ABTS +. , suggesting that the hydrogen atom transfer (HAT) mechanism is the basis for the reaction that is occurring.

Scavenging capacities of some thiazolyl thiazolidine‐2,4‐dione compounds on superoxide radical, hydroxyl radical, and DPPH radical

“…However, the effect was relatively lower compared with that ascorbic acid and Tiron at the concentrations similar to that used during the compound evaluation. The DPPH radical is a compound that has been widely used to test the free radical scavenging ability of various substances (35)(36)(37)(38)(39). The radical decreases in the presence of proton radical scavengers (40).…”

“…• is a result of the competition of two mechanisms, hydrogen transfer and sequential proton loss electron transfer (36). The last mechanism suggest that partial ionization of the antioxidant can enhance proton transfer to DPPH • .…”

Diclofenac acid: a free‐radical‐scavenger to protect DNA against radical‐induced oxidation

“…AAPH was dissolved in phosphate-buffered solution (PBS: 8.1 mM Na 2 HPO 4 , 1.9 mM NaH 2 PO 4 , 10 mM EDTA, pH 7.4). The other two radical-related solutions were prepared as described [Tang and Liu, 2007a]. Briefly, DPPH was dissolved in ethanol ($100 mM) to give an absorbance $1.00 at 517 nm (Abs ref ).…”

“…The reactions between DaH (or its sodium salt) and ABTS þ: , DPPH were carried out as previously described [Tang and Liu, 2007a] [Tang and Liu, 2007a].…”

Schiff’s base derivatives of murrayanine demonstrated enhanced anti-oxidant activity than its parent moiety

“…The mechanism(s) for free radical scavenging is not known exactly; however probable mechanism(s) involve the interaction between the hydroxyl functional group of the carbazole derivatives and the DPPH; where sequential proton loss electron transfer (SPLET) is an indication of the ability of the antioxidant to scavenge free radicals. 25 The study highlighted that the structure has a key influence on biological activity. The structureactivity relationship may be established where it was observed that carbazole scaffold remained a foremost need for exhibiting anti-oxidant activity.…”