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Free‐Radical‐Scavenging Effect of Carbazole Derivatives on DPPH and ABTS Radicals
Author(s) -
Tang YouZhi,
Liu ZaiQun
Publication year - 2007
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-007-1149-y
Subject(s) - chemistry , abts , dpph , trolox , phenoxazine , diphenylamine , organic chemistry , ascorbic acid , medicinal chemistry , acetic acid , gallic acid , photochemistry , nuclear chemistry , antioxidant , phenothiazine , food science , medicine , pharmacology
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′‐diphenyl‐1‐picrylhydrazyl (DPPH) and the 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate) radical cation (ABTS +· ). The Ar 2 NHs included phenoxazine (PozNH), phenothiazine (PtzNH), iminostilbene (IsbNH) and diphenylamine (DpaNH), and the TEAC of trolox, α‐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 +· . 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.