Hydroxyl radical production by ascorbate and hydrogen peroxide

Abstract

Ascorbate (AH') and certain other biological reductants have long been known to produce the cytotoxic hydroxyl radical ('OH) when oxidized by hydrogen peroxide (H202) in the presence of copper or iron catalysts. The present study documents the in vitro production of the "OH solely from the oxidation of AH-by H202, independent of mediation by transition metals. Hydroxyl radical generation resulting from the AH'/H202 system was quantitatively documented by the specific radical-mediated hydroxylation of salicylic acid, a reaction that was readily assayed with HPLC coupled with electrochemical detection. Two ascorbate-copper complexes (e.g., AH-/Cu2+-EDTA/H202 and AH'/Cu2+-EDTA) and a copper/H202 system also generated 'OH, but less effectively than the AH'/H202 system. The ability of AH-and H202 to generate cytotoxic "OH documents a reaction mechanism that may account for cytotoxic activity in some cellular environments where metal catalysts are lacking.

Application of ascorbic acid to enhance trichloroethene degradation by Fe(III)-activated calcium peroxide

“…4). It was believed that AA transformed to DHAA and also partly oxidized to other products such as oxalic acid and L-threonic acid [39]. AA and its products can be oxidized by HO• due to its scavenging property and also by other organic species such as CH 3 O 2 • which reacts with AA at a rate constant of 1.7×10 6 M −1 s −1 [40].…”

Antioxidant Capacity of “Mexican Arnica”Heterotheca inuloidesCass Natural Products and Some Derivatives: Their Anti-Inflammatory Evaluation and Effect onC. elegansLife Span

“…In biological systems H 2 O 2 produces hydroxyl ions and hydroxyl radicals by reacting with Fe 2+ and Cu 2+ ions and they have been related to the initiation of many toxic effects [ 41 ]. It is therefore biologically advantageous for cells to control the accumulation of H 2 O 2 .…”

An Original HPLC Method with Coulometric Detection to Monitor Hydroxyl Radical Generation via Fenton Chemistry

“…At first, the Fenton’s reaction was triggered in order to obtain •OH generation. A sensitive and specific salicylate (2-hydroxybenzoic acid) hydroxylation assay was used [27] to monitor •OH production in conjunction with high-performance liquid chromatography with electrochemical detection (HPLC-ED), in particular by means of a coulometric detector. The products of •OH-mediated salicylate hydroxylation, which include 2,3- and 2,5-dihydroxybenzoic acid (2,3-DHBA and 2,5-DHBA) and catechol (Figure 1) [28], were detected and quantitated.…”

“…Some published papers describe assays for the detection of •OH formation via Fenton’s reaction [20,27] and •OH production evaluation through HPLC-ED determination of hydroxylated salicylic acid [27,29,30,31,32] or tyrosine [33]. The method that uses tyrosine derivatives was, however, not characterized in detail (method validation results are mostly missing; method details are insufficient to allow replication) [33].…”