Kinetic and Stoichiometry of the Reaction of Chlorogenic Acid and Its Alkyl Esters against the DPPH Radical

Abstract

The lipophilization of polar antioxidants such as phenolics is an efficient way to enhance their solubility in apolar media. Thus, in emulsified systems, lipophilized antioxidants are supposed to locate at the lipid/aqueous phase interface and to lead to a better protection of unsaturated lipids. Herein, the antiradical activity of chlorogenic acid (5-CQA) and its corresponding esters with seven fatty alcohols (from methanol to eicosanol) have been achieved using the well-known 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Hydrophobation was shown to significantly improve the antiradical activity of 5-CQA esters which reached a maximum for butyl- and octyl-chlorogenate. In addition, for both 5-CQA and its esters, it was demonstrated that the global mechanism of DPPH* stabilization proceeded likely by electron transfer (ET), while it appeared that the pathways of DPPH* stabilization were different between 5-CQA and its esters, as confirmed by the LC-MS characterization of reaction products. Finally, strong differences were found between the tested molecules allowing the proposal of different DPPH* stabilization pathways by electron transfer for 5-CQA and its esters.

Evaluation of reduction kinetics of 2,2-diphenyl-1-picrylhydrazyl radical by flavonoid glycoside Rutin in mixed solvent based micellar media

“…This step is typically followed by a much slower decrease in visible absorbance, featuring the residual H-donating ability of the antioxidant degradation products (slow step). It is worth mentioning here that only the fast stages of the reaction (100 s) were detailed in terms of kinetic analysis (Scheme 2), where it is commonly accepted that the stabilization of DPPH radicals results from the transfer of the most labile H atoms of the antioxidants (-OHs) [29]. The rate constant (k) of the reaction was determined in all the systems at 25 • C by monitoring the decay of DPPH absorbance at 515 nm.…”

“…The rate constant (k) of the reaction was determined in all the systems at 25 • C by monitoring the decay of DPPH absorbance at 515 nm. The rate of DPPH reduction under these conditions can be written as follows [26,29]:…”

Does hydrophobicity always enhance antioxidant drugs? A cut-off effect of the chain length of functionalized chlorogenate esters on ROS-overexpressing fibroblasts

“…Recently, we have shown that chlorogenic acid (5‐caffeoylquinic acid, Figure 1), exhibiting antioxidant [10] and antiradical [11] properties in test tube‐based assays, can be lipophilized by various fatty alcohols in a two‐step lipase‐catalysed transesterification strategy [12] . This reaction leads to a homologous series of alkyl chlorogenate esters (from methyl to hexadecyl, Figure 1), which constitutes an interesting phenolic model to study the impact of the hydrophobicity on the antioxidant capacity in biological samples.…”

Antioxidant Activity of a Oryzanols Concentrate by Differential Scanning Calorimetry

“…This antioxidant activity is attributed to the presence of the ferulate group in its chemical structure. It should be considered that the presence of different groups esterified in a phenolic antioxidant may play an attenuating role or antioxidant capacity enhancement (López, Laguerre, Lecomte, Figueroa, Barea, Weiss, Decker, & Villeneuve, 2009). Therefore, it is important to study and compare its antioxidant power with that of other antioxidants in different types of oils.…”