Hypochlorite scavenging activity of hydroxycinnamic acids evaluated by a rapid microplate method based on the measurement of chloramines

Abstract

Scavengers of hypochlorite (XOCl) could have beneficial effects in diseases in which this oxidant plays a pathogenic role. It has been reported that ferulic acid and chlorogenic acid, the quinic ester of caffeic acid, are good hypochlorite scavengers, but a systematic evaluation of the naturally occurring hydroxycinnamic acids (HCAs), which these substances belong to, has not been performed yet. Thus, in this work we studied, by two different in-vitro methods, the antioxidant activity of five HCAs: p-coumaric acid, ferulic acid, sinapinic acid, caffeic acid and chlorogenic acid. The methods applied in this study were based on the oxidation of human serum albumin (HSA) by XOCl, a new microplate method based on the measurement of chloramines and a previously described carbonyl assay. Firstly, lysine-derived chloramines, in the presence or absence of the HCAs, were detected using 5-thio-2-nitrobenzoic acid (TNB), measuring the absorbance at 415 nm by a microplate reader. To remove excess XOCl, Trolox, a known XOCl scavenger, was added before TNB. Secondly, lysine-derived carbonyls, in the presence or absence of the HCAs, were detected by using 2,4-dinitrophenylhydrazine. Hydroxycinnamic acids appeared active (caffeic >/= sinapinic > chlorogenic congruent with ferulic > p-coumaric acid) by both methods, suggesting possible pharmacological applications for these compounds, which are present at high concentrations in the plant kingdom.

Antioxidant Properties of Hydroxycinnamic Acids: A Review of Structure- Activity Relationships

“…The authors postulated that the enhancement of activity is related to the electron-donation properties of the methoxy moiety that can stabilize the phenoxy radical formed in the reaction with free radicals. The superior activity of ferulic acid compared to para-coumaric acid has been observed also by other authors [47,124,125]. Addition of the second methoxy group (as in the structure of sinapic acid Fig.…”

“…Addition of the second methoxy group (as in the structure of sinapic acid Fig. 1) further increases the activity, as deducted from the comparison of sinapic acid with ferulic acid in hypochlorite scavenging [47] and DPPH scavenging assays [125,126]. Similarly, the results of our group and others have demonstrated that esters of sinapic acid are more active than esters of ferulic acid in �-carotene-linoleic acid system [127] and in DPPH assay [126].…”

“…Greater hypochlorite scavenging [47] and singlet oxygen quenching abilities [84] of caffeic acid (dihydroxy substi-tuted) over para-coumaric acid (monohydroxy substituted) have been previously reported. Also in ferrylmyoglobin-dependent LDL peroxidation assay the activity of HCAs is highly dependent on the number of hydroxy groups: ortho-dihydroxy derivatives (caffeic and chlorogenic acids) could act as efficient LDL peroxidation blocking agents when compared to para-coumaric acid [114].…”

“…HCAs have been shown to be phytochemicals with remarkable antioxidant outlines they are able; a) to increase the resistance of low density lipoprotein (LDL) to lipid peroxidation [56,79,80]; b) to protect proteins against oxida-tion [81]; c) to chelate transition metals that catalyze oxida-tive reactions [82]; d) to scavenge a variety of ROS [47,[83][84][85][86]; e) to inhibit enzymes that are involved in oxidative stress [48,87].…”

“…HCAs and their derivatives have a broad spectrum of biological activities including antitumoral [42][43][44][45], antimicrobial [46], antioxidant [47][48][49][50][51][52] and neuroprotective effects [53][54][55].…”