Caffeic acid decomposition products: Antioxidants or pro-oxidants?

Abstract

a b s t r a c tThe potential of phenol antioxidants to suffer decomposition reactions leading to the formation of products exerting pro-oxidant activity was studied. A hydroalcoholic solution containing caffeic acid was assessed for antioxidant and pro-oxidant activity during heating at 90°C to simulate the heat maintenance of the coffee brews in thermos. Decomposition products were also evaluated by HPLC analysis. In the early steps of caffeic acid decomposition, a decrease in antioxidant capacity was detected, associated to a significant increase in pro-oxidant activity because the development of pro-oxidant compounds. On further heating, an increase in antioxidant activity associated to a decrease in pro-oxidant molecules previously formed and the formation of polymers with higher antioxidant activity was observed. A mechanistic route of caffeic acid decomposition under thermal conditions according to the HPLC analysis was proposed. This study clearly showed that caffeic acid, a well known antioxidant, may also act as pro-oxidant due to thermal decomposition.

Stability of hydroxycinnamic acids and caffeine from green coffee extracts after heating in food model systems

“…Taking into account the relation between hydroxycinnamic acids degradation and radical scavenging capacity only among the systems with a single substance and GCE, it can be concluded that a decrease in the antioxidant activity along with polyphenols degradation was observed. This observation is in turn consistent with previous reports relating to polyphenols degradation, which showed a reduced ability to scavenge radicals by polyphenols thermal degradation products when compared to initial polyphenols [37]. Heating of GCE components with sunflower oil probably resulted in forming ingredients of high antioxidant activity.…”

“…Heating of chlorogenic acid with inert material did not influence its antioxidant activity, which points out that the products of thermal degradation of chlorogenic acid also have a high antioxidant activity. Research on this topic was conducted by Andueza et al [37], who demonstrated that among the products of caffeic acid oxidation are ethylcatechol, vinylcatechol, phenylindanes, and quinones, which in the later stage of oxidation form polymers with high antioxidant activity. Regarding the addition of iron ions, a deterioration of antioxidative properties was observed, coming from the reaction of hydroxycinnamic acids with iron.…”

Contribution of volatile compounds to the antioxidant capacity of coffee

“…When coffee brew preparation was studied, coffee pressure-brewing procedures, such as espresso and mocha, extracted more volatiles and showed higher antioxidant capacity than plunger and filter procedures, but no significant correlations between volatiles and antioxidant activity were found (Lopez-Galilea, de Peña, & Cid, 2007). Despite the different approaches in the reported studies, the results might not be considered as contradictory if it is taken into account that some compounds proposed as antioxidants may act as pro-oxidants at different doses (Andueza, Manzocco, de Peña, Cid & Nicoli, 2009;Halliwell, 2008) and that most of the works which study the antioxidant activity of volatiles have been carried out using standard compounds at concentration levels higher than those present in coffee. Thus, these results cannot be directly transferred to the knowledge of the contribution of volatiles to the antioxidant capacity of coffee.…”

Green and roasted coffee extracts as antioxidants in βTC3 cells with induced oxidative stress and lipid accumulation inhibitors in 3T3L1 cells, and their bioactivity in rats fed high fat diet

“…The extracts were evaluated in vitro in terms of scavenging capacity, influence on lipids accumulation in 3T3L1 adipocytes, cytoprotective potential decreasing oxidative stress induced by cellular pro-oxidants in βTC3 cells, and in vivo by selected physiological indices in rats fed diets supplemented with the extracts. Roasted coffee extracts, in particular hydrophilic fraction containing monochlorogenic acids and Maillard reaction products, showed the highest scavenging capacity and contributed to the products of their changes exhibit many bioactivities [15]. There is also no available research if the mixture of all coffee CHAs or fractions like more hydrophilic monoesters or more hydrophobic diesters are more bioactive.…”