Plant Phenolics Affect Oxidation of Tryptophan

Abstract

The effect of berry phenolics such as anthocyanins, ellagitannins, and proanthocyanidins from raspberry (Rubus idaeus), black currant (Ribes nigrum), and cranberry (Vaccinium oxycoccus) and byproducts of deoiling processes rich in phenolics such as rapeseed (Brassica rapa L.), camelina (Camelina sativa), and soy (Glycine max L.) as well as scots pine bark (Pinus sylvestris) was investigated in an H2O2-oxidized tryptophan (Trp) solution. The oxidation of Trp was analyzed with high-performance liquid chromatography using both fluorescence and diode array detection of Trp and its oxidation products. Mechanisms of antioxidative action of the phenolic compounds toward the oxidation of Trp were different as the pattern of Trp oxidation products varied with different phenolic compounds. The antioxidant protection toward oxidation of Trp was best provided with pine bark phenolics, black currant anthocyanins, and camelina meal phenolics as well as cranberry proanthocyanidins.

Analysis of tryptophan oxidation by fluorescence spectroscopy: Effect of metal-catalyzed oxidation and selected phenolic compounds

“…1) (Procházková et al, 2011). Similar findings were observed by Salminen and Heinonen (2008) during the oxidation of TRYP by H 2 O 2 , as catechin and quercetin provided a clear protection against TRYP oxidation. On the contrary, pro-oxidant activity of catechol structures have been related to the formation of quinone-type oxidation products (Rietjens et al, 2002).…”

“…According to the present results, the extent of TRYP oxidation largely depends on the oxidative conditions. Consistently, Salminen and Heinonen (2008) observed different degradation patterns and rates of TRYP oxidation depending on the incubation time, the amount of oxidant, pH and temperature during the in vitro oxidation of TRYP. Both transition metals studied are naturally present in a large variety of foods in which they are known to exert pro-oxidant actions.…”

“…Moreover, chlorogenic acid exhibited a clear protective effect against the formation of carbonyls during oxidation on myofibrillar proteins by Cu 2+ /H 2 O 2 , but exerted pro-oxidant actions in similar systems with added Fe 3+ and myoglobin (Estévez et Flavones with a monohydroxy configuration in the B-ring Heinonen, 2010). Likewise, chlorogenic acid showed, in previous studies, a significant antioxidant effect toward the oxidation of TRYP by H 2 O 2 (Salminen & Heinonen, 2008). The lack of consistency between the different findings would be explained in terms of the oxidation target molecules (amino acids vs complex proteins), oxidation conditions (metal catalyst, presence or absence of H 2 O 2 ), and protein oxidation measurements (hexanal, fluorescent Schiff bases, specific protein carbonyls, TRYP fluorescence).…”

“…However, all these methods require complex and time-consuming sample-preparation procedures, qualified personnel and costly equipments. Moreover, only about 20% of the TRYP loss could be elucidated by the quantification of TRYP degradation compounds (Salminen & Heinonen, 2008;Simat & Steinhart, 1998). Therefore, the development of novel and simpler techniques to precisely assess TRYP oxidation is of great interest.…”

Light emission from tryptophan oxidation by hypobromous acid

“…Using both oxidants, tryptophan was partially consumed and generated several products, which are typically obtained when this amino acid is oxidized using oxidants such as hydrogen peroxide (21) and chlorine dioxide (22) and electrochemical oxidation (23). Using both oxidants, tryptophan was partially consumed and generated several products, which are typically obtained when this amino acid is oxidized using oxidants such as hydrogen peroxide (21) and chlorine dioxide (22) and electrochemical oxidation (23).…”