Phenols and antioxidative status of Raphanus sativus grown in copper excess

Abstract

Raphanus sativus L. cv. Rimbo was grown for 10 days after emergence in hydroponic culture containing 0.12 (control), 5, 10 and 15 micro M copper. The seeds were germinated in the presence of the copper solution. The Cu contents increased with the treatment in both shoots and roots, maintaining in the roots a value eight- to ten-fold higher than in the shoots. With the treatment both shoots and roots underwent growth inhibition and an increase in the percentage of dry weight. Membrane damage and lipid peroxidation increased and glutathione was oxidized as the copper concentration increased, indicating an acceleration of oxidative processes. Control shoots had high contents of reduced glutathione and low contents of phytochelatin-SH whereas roots showed an opposite pattern, suggesting an utilization of reduced glutathione for phytochelatin synthesis. In both parts phytochelatin-SH content reached the maximum at 5 micro M copper and then decreased, reaching at 15 micro M copper the control value in the roots and a value five-fold higher than the control value in the shoots. The main phenolic acids represented in R. sativus were chlorogenic, vanillic, caffeic, siringic, p-coumaric and ferulic acids whereas the least represented were gallic, protocatechuic and p-hydroxybenzoic acids. The phenolic acids as well as the total and reduced ascorbate contents increased with the intensification of copper treatment. Notwithstanding these changes, total ascorbate remained 35% higher in the shoots than in the roots. The reduced ascorbate was thus able to replenish reducing equivalents to phenoxyl radicals thus explaining the increase in the phenolic compounds.

RETRACTED ARTICLE: Antioxidants and ROS scavenging ability in ten Darjeeling tea clones may serve as markers for selection of potentially adapted clones against abiotic stress

“…Soluble, apoplastic PRXs can scavenge H 2 O 2 cooperating with phenolics (Takahama and Oniki 2000). Earlier works pointed out that the first step of antioxidant action is catalyzed by peroxidases where Phytophenolics can be regenerated from phenoxyl radicals by nonenzymatic reaction with ascorbate (reaction 2) inhibiting the formation of degraded products (Yamasaki et al 1997;Sekihama et al 2002;Sgherri et al 2003).…”

“…The commonly known ROS are superoxide radical (•O 2 − ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radical (•OH) originating from one, two or three electron transfers to di-oxygen (O 2 ). Plants develop several enzyme and antioxidative systems as a defensive force against excess ROS, which can slow down or scavenge or disrupt the oxidative chain reactions (Sgherri et al 2003).It was well established that nonenzymatic scavengers are essential in the protection of cellular components from most ROS, but they cannot cope with reducing radicals such as superoxide or metastable hydroperoxides (Chaudiere and Ferrari-Iliou 1999). Grudarzi and Pakniyal (2009) opined that the plants defend against ROS by inducing the activities of certain antioxidative enzymes like catalase, peroxidase, glutathione reductase and superoxide dismutase.…”

Physiological responses of Matricaria chamomilla to cadmium and copper excess

“…Cd also stimulated GPX in leaves and roots when tested at high concentrations, suggesting the possibility of Cdinduced oxidative stress. Since phenolics are known to participate in ROS scavenging via peroxidases (Sgherri et al, 2003), with respect to considerably accumulation of soluble phenolics in this study, this pathways seems to be probable. Our results contrast, however, with data recorded for example in Pisum sativum roots treated with 100 lM Cd and Cu for 4 days showing similar GPX activity (Chaoui et al, 2004).…”

“…In plants, tissue damage occurs when the capacity of antioxidative systems becomes lower than the amount of ROS generated (Sgherri et al, 2003). To minimize functional and structural damages, plants have developed different mechanisms enabling them to counteract negative effects caused by metals abundance in their tissue.…”

“…Cooperation of phenolic metabolites with antioxidative enzymes in ROS scavenging, e.g. with peroxidases, is well established (Sgherri et al, 2003). Moreover, phenolics can chelate metals (Vasconcelos et al, 1999).…”