Quantitative profile of phenolic acids and antioxidant activity of wheat grain exposed to stress

Abstract

In the case of biotic and abiotic stresses, natural defence mechanisms are triggered in plants. The mechanisms are based mainly on enzymatic or non-enzymatic intracellular reactions. Changes in the quantitative profile of 12 phenolic acids, total bound phenolic acids, total free phenolic acids and antioxidant activity in grain of 23 winter wheat genotypes exposed to stress (artificial inoculation with spores of fungi from the genus Fusarium or chemical protection) were analysed. Concentrations of ergosterol confirm significantly higher levels of contamination with microscopic fungi in inoculated wheat samples in comparison to the control and chemically protected samples. The highest concentrations of bound phenolic acids were recorded in inoculated samples while the control and chemically protected samples did not differ significantly. Chromatographic analysis of contents of 12 bound phenolic acids showed that significant differences were found for contents of ferulic, synapic, t-cinnamic and 4-hydroxybenzoic acids in experimental variants. Stepwise discriminatory analysis based on the contents of selected bound phenolic acids antioxidant activity and free phenolic acids led to a complete separation of the investigated populations of the experimental groups. The statistical analysis confirmed that free phenolic acids are the most significant factors in resistance mechanisms as the first line of defence together with their antioxidant action, followed by the synergistic effect of exogenous bound phenolic acids: ferulic, synapic, t-cinnamic and 4-hydroxybenzoic acids.