Pyrogallol aggravates arsenic toxicity in Triticum aestivum L. through oxidative stress and mineral imbalance

Pyrogallol (PG), a plant-derived phenolic compound, exhibits dual redox behaviour as either an antioxidant or pro-oxidant depending on cellular context; however, its interaction with metal and metalloid stress remains poorly understood. This study investigated whether exogenous PG amplifies arsenic-induced oxidative stress and disrupts mineral balance in detached shoot tissues of fifteen-day-old wheat (Triticum aestivum L.).

Detached wheat shoots were exposed to PG (5 mM), arsenic (As; 100 µM), or their combination under acute controlled conditions for 18 h. Oxidative stress markers (O₂^•-, H₂O₂, TBARS), antioxidant enzyme activities (SOD, CAT, APX), proline content, mineral composition (macro- and micro-elements by ICP-MS), and elemental composition (CHNS) were quantified. UV-Vis spectrophotometric titration and in silico molecular docking were used to assess potential PG-As⁵⁺ and PG-APX interactions, respectively. Two-way ANOVA,pearson correlation, and principal component analysis were performed to evaluate PG-As⁵⁺ interaction effects.

Combined PG + As treatment increased tissue As accumulation by 21% relative to As alone and markedly intensified oxidative stress, as evidenced by elevated lipid peroxidation and hydrogen peroxide levels. Antioxidant enzyme activities (SOD, CAT, and APX) were substantially reduced, and proline accumulation was not associated with attenuation of oxidative damage. Elemental analysis revealed significant disruptions in mineral composition alongside a decreased C: N ratio, indicative of impaired carbon-nitrogen metabolism. Two-way ANOVA confirmed a significant PG-As⁵⁺ interaction effect for 16 of 19 measured parameters, providing quantitative support for interaction rather than additive effects.

These findings suggest that PG may act as a redox-active pro-oxidant under combined stress, contributing to suppression of antioxidant defenses and disruption of mineral balance in detached wheat shoot tissues, with implications for future investigations into phenolic-metal/metalloid stress responses in cereals.