The Effect of Dihydroquercetin on Programmed Cell Death and Formation of Reactive Oxygen Species in the Epidermis of Pea Leaves

Dihydroquercetin (DHQ, taxifolin) is a plant flavonoid that exhibits antioxidant and cytoprotective properties in animal and human cells. Its effect on programmed cell death (PCD), respiration, photosynthesis, and the formation of reactive oxygen species (ROS) in plant cells has been shown. At concentrations of 0.1–3 mM, DHQ suppressed KCN-induced PCD in guard cells of pea leaf epidermis in the light or in the dark, which was determined by the destruction of cell nuclei. In pea leaf cuttings, DHQ had no effect on respiration, as measured by O₂ consumption in the dark. DHQ did not affect photosynthetic O₂ evolution by leaf cuttings with p-benzoquinone and ferricyanide as electron acceptors nor on the consumption of oxygen as a result of the oxidation of ascorbate and N,N,N′,N′-tetramethyl-p-phenylenediamine and the reduction of methyl viologen in the light in PS I. DHQ inhibited menadione-induced ROS formation in pea leaf epidermis, which was detected by fluorescence 2′,7′-dichlorofluorescein. DHQ itself had no effect on H₂O₂ in solution, but it utilized hydrogen peroxide in combination with peroxidase. The antioxidant effect of DHQ and protection of plant cells from death may be due to its suitability as a peroxidase substrate.