Antioxidant Properties of Plant Plastoquinone in Vivo and in Vitro

Plastoquinone (PQ) is a mobile electron carrier from photosystem II to the cytochrome b₆/f complex in the photosynthetic electron transport chain (PETC). In addition, PQ acts together with many other isoprenoids to perform the antioxidant function and to protect plant cells from reactive oxygen species (ROS). The review describes the PQ reactions with ROS, including singlet oxygen, superoxide anion radical, and hydrogen peroxide, in chloroplasts of higher plants. Data from many studies on the effect of various stress factors on PQ biosynthesis were analyzed to demonstrate that the PQ content increases in almost all stress conditions. An increase in PQ biosynthesis is therefore a factor that contributes to the plant viability by protecting the photosynthetic apparatus from oxidative degradation. A special section describes the methods to create plants with a higher PQ level and to assess their resistance to environmental factors. Applications of plant PQ as a protector of membrane structures from oxidation are discussed on the basis of its high antioxidant activity and the capability of diffusing in the lipid phase.