Stress-protective effect of phenylpropanoid complex on potato plants in vitro

In order to identify factors governing the maintenance of intracellular redox homeostasis, we investigated the effect of phenylpropanoid complex (PPC) isolated from the root extract of Golden root (Rhodiola rosea L.) on the plants of potato (Solanum tuberosum L.) in vitro. It was found that plant treatment with 100 mu M PPC brought about a 23% decrease in peroxidase activity in the cells of potato plants and induced a reversible increase in the level of lipid peroxidation (POL) under oxidative stress caused by paraquat. In the presence of NADH known as an oxidase substrate of peroxidases (PO), a decrease in peroxidase activity was associated with switching peroxidase over to oxidase function. This effect was accompanied by a rise in the superoxide dismutase activity by 34% and identical POL elevation. After plant pretreatment with NADPH-oxidase inhibitor diphenylene iodinum, the stimulation of these processes upon the exposure to PPC decreased by 14 and 24%, respectively. This may point to the participation of a PO/NADPH-oxidase tandem in ROS generation. Along with a decrease in peroxidase function of PO, we also observed an opposite effect: in 3 h after the exposure to PPC, its activity rose, which depended on the ability of PPC to switch peroxidase from oxidative to reductive function and back. It was found that the observed effects of PPC comprise not only the respective modulation of antioxidant enzyme activity but also direct ROS quenching. The latter effect of PPC, detected by the rate of a decrease in the level of superoxide anion considerably exceeded the effect of individual antioxidants (salidroside and ascorbic acid), whose inhibitory activity was 5 times lower than the activity of PPC.