Effect of Low Temperature Cultivation on the Phytochemical Profile and Bioactivity of Arctic Plants: A Case of Dracocephalum palmatum

The influence of climatic factors, e.g., low temperature, on the phytochemical composition and bioactivity of the arctic plant Dracocephalum palmatum Steph. ax Willd. (palmate dragonhead), a traditional food and medical herb of Northern Siberia, was investigated. D. palmatum seedlings were grown in a greenhouse experiment at normal (20 °C, NT) and low (1 °C, LT) temperature levels and five groups of components that were lipophilic and hydrophilic in nature were characterized. The analyses indicated that D. palmatum under NT demonstrates high content of photosynthetic pigments, specific fatty acid (FA) profile with domination of saturated FA (53.3%) and the essential oil with trans-pinocamphone as a main component (37.9%). Phenolic compounds were identified using a combination of high performance liquid chromatography with diode array detection and electrospray ionization mass-spectrometric detection (HPLC-DAD-ESI-MS) techniques, as well as free carbohydrates and water soluble polysaccharides. For the first time, it was established that the cold acclimation of D. palmatum seedlings resulted in various changes in physiological and biochemical parameters such as membrane permeability, photosynthetic potential, membrane fluidity, leaf surface secretory function, reactive oxygen species-antioxidant balance, osmoregulator content and cell wall polymers. In brief, results showed that the adaptive strategy of D. palmatum under LT was realized on the accumulation of membrane or surface components with more fluid properties (unsaturated FA and essential oils), antioxidants (phenolic compounds and enzymes), osmoprotectants (free sugars) and cell wall components (polysaccharides). In addition, the occurrence of unusual flavonoids including two new isomeric malonyl esters of eriodictyol-7-O-glucoside was found in LT samples. Data thus obtained allow improving our understanding of ecophysiological mechanisms of cold adaptation of arctic plants.