Title : Different NO3- /NH4+ ratios omproved caffeic acid derivatives and alkylamides compounds in Echinacea purpurea as affected by salt stress
Abstract:
The contamination of the environment with nitrate (NO3-) and ammonium (NH4+) has become a significant concern addressed by researchers worldwide. Particularly, the impact of NO3- and NH4+ contamination on the phytochemical composition of medicinal plants, especially in saline conditions, remains a pressing question. In this study, we aimed to investigate this issue by cultivating Echinacea purpurea in hydroponic systems under different NO3-/NH4+ molar ratios (90:10, 80:20, and 70:30) and varying NaCl salinity levels (15, 30, and 60 mM). Using UPLC, LC-HRMS, and HPLC techniques, we analyzed various alkylamides and caffeic acid derivatives. Additionally, we assessed nitrate reductase (NR) activity, phenylalanine ammonia-lyase (PAL) enzyme activity, and adenosine triphosphate (ATP) levels following standard protocols. Exposure of Echinacea purpurea roots to a 90:10 NO3-/NH4+ molar ratio in the presence of 30 mM NaCl resulted in a notable increase in chicoric acid (up to 20.33 mg g-1 dry weight), caftaric acid (up to 8.51 mg g-1 dry weight), cynarin (up to 2.32 mg g-1 dry weight), echinacoside (up to 1.60 mg g-1 dry weight), and chlorogenic acid (up to 1.43 mg g-1 dry weight) content. The most abundant alkylamide, Dodeca-2E, 4E, 8Z-10 (E/Z)-tetraenoic acid isobutylamide, constituted 57.42% of the total dry weight at the 90:10 NO3-/NH4+ molar ratio in the presence of 30 mM NaCl. However, increasing salinity levels from 30 mM to 60 mM NaCl led to a significant decrease in phytochemical compounds by inhibiting NR and PAL activities. Furthermore, ATP levels were markedly reduced at the 60 mM NaCl level. Our findings indicate that increasing the NO3-/NH4+ molar ratio within the range of 70:30 to 90:10 at 30 mM NaCl could enhance phytochemical compounds. These results contribute valuable insights into improving phytochemical compounds in plants under NO3- and NH4+-contaminated environments and offer new perspectives on phytoremediation processes.
Key Words: Environmental pollution; Medicinal plant; NO3- toxicity; Nitrate reductase; Phytochemical compounds
