Metabolomics-Based Comprehensive Exploration of the Bioactive Compound in Saposhnikovia divaricata (Turcz.) Schischk. in Response to Exogenous Nitrogen.

Saposhnikovia divaricata (Turcz.) Schischk. (S. divaricata), a traditional Chinese medicine, is renowned for its dried roots rich in phenolic compounds, which exhibit significant medicinal values in anti-inflammatory, analgesic, and other therapeutic fields. Cultivating medicinal plants has been validated as an effective strategy to enhance the supply of phenolic-rich raw materials. However, the efficient fertilization strategy of nitrogen-a key nutrient-and its regulatory mechanisms on plant growth and phenolic metabolism in S. divaricata remain unclear. This study aimed to explore nitrogen's effects on S. divaricata growth and phenolic accumulation. Field experiments used four nitrogen treatments: no nitrogen fertilization (CK), low nitrogen fertilization (9 g/m²), medium nitrogen fertilization (18 g/m²), and high nitrogen fertilization (27 g/m²). Growth indices and phenolic metabolites were analyzed via UPLC-MS and multivariate statistics. The results showed that the medium nitrogen treatment (18 g/m²) significantly promoted the growth of S. divaricata, with plant height and single-plant biomass reaching 26 ± 0.3 cm and 19.04 ± 0.96 g, respectively, and optimal root development (root length 14.7 ± 0.2 cm). Additionally, nitrogen application significantly promoted the synthesis of phenolic compounds and enhanced the tolerance of S. divaricata to nitrogen stress, which is conducive to safeguarding and elevating its medicinal value. For specific bioactive substances, the contents of prim-o-glucosyl-cimifugin, 4'-o-β-glucosyl-5-o-methylvisamminol, cimifugin, and sec-o-glucosylhamaudol in S. divaricata under medium nitrogen concentration were notably higher than those in the no-nitrogen fertilization group. This study confirms that medium nitrogen levels can synergistically enhance the growth and accumulation of medicinal active components in S. divaricata, providing a theoretical basis for the precise application of nitrogen fertilizers and quality regulation in medicinal plant cultivation.