Variations in Flavonoid Metabolites Among Forsythia suspensa Populations in Response to Environmental Heterogeneity

Forsythia suspensa (Thunb.) Vahl, a pharmacopoeial medicinal plant, is valued for its therapeutic efficacy in heat-clearing detoxification, dispelling wind-heat, and promoting blood circulation to resolve stasis. Flavonoids, ubiquitous secondary metabolites in F. suspensa, are critically linked to pharmacological activities and exhibit diverse biological functions. To elucidate the chemotypic divergence and ecological drivers of its bioactive compounds, we conducted flavonoid metabolomic profiling across ten wild populations F. suspensa using UPLC-MS/MS. Results revealed significant inter-population variation in all twenty-nine flavonoid metabolites analyzed. Notably, Notably, Cinchonain Ic was significantly enriched in the JX population, Flavanomarein in the LT population, and Desmethylxanthohumol in the HX population. Association analysis with environmental variables further indicated that Sulfuretin, Apigenin-5-O-glucoside, and Flavanomarein were positively correlated with multiple precipitation-related variables (bio12-Annual Precipitation, bio14-Precipitation of Driest Month, bio17-Precipitation of Driest Month, and bio19-Precipitation of Coldest Quarter), whereas Vicenin 2 was negatively correlated with bio12, bio17, and bio19. Homoplantaginin showed a positive correlation with bio4 (Temperature Seasonality) and bio7 (Temperature Annual Range). Loureirin B was positively correlated with elevation but negatively correlated with high-temperature variables (bio5-Max Temperature of Warmest Month, bio8-Mean Temperature of Wettest Quarter, and bio10-Mean Temperature of Warmest Quarter). 5-Demethoxynobiletin was positively associated with both precipitation (bio12, bio17, bio19) and temperature variables (bio1-Annual Mean Temperature, bio6-Min Temperature of Coldest Month, bio9-Mean Temperature of Driest Quarter and bio11-Mean Temperature of Coldest Quarter). Cinchonain Ic was positively correlated with bio2 (Mean Monthly Temperature Range), and Oroxin A was negatively correlated with elevation. These findings demonstrated that flavonoids accumulation in F. suspensa was predominantly influenced by temperature heterogeneity, with precipitation serving as a secondary factor, while latitude and elevation play only limited roles. This study systematically investigates the divergence and environmental drivers of flavonoids in F. suspensa populations, clarifies the molecular ecological basis of its adaptation to environmental heterogeneity, and provides valuable insights for leveraging ecological factors to enhance medicinal potential, ultimately supporting targeted breeding and optimized field management strategies.