Morphological, genetic, and phenolic characterization of Baccharis glutinosa and Baccharis salicifolia and their application in the biogenic synthesis of silver nanoparticles

The genus Baccharis exhibits high taxonomic diversity and marked morphological plasticity, which complicates the species-level delimitation of closely related taxa. In this study, an integrated characterization of Baccharis glutinosa and Baccharis salicifolia collected in the La Libertad region, Peru, was conducted by combining morphological, molecular, and phytochemical evidence, together with their biotechnological application in the biogenic synthesis of silver nanoparticles (AgNPs). Botanical identification was based on foliar, floral, and palynological characters, while DNA barcoding analyses using the matK and rbcL markers confirmed the assignment of both species to the genus Baccharis , revealing a higher species-level discriminatory power for matK and a lower resolution of rbcL among closely related species. In parallel, the extracts were characterized through total phenolic content (TPC), antioxidant capacity (AC), HPLC-DAD chromatographic fingerprinting, and UHPLC-MS/MS analysis, revealing distinct phenolic profiles between both Baccharis species. B. glutinosa exhibited significantly higher TPC and AC levels than B. salicifolia , which was reflected in a greater reducing efficiency during the biogenic synthesis of AgNPs. The resulting nanoparticles were characterized by UV-Vis spectroscopy, X-ray diffraction, Raman spectroscopy, and colloidal analysis (DLS and zeta potential), confirming the formation of crystalline AgNPs with a face-centered cubic structure, good colloidal stability, and smaller hydrodynamic sizes in systems derived from B. glutinosa . The optimized extracts and their corresponding silver nanoparticles were further evaluated against Listeria monocytogenes , revealing enhanced antibacterial activity for the nanoparticle formulations compared with the crude extracts.