Phytotoxic activity of Bidens pilosa extracts and predicted interactions of selected allelochemicals with germination-related hydrolytic enzymes

This study evaluated the growth-inhibitory activity and possible chemical basis of extracts derived from leaves, stems, and flowers of Bidens pilosa against three weed species ( Cynodon dactylon , Echinochloa crus-galli , and Oryza sativa f. spontanea ) and the bioindicator species Brassica integrifolia . Leaf extracts showed the strongest inhibitory activity, with radicle growth being more sensitive than shoot growth, and the inhibitory effects generally followed the order leaves > flowers > stems. Multivariate analysis revealed clear differences in the chemical composition among plant parts. Leaves had the highest total phenolic (45.32 mg/g dry weight) and flavonoid (17.06 mg/g dry weight) contents. HPLC-PDA, interpreted as external-standard-based apparent extractable concentrations, indicated that leaves yielded high levels of epicatechin, chlorogenic acid, and veratric acid, whereas flowers were characterized by catechin and epigallocatechin gallate (EGCG). Molecular docking of 12 allelochemicals against eight germination-related hydrolytic enzymes predicted favorable binding profiles for EGCG and chlorogenic acid with β-amylase, invertase, and carboxypeptidase, with binding energies ranging from -9.0 to -9.6 kcal/mol and docking-derived Ki estimates < 1 µM. These docking outputs are hypothesis-generating computational evidence only and do not demonstrate enzyme inhibition. Overall, B. pilosa leaf extracts represent a promising source for bioherbicide-oriented research, but purified-compound bioassays, enzyme inhibition assays, and recovery-corrected quantification are needed to validate the proposed mechanisms and active compounds.