Studies were conducted to determine and identify the molecular principles or compounds responsible for the notoriously reported negative (inhibitory) allelopathic effect of Chromolaena odorata on the germination of both monocotyledonous and dicotyledonous seeds. The aqueous extract of Chromolaena odorata leaves were subjected to GC-MS analysis, and 46 compounds were profiled from the extract. Using ArgusLab, these compounds profiled by means of GC-MS were subjected to in silico molecular docking targeting an amylase (α-amylase) and a protease (asparaginyl endopeptidase), the key enzymes necessary for starch and protein hydrolyses during germination. The compounds Retinal (Vitamin A aldehyde) showed the least binding energy for α-amylase (-13.5992 kcal/mol) compared to Maltose which showed no acceptable ligand pose; while the compound Tetradecane showed the least binding energy for asparaginyl endopeptidase (-12.6293 kcal/mol) compared to (1R,8S)-bicyclo[6.1.0]nonane (a docked residue in the PDB crystal structure) with binding energy of -9.60911 kcal/mol. This study suggests, therefore, that the inhibitory allelopathic effect of Chromolaena odorata on seed germination may be due to the presence of retinaldehyde and tetradecane in the aqueous extract that non/competitively inhibit the functions of α-amylase and cysteine proteinases respectively. Aside proffering a molecular explanation to the inhibitory allelopathy of Chromolaena odorata on germinating seeds, this finding has great commercial prospects in the formulation of eco-friendly pre-emergence herbicides and/or the design of preservatives for seed storage.
