Isolation, identification, and antimicrobial effect analysis of active components from Humulus scandens against Phytophthora nicotianae

Monomeric compounds from <i>Humulus scandens</i> that effectively inhibit <i>Phytophthora nicotianae</i> were isolated, and their antimicrobial effects were analyzed. Methanol extracts were isolated using a combination of activity tracking and chemical separation methods. Compound structures were identified using NMR and other techniques. Antimicrobial activity against <i>P. nicotianae</i> was assessed via the mycelial growth rate method with mycelial morphology further observed using optical microscopy and scanning electron microscopy. Five compounds were isolated from the ethyl acetate (EtOAc) layer of <i>H. scandens</i>, namely, chromone (compound 1), tectochrysin (compound 2), isorhamnetin (compound 3), hyperoside (compound 4), and Apigenin 7-glucoside (compound 5). All compounds exhibited varying degrees of antimicrobial activity. Compounds 1 and 5 demonstrated superior inhibitory effects, with EC₅₀ values of 51.70 and 31.71 μg/ml and MIC values of 400 and 200 μg/mL, respectively. Microscopic examination revealed that compounds 1 and 5 induced distortion, deformation, shrinkage, collapse, and damage in <i>P. nicotianae</i> mycelia. Additionally, they increased membrane permeability and inhibited mycelial growth by disrupting cellular integrity. This study provides lead compounds for developing green botanical pesticides against tobacco black shank disease and offers data to support green agriculture initiatives.