Antifungal activity and synergic effect of Ageratum conyzoides L. in association with amphotericin B

Considering the increasing incidence of Candida infections and the reduced efficacy of current antifungals, this study evaluated the activity of the essential oil (EOAc) and crude hydroalcoholic extract (CEAc) of Ageratum conyzoides and their synergism with amphotericin B. EOAc and CEAc were chemically characterized by GC-MS and LC-MS, respectively. MICs were determined by broth microdilution (CLSI M27-A4), and interactions assessed by the checkerboard method. Precocene I (69.4 %) and caryophyllene (8.5 %) were the main EOAc constituents, while lignans such as syringaresinol, schisandrol A, and medioresinol predominated in CEAc. EOAc inhibited C. albicans , C. parapsilosis , and C. tropicalis with MICs of 62.5, 31.25, and 7.8 µg/mL, respectively, whereas CEAc showed MICs of 31.25 µg/mL ( C. albicans ) and 15.62 µg/mL ( C. parapsilosis and C. tropicalis ). Synergistic effects with amphotericin B were observed (FICI 0.18–0.37). Literature reports support antifungal activity of syringaresinol, medioresinol, caffeic acid derivatives, and coumarins, compounds identified in CEAc. These findings highlight the potential of A. conyzoides as an adjuvant in antifungal therapy. • EOAc and CEAc of Ageratum conyzoides showed antifungal activity against Candida spp. • First report of synergism of EOAc and CEAc with amphotericin B against Candida . • CEAc rich in lignans and EOAc rich in precocene I were chemically characterized. • Findings highlight potential of natural products as antifungal adjuvants.