Isolation of antofine from Cynanchum atratum BUNGE (Asclepiadaceae) and its antifungal activity against Penicillium digitatum

The present study describes the isolation of the alkaloid antofine from Cynanchum atratum BUNGE as well as its anti-fungal potential against the citrus postharvest pathogen Penicillium digitatum. Antofine, which was extracted using an ultrasonic-assisted method and identified by H-1, C-13-NMR, and LC/MS analysis, showed strong antifungal activity against P. digitatum, with an observed minimum inhibitory concentration (MIC) and a minimum fungicidal concentration (MFC) of 1.56 x 10(-3) and 1.25 x 10(-2) g L-1, respectively. In vivo assays showed that antofine could significantly reduce the incidence of green mold. Furthermore, the total lipid and ergosterol contents of P. digitatum decreased after antofine treatment, indicating the disruption of membrane integrity. In addition, antofine caused a significant reduction of the intracellular adenosine triphosphate (ATP) content during the entire exposure period. These results suggest that the antifungal activity of antofine against P. digitatum can be attributed to the disruption of the cell membrane integrity and energy metabolism.