Two isoquinoline alkaloids isolated from the leaves of Monodora tenuifolia Benth. (Annonaceae)

Monodora tenuifolia is a species of plant in the Annonaceae family native to Africa. The Monodora genus contains isoquinoline alkaloids, compounds known for their many therapeutic properties. These are chemotaxonomic markers of the genus. This study describes the isolation and identification of two isoquinoline alkaloids from the leaves of Monodora tenuifolia Benth. (Annonaceae). Structural analysis was performed using one-dimensional nuclear magnetic resonance (¹H and ¹³C NMR) and two-dimensional COSY, HSQC, HMBC, and NOESY techniques. The spectra obtained enabled the compounds to be formally identified as (-)-N-methylarmepavine, a benzylisoquinoline, and (+)-listeferine, an oxoaporphine. These results constitute the first evidence of these two alkaloids in the leaves of M. tenuifolia. The study also highlights the correlations between these structures and their known pharmacological properties, such as the antioxidant, antimicrobial, and neuroprotective activities reported in the literature. These data contribute to the enrichment of the chemical profile of the Monodora genus and provide a solid foundation for future biological investigations.