A new L-proline derivative, monophyllidin (1), together with four known compounds, thalifoline (2), berberine (3), jathrorrhizine (4) and 3b-glucositosterol (5) has been isolated from the bark of Zanthoxylum monophyllum. The structure of compound 1 was elucidated on the basis of extensive spectroscopic data analysis. Characterization of compounds 2–5 was based on spectral analysis and comparison with reported data. Compound 3 showed antibacterial activity against the five bacterial strains used, while 1, 4 and 5 presented only antibacterial activity against Enterococcus faecalis. Compounds 2 and 4 showed antifungal activity, with 100 mg against Fusarium oxysporum f. sp. lycopersici.