Antibacterial, antifungal and cytotoxic isoquinoline alkaloids from Litsea cubeba

Abstract

Five novel isoquinoline alkaloids (+)-N-(methoxylcarbonyl)-N-nordicentrin (1), (+)-N-(methoxylcarbonyl)-N-norpredicentrine (2), (+)-N-(methoxylcarbonyl)-N-norbulbodione (3), and (+)-N-(methoxylcarbonyl)-N-norisocorydione (4), and (+)-8-methoxyisolaurenine-N- oxide (5) were isolated, together with one known compound, (+)-N-(methoxylcarbonyl)- N-norglaucine (6), from a 70% EtOH extract of the barks of Litsea cubeba. Structural elucidation of all the compounds were performed by spectral methods such as 1D- and 2D-NMR, IR, UV, and HRESIMS. Alkaloids 1, 2 and 6 showed antimicrobial activity against the bacterium S. aureus and two fungi (A. alternata and C. nicotianae). Compounds 3,4 exhibited significant cytotoxicity against all of six tested tumor cell lines.