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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-Noxide (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. [ABSTRACT FROM AUTHOR]

The grain contamination by Aspergillus spp. has been a serious issue. This study exhibited the excellent antifungal effects of the essential oil compounds (EOCs) geraniol and citral against common grain pathogens (A. flavus and A. ochraceus) in vitro and in situ. The inhibitory mechanisms were also evaluated from the perspective of cell membrane permeability, reactive oxygen species (ROS) generation, and Aspergillus spp. growth-related gene expression. Meanwhile, the combined effects of EOCs in the vapor phase and modified atmosphere packaging (MAP) were examined to find an alternative preservation method for controlling Aspergillus spp. The results indicated that citral exhibited the antifungal activity mainly by downregulating the sporulation- and growth-related genes for both pathogens. Geraniol displayed inhibitory effectiveness against A. flavus predominantly by inducing the intracellular ROS accumulation and showed toxicity against A. ochraceus principally by changing cell membrane permeability. Furthermore, the synthetic effects of EOCs and MAP (75% CO2 and 25% N2) induced better grain quality than the current commercial fumigant AlP. These findings reveal that EOCs have potential to be a novel grain preservative for further application. [ABSTRACT FROM AUTHOR]