A new dimeric imidazole alkaloid plasmid conjugation inhibitor from Lepidium sativum

Phytochemical investigation of the methanolic extract of Lepidium sativum seeds led to the isolation of a new compound, named 2-(3-(3-((1H-imidazol-2-yl)methyl)-5-methoxyphenoxy)benzyl)-1H-imidazole and given the trivial name Lepidine AK (1), along with three known compounds; Lepidine E (2), Lepidine B (3) and 2-(3-(2-((1H-imidazol-2-yl)methyl)-6-methoxyphenoxy)benzyl)-1H-imidazole (4). The structures were elucidated based on NMR spectroscopy, UV, IR and high-resolution electrospray ionization mass spectrometry. The isolated compounds were tested for bacterial conjugation inhibition. Lepidine AK (1, 100 μg/mL) reduced the conjugal transfer of the IncI2 plasmid TP114 to 44.7 ± 3.5% but interestingly promoted the conjugation of the IncN plasmid pKM101 to greater than 120%.