Abstract
•South Africa is considered a centre of diversity for the genus Plectranthus.•Two natural acetophenones were isolated from the leaves of Plectranthus venteri.•Both compounds exhibited the ability to inhibit the transfer of the IncW plasmid R7K between strains of Escherichia coli in a plasmid transfer inhibition assay.•Structure elucidation was achieved by NMR spectroscopy and HRTOFESIMS.
In a project to investigate the chemistry of South African Plectranthus species, from the dichloromethane extract of the aerial parts of Plectranthus venteri, we isolated two known natural product acetophenones, namely 2-hydroxy-3,4,5,6-tetramethoxy-acetophenone (1) and 2-hydroxy-4,5,6-trimethoxy-acetophenone (2). Structures were assigned using NMR spectroscopy and HRTOFESIMS. Compound 1 was previously synthesised as a precursor to the polymethoxylated flavone nobiletin. The acetophenones exhibited remarkable inhibitory activities against the transfer of the IncW plasmid R7K in a bacterial plasmid transfer inhibition assay.