Bioassay-directed fractionation using multidrug-resistant (MDR) Staphylococcus aureus resulted in the isolation of four new polyprenylated benzophloroglucinol derivatives, sampsoniones N-Q (1-4), and four known compounds, 7-epiclusianone (5) and sampsoniones B, L, and R, from the roots of Hypericum sampsonii. The structures of these compounds were established by analysis of spectroscopic data, and the structures of 4 and 5 were determined by single-crystal X-ray diffraction crystallography. In the bioassay, 7-epiclusianone (5) showed promising activity with a minimum inhibitory concentration (MIC) of 7.3 microM against the NorA overexpressing MDR S. aureus strain SA-1199B; the positive control antibiotic norfloxacin showed activity at MIC 100 microM.

Two new norlignans, hyperiones A (1) and B (2), three new acylphloroglucinols, aspidinol C (3) and hyperaspidinols A (5) and B (6), the known compound aspidinol D (4), and the symmetrical dimeric xanthone hyperidixanthone (7) were isolated from Hypericum chinense. Their structures were established by spectroscopic analysis. In an antibacterial assay using a panel of multidrug-resistant (MDR) strains, compounds 3 and 4 exhibited promising activity against the NorA efflux protein overexpressing MDR Staphylococcus aureus strain SA-1199B with a minimum inhibitory concentration (MIC) of 2 μg/mL (8.4 μM) and 4 μg/mL (16.8 μM), respectively. The positive control antibiotic norfloxacin showed activity at MIC 32 μg/mL (100 μM).

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