A new phloroglucinol derivative and anti-MRSA active phloroglucinols from Hypericum mutilum L. (Clusiaceae)

In the present investigation the secondary metabolites of Hypericum mutilum L. (Clusiaceae, sect. Trigynobrathys), a native plant of Eastern North America, were studied. In an antibacterial screening against gram-positive and gram-negative bacteria, the dichloromethane extract of H. mutilum was found to exhibit a strong inhibitory activity against Staphylococcus aureus and St. epidermidis in the disk diffusion assay. During the phytochemical analysis, several phloroglucinol derivatives carrying these strong antibacterial activities were isolated and structurally elucidated. Among these, the known uliginosins A and B (1) together with a hitherto unknown phloroglucinol of isouliginosin type (2) were found. Uliginosin A and B showed at a concentration of 10µg considerable activity against the methicillin-resistant St. aureus MRSA NCTC 10442 PVL (-) with inhibition zones of 1.5 and 5mm, respectively.

Uliginosin A and B were first described from H. uliginosum H.B.K. [1], later also found in other members of the section Trigynobrathys. This is the first report on their activity against methicillin-resistant St. aureus.

References: [1] Taylor, HL et al. (1969) Lloydia 32: 217–19