Methicillin-Resistant Staphylococcus aureus (MRSA)-Active Metabolites from Platanus occidentalis (American Sycamore)

One known and three new potent, selective, and nontoxic anti-MRSA metabolites, kaempferol 3-O-alpha-L-(2 '',3 ''-di-E-p-coumaroyl)rhamnoside (1) (IC50 2.0 mu g/mL), kaempferol 3-O-alpha-L-(2 ''-E-p-coumaroyl-3 ''-Z-p-coumaroyl)rhamnoside (2) (IC50 0.8 mu g/mL), kaempferol 3-O-alpha-L-(2 ''-Z-p-coumaroyl-3 ''-E-p-coumaroyl)rhamnoside (3) (IC50 0.7 mu g/mL), and kaempferol 3-O-alpha-L-(2 '',3 ''-di-Z-p-coumaroyl)rhamnoside (4) (IC50 0.4 mu g/mL), were isolated from the leaves of the common American sycamore, Platanus occidentalis. Compounds 2-4 are new. Due to the unusual selectivity, potency, and safety of the pure compounds and the semipure glycoside mixture against MRSA, it is clear that this represents a viable class of inhibitors to prevent growth of MRSA on surfaces and systemically.