Two heretofore uncharacterised abietane diterpenes, sincoetsin C (1) and 3-hydroxyspirocoleon 7-O-β-D-glucoside (4), were isolated from a methanolic extract of Coleus blumei Benth. (Lamiaceae), along with the known compounds, scutellarioidone A (2) and spirocoleon 7-O-β-D-glucoside (3) using chromatographic techniques. Their structures were determined by 1D and 2D nuclear magnetic resonance including HSQC, HMBC, COSY and NOESY experiments, mass spectrometry (HR-MS) and other spectroscopic methods (UV, IR). Their antibacterial activity against the reference strain of methicillin-resistant Staphylococcus aureus subsp. aureus CCM 4750 (MRSA) was evaluated using optical absorption to obtain quantitative information on their growth. All isolated compounds displayed anti-MRSA 4750 activity at the concentration of 512 μg/mL. Sincoetsin C (1) was the abietane diterpene most active against MRSA 4750, with a minimum inhibitory concentration of 128 μg/mL.

Department of Molecular Biology and Pharmaceutical Biotechnology Faculty of Pharmacy University of Veterinary and Pharmaceutical Sciences Brno Brno Czech Republic

Department of Natural Drugs Faculty of Pharmacy University of Veterinary and Pharmaceutical Sciences Brno Brno Czech Republic

Department of Pharmaceutical Sciences University of Padua Padua Italy

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