Thrysaxinones A–F: antibacterial phloroglucinol-terpenoid adducts from Thryptomene saxicola

Abstract

Thrysaxinones A–F (1–6), six new phloroglucinol-terpenoid adducts (PTAs), were isolated from Thryptomene saxicola. Their structures and absolute configurations were elucidated by extensive spectroscopic analysis, X-ray crystallography, and quantum chemical calculations. Compounds 1–3 represent unprecedented PTAs with gorgonane- or oplopane-type sesquiterpenoid moieties. Notably, compound 1 features an unusual 11-oxa-tricyclo[6.2.1.0^4,9]undecane core. Compound 4 is a unique PTA with a new carbon skeleton formed by an acylphloroglucinol unit coupled with a bicyclogermacrene-type sesquiterpenoid moiety. The plausible biogenetic pathways for compounds 1–6 were proposed. Moreover, compounds 1, 2, 5, and 6 exhibited significant antibacterial activities against clinical methicillin-resistant Staphylococcus aureus (MRSA) strains. Compound 1, the most potent one, could rapidly and effectively eradicate bacteria by inducing hyperpolarization and disrupting cell membrane integrity.