Sesquiterpenes and Monoterpenes from the Leaves and Stems of Illicium simonsii and Their Antibacterial Activity.

Two undescribed ether derivatives of sesquiterpenes, 1-ethoxycaryolane-1, 9 β -diol ( 1 ) and 2-ethoxyclovane-2 β , 9 α -diol ( 3 ), and one new monoterpene glycoside, p-menthane-1 α ,2 α ,8-triol-4-O- β -D-glucoside ( 5 ), were obtained, together with eight known compounds from the stems and leaves of I. simonsii . Their structures were elucidated by spectroscopic methods. Compounds 1 - 11 were evaluated for their potency against Staphylococcus aureus and clinical methicillin-resistant S. aureus (MRSA). Among them, compound 3 was weakly active against S. aureus (MIC = 128 μg/mL), and compounds 6 and 7 exhibited good antibacterial activity against S. aureus and MRSA (MICs = 2-8 µg/mL). A primary mechanism study revealed that compounds 6 and 7 could kill bacteria by destroying bacterial cell membranes. Moreover, compounds 6 and 7 were not susceptible to drug resistance development.