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

Two undescribed ether derivatives of sesquiterpenes, 1-ethoxycaryolane-1, 9β-diol (1) and 2-ethoxyclovane-2β, 9α-diol (3), and one new monoterpene glycoside, p-menthane-1α,2α,8-triol-4-O-β-D-glucoside (5), were obtained, together with eight known compounds from the stems and leaves ofI. simonsii. Their structures were elucidated by spectroscopic methods. Compounds1–11were evaluated for their potency againstStaphylococcus aureusand clinical methicillin-resistantS. aureus(MRSA). Among them, compound3was weakly active againstS. aureus(MIC = 128 μg/mL), and compounds6and7exhibited good antibacterial activity againstS. aureusand MRSA (MICs = 2–8 µg/mL). A primary mechanism study revealed that compounds6and7could kill bacteria by destroying bacterial cell membranes. Moreover, compounds6and7were not susceptible to drug resistance development.Keywords:Illicium simonsii;sesquiterpene;monoterpene;antibacterial;MRSA