A novel xanthone dimer derivative with antibacterial activity isolated from the bark of <i>Garcinia mangostana</i>

<p>A novel xanthone dimer derivative, garmoxanthone (<b>1</b>), together with 10 known compounds (<b>2</b>–<b>11</b>), were isolated from bark of <i>Garcinia mangostana</i>. Their structures were established through spectroscopic methods. Garmoxanthone exhibited strong inhibitory activities against MRSA ATCC 43300 and MRSA CGMCC 1.12409 (with MIC values of both 3.9 μg/mL) and moderate activities against tested strains of <i>Vibrio</i> (with MIC values ranging from 15.6 to 31.2 μg/mL). Garmoxanthone is a unique xanthone dimer with linkage of a fused 5/6 ring system and its absolute configuration was elucidated on the basis of experimental and calculated electronic circular dichroism. Garmoxanthone exhibited strong antibacterial activity which partially validated the ethnobotanical use of <i>G. mangostana</i> in the treatment of infections.</p>