%0 Journal Article %T Four New Antibacterial Xanthones from the Marine-Derived Actinomycetes Streptomyces caelestis %A Ling-Li Liu %A Ying Xu %A Zhuang Han %A Yong-Xin Li %A Liang Lu %A Pok-Yui Lai %A Jia-Liang Zhong %A Xian-Rong Guo %A Xi-Xiang Zhang %A Pei-Yuan Qian %J Marine Drugs %D 2012 %I MDPI AG %R 10.3390/md10112571 %X Four new polycyclic antibiotics, citreamicin ¦È A ( 1), citreamicin ¦È B ( 2), citreaglycon A ( 3), and dehydrocitreaglycon A ( 4), were isolated from marine-derived Streptomyces caelestis. The structures of these compounds were elucidated by 1D and 2D NMR spectra. All four compounds displayed antibacterial activity against Staphylococcus haemolyticus, Staphylococcus aureus, and Bacillus subtillis. Citreamicin ¦È A ( 1), citreamicin ¦È B ( 2) and citreaglycon A ( 3) also exhibited low MIC values of 0.25, 0.25, and 8.0 ¦Ìg/mL, respectively, against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300. %K Streptomyces caelestis %K citreamicin %K antibacterial %K MRSA %U http://www.mdpi.com/1660-3397/10/11/2571