Emerones A-C: three novel merosesquiterpenoids with unprecedented skeletons from Emericella sp. XL029

Three novel highly oxygenated α-pyrone merosesquiterpenoids, emerones A-C (1-3), have been obtained from the fungus, Emericella sp. XL029, which was isolated from the leaves of the traditional Chinese medicinal plant, Panax notoginseng. The structures and absolute configurations of 1-3 were determined by NMR experiments, X-ray diffraction analysis, and computational methods. Structurally, compound 1 possessed an unprecedented 5/7 bicyclic ring architecture, compound 2 had an unusual substituted 10-membered ring, and compound 3 had an undescribed norsesquiterpene skeleton. In addition, compounds 1 and 2 showed moderate activity towards several types of bacteria and fungi, exhibiting MIC values ranging from 12.5 to 50 μg mL^-1, whereas compound 3 showed no antimicrobial activity.