Sorocenols G and H, Anti-MRSA Oxygen Heterocyclic Diels-Alder-Type Adducts from Sorocea muriculata Roots

Bioassay-guided fractionation of a root extract of Sorocea muriculata led to the isolation and identification of two new oxygen heterocyclic Diels-Alder-type adducts, sorocenols G (1) and H (2), along with lupeol-3-(3'R-hydroxytetradecanoate) and oxyresveratrol. The structures of 1 and 2 were elucidated using 1D and 2D NMR spectroscopic and HRMS data and by comparison with reported values. The absolute configurations of I and 2 were established by analysis of their experimental and theoretically calculated CD spectra. Compounds I and 2 showed significant and selective activity against methicillin-resistant Staphylococcus aureus with IC(50) values of 1.5 and 0.5 mu M, respectively. Compound 2 also displayed antifungal activity against Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus, with IC50 values of 5.4, 5.4, and 10.0 mu M, respectively.