Potential cytotoxic Diels-Alder type adducts from liquid medium of Morus Alba var. shalun root cultures

A new Diels-Alder type adduct named morushalunin (1), together with three similar compounds, guangsangon E (2), chalcomoracin (3), and kuwanon J (4) were isolated from the EtOAc extract of liquid medium of Morus alba var. shalun root cultures. The structures of the isolated compounds were determined based on spectroscopic data, including 1D, 2D NMR, and MS data. Cytotoxic properties of compounds 1-4 were evaluated against murine leukemia P-388 cells. Morushalunin (1), guangsangon E (2), and chalcomoracin (3) were found to have significant cytotoxicity with IC₅₀ values 0.7, 2.5, and 1.7 μg/mL, respectively, while kuwanon J (4) showed weak cytotoxicity (IC₅₀ = 5.9 μg/mL).