Morushalunin D, a tri- O -bridged Diels-Alder type adduct from Morus alba var. shalun root cultures and the related precursors.

Three Diels-Alder type adducts ( 1 - 3 ) along with their precursors, including one 2-arylbenzofuran ( 4 ) and one stilbene ( 5 ), were isolated from the MeOH extract of M. alba var. shalun root cultures. Among them, 1 is a new Diels-Alder type adduct named morushalunin D. The molecular structures of 1 - 5 were elucidated based on spectroscopic data and comparison with the literatures. Cytotoxic properties of compounds 1 - 5 were evaluated against murine leukemia P-388 cells. Morushalunin D ( 1 ), mulberrofuran T ( 2 ), sorocein A ( 3 ), moracin M ( 4 ), and oxyresveratrol ( 5 ) were active, significantly inhibiting the growth of P-388 cells with IC 50 values of 0.5, 1.0, 0.6, 2.0, and 3.3 μg/ml, respectively.