A new isoprenylated sanggenon-type flavanone, nigrasin K (1), together with three known analogs (2-4) and five known Diels-Alder adducts (5-9), were isolated from the twigs of Morus nigra. Their structures were elucidated by spectroscopic methods. Sanggenon M (2), chalcomoracin (5), sorocein H (6),