Isoprenylated phenolic compounds with tyrosinase inhibition from <i>Morus nigra</i>

<p>A new isoprenylated sanggenon-type flavanone, nigrasin K (<b>1</b>), together with three known analogs (<b>2</b>–<b>4</b>) and five known Diels–Alder adducts (<b>5</b>–<b>9</b>), were isolated from the twigs of <i>Morus nigra</i>. Their structures were elucidated by spectroscopic methods. Sanggenon M (<b>2</b>), chalcomoracin (<b>5</b>), sorocein H (<b>6</b>), kuwanon J (<b>7</b>), sanggenon C (<b>8</b>), and sanggenon O (<b>9</b>) showed significant inhibitory effects on mushroom tyrosinase.</p>