Morusin is a prenylated flavonoid that has been found in M. alba and has diverse biological activities, including enzyme inhibitory, anti-inflammatory, and antiproliferative properties.^1,2,3,4 It inhibits the UDP-glucuronosyltransferase (UGT) isoforms UGT1A6, UGT1A7, and UGT1A8 (IC50s = 4.23, 0.98, and 3 μM, respectively) and the cytochrome P450 (CYP) isoforms CYP3A4, CYP1A2, CYP2C9, and CYP2E1 (IC50s = 2.13, 1.27, 3.18, and 9.28 μM, respectively).¹ Morusin (4 μM) inhibits histamine and leukotriene C4 (LTC4) production induced by A23187 and phorbol 12-myristate 13-acetate (PMA) in mouse MC/9 mast cells.² It also inhibits the growth of MCF-7, MDA‑MB‑231, and MDA‑MB‑453 breast cancer cells (IC50s = 13.53, 10.84, and 11.99 μM, respectively).³ Morusin (12.5 mg/kg per day) decreases colonic tissue damage, TGF-β1 levels, and matrix metalloproteinase-2 (MMP-2) and MMP-9 activity in a rat model of TNBS-induced ulcerative colitis.⁴