Calycosin is an isoflavone and phytoestrogen with diverse biological activities.^1,2,3,4,5,6 It is an estrogen receptor (ER) partial agonist that inhibits 17β-estradiol binding to ERα and ERβ (IC50s = 83.14 and 40.38 μM, respectively).¹ Calycosin induces tube formation by human umbilical vein endothelial cells (HUVECs) in a Matrigel™ assay and angiogenesis in zebrafish via activation of ERs and ERK1/2. It has antiplasmodial and antiprotozoal activities, reducing the growth of the poW and Dd2 strains of P. falciparum (IC50s = 4.2 and 9.8 μg/ml, respectively) and exhibiting selective toxicity for T. brucei brucei over Vero cells (IC50s = 12.7 and 159 μM, respectively).^2,3 Calycosin scavenges 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals in a cell-free assay and inhibits xanthine/xanthine oxidase-induced toxicity in PC12 cells (EC50 = 50 ng/ml).⁴ In vivo, calycosin (12.5 and 25 mg/kg) reduces alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity, triglyceride accumulation, and hepatic fibrosis in a mouse model of non-alcoholic steatohepatitis (NASH).⁵ It also decreases infarct volume and brain edema in a rat model of focal cerebral ischemia and reperfusion injury.⁶