Procyanidin A2 is a natural flavanol dimer of (-)-epicatechin that is found in the horse chestnut (A. hippocastanum), mountain cranberry (V. vitis-idaea), and other fruits with antioxidant, anti-inflammatory, antibacterial, antiproliferative, and antidiabetic properties. It scavenges 2,2-diphenyl-1-picrylhydrazyl radicals (IC50 = 5.08 μM) and inhibits STAT3 activation induced by platelet derived growth factor (PDGF) in primary rat vascular smooth muscle cells (VSMCs) when used at a concentration of 30 μg/ml. Procyanidin A2 inhibits growth of S. aureus and E. coli (MICs = 62.5 and 62.5 μg/ml, respectively) and proliferation of human HepG2 liver hepatocellular carcinoma and HeLa cervical cancer cells (EC50s = 62.19 and 66.07 μg/ml, respectively). It also increases insulin secretion from primary mouse pancreatic islets when used at a concentration of 10 μM in vitro and inhibits bisphenol A-induced glucose increases in fasted mice when administered at a dose of 10 μmol/kg per day.