Procyanidin C1 is a polyphenol flavonoid trimer of (-)-epicatechin that has HIV-related and antioxidant activities. It activates latent HIV-1 provirus in JLR2 cells when used at concentrations ranging from 12.5 to 50 μM and increases NF-κB-dependent transcriptional activity in Jurkat T cells. Procyanidin C1 also scavenges 2,2'-diphenyl-1-picrylhydrazyl (DPPH) radicals (IC50 = 3.2 μg/ml) and inhibits the activity of α-glucosidase (IC50 = 3.8 μg/ml) and 15-lipoxygenase (15-LO; IC50 = 57.6 μg/ml). Procyanidin C1 (10 μg/ml) prevents phosphorylation of ERK1/2 and the production of reactive oxygen species (ROS) in THP-1 cells.