Procyanidin B1 is a polyphenolic flavonoid isolated from fruits and fruit juices, binds to TLR4/MD-2 complex, and has anti-inflammatory activity. Procyanidin B1 causes cellular toxicity at concentrations >100 μg/mL. Procyanidin B1 (100 μg/mL) inhibits LPS-induced TNF-α production, and expression of MD-2, TRAF6, NF-κB mRNA, phosphorylated p38 MAPK and NF-κB protein in THP1 cells. Procyanidin B1 (50-100 μM) protects against Aβ oligomer-induced neuronal death. Procyanidin B1 potently inhibits the activation of caspase-3 at 100 μM, caspase-8 at concentrations of 30, 50, and 100 μM and caspase-9 at concentrations of 10, 30, 50, and 100 μM. Procyanidin B1 (10, 20, 30 μM) significantly and dose-dependently induces expression of ACO and CPT1, with no obvious effect on mRNA expression of PPARα.