Rosmarinic acid is a naturally-occurring phenolic compound with antioxidant and anti-inflammatory properties. This compound inhibits lipid peroxidation of rat liver microsomes by 90% at a concentration of 25 μg/ml.{4778} Rosmarinic acid suppresses endotoxin-induced activation of complement and concomitant formation of prostacyclin.{4407,4408} Formation of 5-HETE and LTB4 from human PMNL is inhibited by rosmarinic acid at concentrations of 10-5 to 10-3 M.{4706}