Anti-Oxidant, Anti-Inflammatory and Anti-Allergic Activities of Luteolin

Abstract

Luteolin is a flavone which occurs in medicinal plants as well as in some vegetables and spices. It is a natural anti-oxidant with less pro-oxidant potential than the flavonol quercetin, the best studied flavonoid, but apparently with a better safety profile. It displays excellent radical scavenging and cytoprotective properties, especially when tested in complex biological systems where it can interact with other anti-oxidants like vitamins. Luteolin displays specific anti-inflammatory effects at micromolar concentrations which are only partly explained by its anti-oxidant capacities. The anti-inflammatory activity includes activation of anti-oxidative enzymes, suppression of the NFκB pathway and inhibition of pro-inflammatory substances. In vivo , luteolin reduced increased vascular permeability and was effective in animal models of inflammation after parenteral and oral application. Although luteolin is only a minor component in our nutrition (less than 1 mg/day) epidemiological studies indicate that it has the potential to protect from diseases associated with inflammatory processes such as cardiovascular disease. Luteolin often occurs in the form of glycosides in plants, but these are cleaved and the aglycones are conjugated and metabolized after nutritional uptake which has to be considered when evaluating in vitro studies. Some data for oral and topical bioavailability exist, but more quantitative research in this field is needed to evaluate the physiological and therapeutical potential of luteolin. Abbreviations Akt:serine/threonin protein kinase B COX-2:cyclooxygenase-2 CVD:cardiovascular disease DPPH:2,2-diphenyl-1-picrylhydrazyl EAE:experimental autoimmune encephalomyelitis EGCG:epigallocatechin 3-gallate fMLP:fMetLeuPhe, formyl peptide GSH:glutathione IFN-γ:interferon γ IκB:Inhibitor of kappa B IL:interleukin iNOS:inducible nitric oxygen synthase IP-10:inducible nitric oxygen synthase IRF:interferon regulatory factor LPS:lipopolysaccharide LysoPAF AcTF:1-lysophospholipide acetyltransferase MAPK:mitogen-activated protein kinase M-CSF:macrophage colony-stimulating factor NFκB:nuclear factor kappa B 8-OHdG:8-hydroxy-2′-deoxyguanosine PGE 2 :prostaglandin E 2 PMA:phorbol myristate acetate ROS:reactive oxygen species TEAC:trolox equivalent anti-oxidant capacity TNF-α:tumor necrosis factor-α