Inhibition of leukotriene biosynthesis by secondary plant metabolites

Leukotrienes (LTs) are a group of biologically highly potent mediators of inflammation, synthesised in the first metabolic step by 5-lipoxygenase from 20 carbon fatty acids, predominantly arachidonic acid. They include the cysteinyl leukotrienes LTC4, LTD4, LTE4, which cause bronchoconstriction, chemotaxis and enhanced blood vessel-permeability, and therefore play a major role in asthma, and the dihydroxyeicosatetraenoate LTB4, an important mediator for acute and chronic inflammatory ailments. Inhibition of leukotriene biosynthesis therefore is a promising target for combating a number of diseases. Plant secondary metabolites offer a structurally very diverse potential source of new therapeutic leads. The aim of this review is to update the current knowledge of plant compounds with inhibitory effects on leukotriene metabolism, by presenting results published in the last seven years. Substances are presented with their IC50 values together with the activities of the positive controls to enable better comparability. Inhibitory effects of extracts are not discussed.