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RESEARCH PRODUCT

Natural Triterpenoids as Anti-Inflammatory Agents

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Abstract This chapter reviews the natural triterpenes with anti-inflammatory activity, including the traditional ones and the new compounds isolated over the last six years. Triterpenes are widely distributed in plants, and in many cases are the principles responsible for their anti-inflammatory effects. Many of these compounds are active in different in vivo experimental models such as hind paw edema induced by carrageenan, serotonin and phospholipase A2; ear edema induced by phorbol and daphnane esters, ethylphenylpropiolate, arachidonic acid and capsaicin; adjuvant arthritis and experimental models of allergy. Other effects have been studied in vitro, and some triterpenes are active against inflammatory enzymes like 5-lipoxygenase, elastase and phospholipase A2. Others inhibit histamine, collagenase and interleukin release, lipid peroxidation and free radical-mediated processes, metabolism of endogenous corticoids, and complement and protein-kinase activities. In certain cases the mechanism of action depends on the skeleton type and/or substituents. For example, β-boswellic acid (ursane-derived) and derivatives markedly inhibit 5-lipoxygenase activity, whereas the principal mechanism of 18β-glycyrrhetinic acid (oleanane-derived) is the inhibition of endogenous corticoid metabolism. Some lanostanes are active against phospholipase A2 (e.g. ganoderic and dehydrotumulosic acids), and compounds with highly unsaturated rings can act as anti-peroxidatives (e.g. celastrol, a tetraunsaturated friedooleanane).