853 JPP 2006, 58: 853–858 ß 2006 The Authors Received August 29, 2005 Accepted February 26, 2006 DOI 10.1211/jpp.58.6.0016 ISSN 0022-3573 Departamento deFı´sica e Quı ´mica, Faculdade de Cie ˆ ncias Farmace ˆ uticas de Ribeira ˜ o Preto da Universidade de Sa ˜ o Paulo, Av. do Cafe ´ s/n  , 14040-903, Ribeira ˜ o Preto – SP, Brasil Alexandre Kanashiro, Luciana M. Kabeya, Cristiane F. F. Grael, Christiane O. Jorda ˜ o, Ana Elisa C.S. Azzolini, Joa ˜ o Luis C. Lopes, Yara M. Lucisano-Valim Correspondence: Y. M. Lucisano- Valim, Departamento deFı´sica e Quı ´mica, Faculdade de Cie ˆ ncias Farmace ˆ uticas de Ribeira ˜ o Preto da Universidade de Sa ˜o Paulo – USP, Av. do Cafe ´ s/n  , 14040-903, Ribeira ˜ o Preto – SP, Brasil. E-mail: yaluva@usp.br Acknowledgment and funding: The authors thank the Brazilian agencies Fundac ¸a ˜o de Amparo a ` Pesquisa do Estado de Sa ˜ o Paulo (FAPESP) and Conselho Nacional deDesenvolvimento Cientı´fico e Tecnolo ´ gico (CNPq) for financial support to this investigation, and Dr Luciana Biagine Lopes (Faculdade de Cie ˆ ncias Farmace ˆ uticas de Ribeira ˜ o Preto de Universidade de Sa ˜ o Paulo, Ribeira ˜ o Preto-SP, Brazil) for her critical reading of the manuscript. Sesquiterpene lactones from Lychnophora pohlii: neutrophil chemiluminescence inhibition and free radical scavenger activity Alexandre Kanashiro, Luciana M. Kabeya, Cristiane F. F. Grael, Christiane O. Jorda ˜ o, Ana Elisa C.S. Azzolini, Joa ˜ o Luis C. Lopes and Yara M. Lucisano-Valim Abstract Excessive production of reactive oxygen species (ROS) by polymorphonuclear leucocytes (PMNLs) is thought to contribute to the pathology of many inflammatory diseases. Sesquiterpene lactones (STLs) seem to be important contributors to the anti-inflammatory activity of many species of Lychnophora (Asteraceae), which have been widely used in Brazilian folk medicine because of this pharmacological property. In this study, the inhibitory effects of three STLs isolated from Lychnophora pohlii (lychnopholide, centratherin and goyazensolide) on rabbit PMNL oxidative burst were evaluated by the luminol-enhanced chemiluminescence (CL-lum) assay. All STLs tested showed concentration-dependent inhibitory activity on CL-lum but were not cytotoxic to PMNLs (evaluated by lactate dehydrogenase release) under the assessed conditions. Moreover, goyazenso- lide, the most active STL, had no free radical scavenger property, as assessed by 1,1-diphenyl-2- picrylhydrazyl radical assay, and had no inhibitory effect on the luminol-horseradish peroxidase– hydrogen peroxide chemiluminescence. Taken together, the results of this investigation suggest that the concomitant presence of methacrylate ester and hydroxyl groups contributes to a high inhibitory effect on PMNL oxidative metabolism. This effect was not mediated by free radical scavenger or cytotoxic effects, but probably by inhibition of enzymes involved in the signal transduction path- ways of the ROS generation process. Introduction Polymorphonuclear leucocytes (PMNLs) or neutrophils play a crucial role in the defence of mammals against microbial infections (Johnson et al 1992). Recognition of opsonized microbes or particles via complement or antibody receptors triggers a set of effector functions of PMNLs, such as phagocytosis and production of reactive oxygen species (ROS) (Cheung et al 1983; Haas et al 1995). However, excessive release of these ROS can result in undesirable tissue and molecular damage, which have been reported as important participants in a number of inflammatory diseases, including cancer, rheumatoid arthritis, emphysema and acute respiratory distress syndrome (Weiss 1989; Babior 2000). The involvement of PMNL-derived ROS in the physio- pathology of various inflammatory illnesses has attracted the interest of many research groups trying to find new compounds to modulate inflammation and to understand the underlying mechanisms of action. Traditionally, the pharmaceutical industry has used secondary metabolites isolated from higher plants as natural sources of new drugs (Barreiro & Fraga 2001). Plants from the genus Lychnophora sp. (Asteraceae) are known as ‘arnica’ and have been widely used in Brazilian folk medicine due to their anti-inflammatory and analgesic activity (Cerqueira et al 1987; Grael et al 2000; Vieira & Martins 2000). Sesquiterpene lactones (STLs), flavonoids and triterpenes are major compounds occurring in the Lychnophora genus (Bohlmann & Jakupovic 1990). STLs display a wide variety of pharmacological and biological properties and are known to have considerable