Immunomodulatory effects of methoxylated flavonoids from two Chromolaena species: structure-activity relationships.

Excessive generation of reactive oxygen species (ROS) by polymorphonuclear leukocytes (PMNL) is involved in the pathology of many inflammatory diseases. Compounds isolated from natural sources with antioxidant activity can be helpful to inhibit and/or modulate the oxidative damage associated with PMNL-derived ROS. The present study investigated the relationship between the chemical structure of five methoxylated flavonoids, isolated from Chromolaena hirsuta and Chromolaena squalida, and their inhibitory activity on ROS generation by opsonized zymosan-stimulated PMNL. The antioxidant efficacy of the studied flavonoids, assessed by luminol-dependent chemiluminescence, was dependent on the position and number of methoxy and hydroxy groups.