Extracts of Penstemon gentianoides inhibit lipopolysaccharide‐induced expression of inducible nitric oxid synthase and cyclooxygenase‐2 in murine macrophage RAW 264.7 cells

Abstract

The leaves from Penstemon gentianoides have been used traditionally for the treatment of inflammatory diseases in Mexican medicine. A methanol extract of these leaves has both a high oxygen radical absorbance capacity (an in vitro measure of antioxidant activity) and a high content of polyphenolic compounds (thought to provide antioxidant activity). Since oxidative stress is thought causative in the inflammatory response, we looked to see if extracts could lower generation of reactive oxygen species (ROS) in response to lipopolyssacharide (LPS) in murine macrophages RAW 264.7, and decrease resulting expression of inducible nitric oxide synthase (iNOS) and/or cyclooxygenase-2 (COX-2). iNOS and COX-2 expression was analyzed by Western blot and generation of intracellular oxidative stress / ROS was measured by colorimetric assay using 2′,7-dichlorofluorescein diacetate. Treatment of RAW 264.7 cells with hexane or methanol extracts decreased LPS-induced ROS generation and iNOS expression, but increased COX-2 expression. Treatment with a dicholomethane extract also decreased ROS generation, although it decreased iNOS expression and increased COX-2 expression. These data clearly show the need for consistent formulation and preparation of herbal extracts such as those of P. gentianoides, since different extracts can have very different effects within the cell. This work was supported by a grant from US AID.