Evaluation of nitric oxide scavenging activity, In Vitro and Ex Vivo , of selected medicinal plants traditionally used in inflammatory diseases

Steroidal and non‐steroidal antiinflammatory drugs, despite their various side effects, are in great demand worldwide. Alternatively, herbal formulations provide relief to a large percentage of the population suffering from inflammatory diseases. Therefore, such practices need to be rationalized through a mechanistic approach. Thus, four traditional medicinal plants, namely Ventilago madraspatana Gaertn., Rubia cordifolia Linn., Lantana camara Linn. and Morinda citrifolia Linn. were selected for a study on the inhibition of nitric oxide (NO • ), a key mediator in the phenomenon of inflammation, signifying the presence of effective antiinflammatory constituents therein. Plant samples were extracted with different solvents for evaluation of their inhibitory activity on NO • produced in vitro from sodium nitroprusside, and in LPS‐activated murine peritoneal macrophages, ex vivo . Further, the inhibition of NO • synthesis was correlated with the reduction of iNOS protein expression through Western blot. Notable NO • scavenging activity was exhibited in vitro by some extracts of V. madraspatana , R. cordifolia and L. camara (IC 50 < 0.2 mg/mL). Most of them showed marked inhibition (60%–80%), ex vivo , at a dose of 80 µg/mL without appreciable cytotoxic effect on the cultured macrophages. Immunoblot analysis confirmed that the modulatory effect of the samples had occurred through suppression of iNOS protein. Copyright © 2006 John Wiley & Sons, Ltd.