Vernonia cinerea Less. or little iron weed has many therapeutic properties such as antipyretic and anti-inflammatory effects, thus being applied for Thai traditional medicine. Nevertheless, no scientific data on anti-inflammatory effect in humans is found. Herein, the present study aimed at assessing the toxicity of the methanolic extract of Vernonia cinerea L. and its anti-inflammatory effect on peripheral blood mononuclear cells (PBMCs) from healthy individuals. Using the MTT assay, we found that the methanolic or hexane extracts from any part of this herb did not cause toxicity, and cell viability percentage of PBMCs was found higher than 90% with regard to its concentration range from 0.19 to 100 µg/ml. However, the ethanolic extracts from flower (50 and 100 µg/ml), leaf (100 µg/ml) and whole plant (100 µg/ml) resulted in toxicity of PBMCs. As experimentally tested using an ELISA method, we also found that the methanolic extracts from leaf or whole plant, ethanolic extracts from whole plant and hexane extracts from trunk significantly reduced a level of pro-inflammatory cytokine (IL-6) (P <0.05) via inhibition of NF-B nuclear translocation as proven using immunocytochemistry and confocal microscope. Nonetheless, no change in the level of TNF-α was observed. In addition, the ethanolic extracts from whole plant significantly increased a level of anti-inflammatory cytokine (IL-10) (P <0.05). Therefore, the methanolic, ethanolic and hexane extracts of Vernonia cinerea L. possessed anti-inflammotory effect on human PBMCs.
