The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings have not been peer reviewed and were not evaluated in accordance with the levels of evidence criteria established by NTP in March 2009. The findings and conclusions for this study should not be construed to represent the views of the NTP or the U.S. Government.
Echinacea is one of the herbal medicines, which has been purported to have a stimulatory effect on the immune system. ECH grows wild in the middle and eastern United States and is cultivated in Europe. It has been used for hundreds of years as medicine by American Indians. The medicinal parts include the root, leaves, and the whole plant. Multiple components of the plant are believed to contribute to the pharmacological activity of the herb. Among these are water-soluble immunostimulating polysaccharides (4-O-methylglucuronylarabinoxylans, acidic arabinorhamno-galactans), volatile oils, flavonoids such as rutin, caffeic and ferulic acid derivatives and alkamides. Preparations of echinacea have been reported to accelerate the healing of wounds. Additionally, echinacea has been reported to produce immune effects including increasing the number of white blood cells and spleen cells, and the production of various cytokines including IL-1, IL-6, and TNF-α.
Echinacea purpurea was nominated to the NTP for toxicological evaluation and was selected for immunotoxicity studies by the project officer. The purpose of these studies is to determine the potential effects of ECH on the immune system and the doses to be used in a full immunotoxicology protocol.
The study reported here is an immunotoxicological study conducted in female B6C3F1 mice, treated daily for 28 days by oral gavage. The in-life phase of the study was conducted between 19 Jan 01 and 05 Apr 01. ECH was prepared weekly as a suspension in the vehicle 0.5% methylcellulose.
In this study, in which ECH was administered orally at 30, 100, 300, 600, and 1000 mg/kg/day for 28 days, there were no effects on body weight. There were statistically significant increases for in body weight gain on Day 22-Day 1 of 50% for the 600 mg/kg dose level and a 31% and 35% increase for Day 29-Day 1 for the 600 and 1000 mg/kg dose levels. There were no notable changes among the standard toxicological parameters including organ weights or hematological parameters that were assessed.
Minimal immunotoxicological effects were observed in mice treated with ECH. ECH did not significantly affect either innate immunity or humoral immunity. However, the responses of the animals treated with ECH tended to be higher, albeit not statistically significant, in the humoral response assays. Furthermore, cell-mediated proliferative responses were enhanced.
In conclusion, with the exception of a slight increase in body weight gain, treatment with ECH had minimum effects on standard toxicological parameters. Overall, no statistically significant effects were observed on splenic phenotypes, humoral immune responses, or innate immune responses as evaluated by Natural Killer cell activity. Increased responses were observed in two proliferative assays, the multiple linear regression and the anti-CD3 mediated proliferation assay. In both cases a significant increasing trend was observed.