In Vitro Macrophage Activation Exhibited by Echinacea Purpurea Aerial Extracts is Equivalent to the Total Activity Exhibited by the Endophytic Bacteria Associated with These Plant Samples

A growing body of evidence suggests that endophytic bacteria within Echinacea are the main source of components responsible for enhancing innate immune function in vitro and in vivo. We have found that 97% of in vitro monocyte/macrophage activation by extracts of Echinacea and other immune enhancing botanicals is due to the bacterial components LPS and Braun type lipoproteins. Furthermore, we have found that variations in total bacterial load within Echinacea samples were highly correlated with their in vitro immune enhancing activity and content of LPS. In this study we determined the total load and community composition of the bacterial endophytes associated with aerial material of commercial and freshly harvested (wild and locally cultivated) E. purpurea plants. Over 150 endophytic bacterial isolates were cultured from fresh Echinacea samples. Extracts from these isolates varied substantially in their ability to activate macrophages in vitro. The activity of each plant extract was then compared to the sum of the activities calculated from the amount of each bacterial taxa contained in the extracted plant material. Our results indicate that the type and amount of the endophytic bacteria identified in E. purpurea aerial material accounts for 87% and 100% of the activity exhibited by the freshly harvested and commercial plant extracts, respectively.