Activities and prevalence of proteobacteria members colonizing Echinacea purpurea fully account for in vitro macrophage activation exhibited by extracts of this botanical

Authors: HARON, MONA - University Of Mississippi; TYLER, HEATHER - University Of Mississippi; PUGH, NIRMAL - University Of Mississippi; MORAES, RITA - University Of Mississippi; MADDOX, VICTOR - Mississippi State University; JACKSON, COLIN - University Of Mississippi; PASCO, DAVID - University Of Mississippi

Submitted to: Planta Medica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2016
Publication Date: 4/30/2016
Citation: Haron, M.H., Tyler, H.L., Pugh, N.D., Moraes, R.M., Maddox, V.L., Jackson, C.R., Pasco, D.S. 2016. Activities and prevalence of proteobacteria members colonizing Echinacea purpurea fully account for in vitro macrophage activation exhibited by extracts of this botanical. Planta Medica. 89(4-5):451-62. DOI: 10.1007/s11103-015-0381-3

Interpretive Summary: Echinacea purpurea is one of the most popular immune enhancing botanicals in the US herbal market and is used in the prevention and treatment of upper respiratory tract infections. A growing body of literature indicates that variation in the amount and type of bacteria colonizing E. purpurea is responsible for the differences in the immunostimulatory potential of Echinacea plant material. In the current study we determined the bacterial community composition within commercial and freshly harvested E. purpurea aerial samples. We obtained bacterial isolates representing different taxa that were identified to be present within E. purpurea and found that the activity exhibited by extracts of these isolates varied substantially. Members of the Proteobacteria exhibited the highest potency for in vitro macrophage activation and were the most predominant taxa. Furthermore, the mean activity exhibited by the Echinacea extracts could be fully accounted for solely by the activities and prevalence of Proteobacteria members comprising the plant community composition. The efficacy of E. purpurea material for use against respiratory infections may be determined by the Proteobacterial community composition of this plant since ingestion of bacteria (probiotics) is reported to have a protective effect against this health condition.

Technical Abstract: Evidence supports the theory that the bacterial communities colonizing E. purpurea contribute to the innate immune enhancing activity of this botanical. Previously we reported that only about half of the variation in in vitro monocyte stimulating activity exhibited by E. purpurea extracts could be accounted for by total bacterial load within the plant material. In the current study we test the hypothesis that the type of bacteria, in addition to bacterial load, is necessary to fully account for extract activity. Bacterial community composition within commercial and freshly harvested (wild and cultivated) E. purpurea aerial samples was determined using high-throughput 16S rRNA gene pyrosequencing. We acquired bacterial isolates representing 38 different taxa that were identified to be present within E. purpurea and found that the activity exhibited by extracts of these isolates varied by over 8,000-fold. Members of the Proteobacteria exhibited the highest potency for in vitro macrophage activation and were the most predominant taxa. Furthermore, the mean activity exhibited by the Echinacea extracts could be fully accounted for solely by the activities and prevalence of Proteobacteria members comprising the plant community composition. The efficacy of E. purpurea material for use against respiratory infections may be determined by the Proteobacterial community composition of this plant since ingestion of bacteria (probiotics) is reported to have a protective effect against this health condition.