Community Metabolic Interactions, Vitamin Production and Prebiotic Potential of Medicinal Herbs used for Immunomodulation

Accumulating studies emphasize the intimate relationship between the gut microbiota and host immune system and its activities. These interactions are largely unknown but involve secreted microbial products that activate or repress a variety of immune cell types. Historically, the health benefits of medicinal herbs have been viewed as an intrinsic quality of the herb itself. More recently, we and others have hypothesized that the health benefits of medicinal herbs may be partially due to the activities of the gut microbiota that metabolize herb constituents or biotransformation of herb encoded molecules and secondary metabolites. Here we evaluated the effect of immunomodulatory, medicinal Ayurvedic herbs on gut microbiota in vitro to assess their prebiotic potential. We extended these analyses further by employing genome reconstruction of short chain fatty acid biosynthetic pathways, vitamin biosynthesis, amino acid biosynthesis and catabolism, sugar utilization and glycosyl hydrolase representation in herb-selected cultures. All immunomodulatory herbs displayed substantial prebiotic potential that altered community diversity and composition, targeting unique taxonomic groups. Analysis of biosynthetic capacity of herb selected communities suggests that many of the 11 herbs tested altered the community metabolism due to differential glycan harvest and sugar utilization and secreted products with the potential to impact host physiology and immune function. Taken together, these results provide a useful framework to further evaluation of these immunomodulatory herbs in vivo to maintain immune homeostasis or achieve desired regulation of immune components in the context of disease.