An Investigation into the Immunomodulatory Activities of Sutherlandia frutescens in Healthy Mice

Sutherlandia frutescens is a medicinal plant that has been traditionally used in southern Africa for cancers, infections, and inflammatory conditions. We recently published experiments demonstrating that an aqueous extract of S . frutescens possessed potent immune-stimulatory activity. This work was carried out with murine macrophages, an immune cell type that plays a pivotal role in host defense from infection and in shaping host inflammatory and immune responses. Here, we conducted a series of follow-up experiments to explore the impact of consuming S . frutescens on host response to bacterial challenge using healthy mice. We found that feeding mice a diet containing S . frutescens failed to significantly alter host response to systemic infection by either a gram-positive or gram-negative bacterium (i.e., L . monocytogenes and E . coli , respectively). In contrast to the in vitro observations, we found no evidence that S . frutescens consumption stimulated in vivo inflammatory responses; instead, consumption of S . frutescens tended to diminish in vivo inflammatory responses. Several possible reasons for this are discussed.