Phagocyte Immunomodulatory Activity of Oenothein B, A Macrocyclic Elligatannin Isolated from <i>Epilobium angustifolium</i>

Abstract

Epilobium angustifolium has been traditionally used to treat of a number of diseases; however, not much is known regarding its effect on innate immune cells. We found that extracts of E. angustifolium activated functional responses in neutrophils and monocyte/macrophages. Activity‐guided fractionation, followed by mass spectroscopy and NMR analysis, resulted in the identification of oenothein B as the primary component responsible for phagocyte activation. Oenothein B, a dimeric hydrolysable tannin, dose‐dependently induced a number of phagocyte functions in vitro , including intracellular Ca 2+ flux, production of reactive oxygen species (ROS), chemotaxis, nuclear factor (NF)‐κB activation, and proinflammatory cytokine production. Furthermore, oenothein B was active in vivo , inducing keratinocyte chemoattractant (KC) production and neutrophil recruitment to the peritoneum after intraperitoneal administration. The ability of oenothein B to modulate phagocyte functions in vitro and in vivo suggests that this compound is responsible for at least part of the therapeutic properties of E. angustifolium extracts. This work was supported in part by NIH grants RR‐020185 and RR‐016455 and NIH contract HHSN266200400009C.