Leoidin is a metabolite of the lichen, Lecanora gangleoides, first published in 1986 and recently reported as an inhibitor of protein synthesis in Pseudomonas aeruginosa. Leoidin is bacteriostatic, targeting PheRS. Leoidin is a weak inhibitor of human HPGC (15-hydroxyprostaglandin dehydrogenase) and of sodium fluorescein uptake in OATP1B1- or OATP1B3-transfected CHO cells.