An ansamycin antibiotic and antifungal; inhibits bone resorption (IC50 = 21 nM) and pp60c-src kinase (IC50 = 50 nM); inhibits L-leucine incorporation during protein synthesis (IC50 = 58 nM); inhibits TNF-α-induced ICAM1 expression (IC50 = 300 nM); potentiates the action of chemotherapeutics; hydroquinone of ansatrienin A