Pyrindolol is a bacterial metabolite that has been found in S. alboverticillatus.1 It inhibits neutral β-galactosidase by 50% under acidic, but not neutral, conditions when used at a concentration of 2 µg/ml. It is selective for β-galactosidase isolated from bovine liver over β-galactosidases isolated from human, bovine, pig, and rat tissues and sialidases isolated from C. perfringens, Streptomyces, and the H3N2 strain of influenza virus (IC50s = >250 µg/ml for all).1,2
1.Aoyagi, T., Kumagai, M., Hazato, T., et al.Pyridindolol, a new β-galactosidase inhibitor produced by actinomycetesJ. Antibiot. (Tokyo)28(7)555-557(1975) 2.Kumagai, M., Aoyagi, T., and Umezawa, H.Inhibitory activity of pyridindolol on β-galactosidaseJ. Antibiot. (Tokyo)29(7)696-703(1976)