Lupulon—An Antibiotic Extracted from the Strobiles of Humulus lupulus . * †

Summary and Conclusions

Lupulon, an antibiotic extracted from hop resins, was found to be effective against Gram-positive bacteria in vitro but inactive against Gram-negative organisms. The antibiotic had no demonstrable effect on a numlber of pathogenic and nonpathogenic molds and actinomycetes.

Lupulon displayed no activity in the presence of horse serum. In the absence of serum the antibiotic exhibited its greatest activity against M. tuberculosis H37Rv. This may have, been due to the fact that the tubercle bacillus was cultivated in a mineral medium with only an appreciable amount of interfering organic matter whereas the other organisms were grown, in a medium containing peptone. The addition of serum to both media completely inactivated the antibiotic.

Lupulon is slowly inactivated in the presence of air and more rapidly in the presence of serum. Because of its inactivation by serum, the antibiotic is not suitable for clinical administration.