Inhibition of β-adrenergic binding by fungal metabolites

Strains of Aspergillus flavus, Fusarium sp., Rhizopus sp. and Candida albicans all produced inhibitors of beta-adrenergic receptor binding; strains of Saccharomyces sp. and Schizosaccharomyces sp. did not. In tests with glutamic acid as the sole nutrient source, a Fusarium sp. produced four-fold larger amounts of inhibitor than the other fungi. The inhibitor from the Fusarium sp. was further purified by lyophilisation and sequential solvent extraction in chloroform, ethyl acetate and butanol; 60% of the original activity was recovered. The inhibitor had an estimated molecular size of 650 Da, and did not absorb light in the visible or ultraviolet range. When compared with a similar inhibitor from Escherichia coli, the Fusarium sp. inhibitor appeared to be a more potent inhibitor of beta-adrenergic and dopaminergic binding to mammalian cells.