Antimicrobial and Antifungal Activities of Quasi-Dimeric and Related Alkaloids

Abstract A series of quasi-dimeric indole alkaloids was tested for antimicrobial activity. Only three of the 34 compounds did not show activity against any of the test organisms (BACILLUS SUBTILIS, STAPHYLOCOCCUS AUREUS, MYCOBACTERIUM SMEGMATIS, ESCHERICHIA COLI, PSEUDOMONAS AERUGINOSA, CANDIDA ALBICANS, ASPERGILLUS NIGER). None of the compounds was active against P. AERUGINOSA, C. ALBICANS, and A. NIGER at the levels tested. Three alkaloids had activity against E. COLI. It was concluded that the stereochemistry of the C/D ring junction in the alkaloids is important for the activity. Aromatic substitution and oxidation of the C-ring of the quasi-dimeric alkaloid decreases the activity. Harman, dihydroharman, and a synthetic bisharman (34) were found to be inactive in this test system at the concentrations tested.