Antialgal, antibacterial and antifungal activity of two metabolites produced and excreted by cyanobacteria during growth

SummaryThe antimicrobial activity of two cyanobacterial exometabolites, norharmane (9H-pyrido(3,4-b)indole) and 4,4′-dihydroxybiphenyl, was determined in suspension assays. Good anticyanobacterial activities (concentrations of 8–80 μg ml−1) and moderate antibacterial (16–160 μg ml−1) and antifungal (32–40 μg ml−1) activities were found for both compounds. The natural function as allelopathic chemicals and a possible applicability as antifouling agents or leads for the development of new antifouling chemicals are discussed.