AMBIGOL A AND B - NEW BIOLOGICALLY-ACTIVE POLYCHLORINATED AROMATIC-COMPOUNDS FROM THE TERRESTRIAL BLUE-GREEN-ALGA FISCHERELLA-AMBIGUA

The isolation and structural elucidation of two novel highly halogenated aromatic compounds, ambigol A (1), 3-(2,4-dichlorophenoxy)-3',4,5',6-tetrachloro-2,2'-biphenyldiol, and ambigol B (2), 2,6-bis(2,4-dichlorophenoxy)-3,5-dichlorophenol, from a strain of the terrestrial cyanophyte Fischerella ambigua (Nag.) Gomont are described. The structures were established by spectroscopic methods, including the high temperature high resolution 2D-NMR INADEQUATE experiment, and confirmed, for ambigol A, by single-crystal X-ray crystallography. The biological activities of ambigol A and B were determined as antibacterial, antifungal, and molluscicidal. Ambigol A was demonstrated to inhibit the enzymes cyclooxygenase and HIV reverse transcriptase. The indole alkaloid tjipanazole D (3), previously isolated from the blue-green alga Tolypothrix tjipanasensis, was also obtained from this cyanobacterium. Tjipanazole D showed no significant biological activities.