Anziaic acid

DNA topoisomerases perform the essential function of maintaining DNA topology in prokaryotes. DNA gyrase, an essential enzyme that introduces negative supercoils, is a clinically validated target. However, topoisomerase I (Topo I), an enzyme responsible for DNA relaxation has received less attention as an antibacterial target, probably due to the ambiguity over its essentiality in many organisms. The Mycobacterium tuberculosis genome harbors a single topA gene with no obvious redundancy in its function suggesting an essential role. The topA gene could be inactivated only in the presence of a complementing copy of the gene in M. tuberculosis. Furthermore, down-regulation of topA in a genetically engineered strain of M. tuberculosis resulted in loss of bacterial viability which correlated with a concomitant depletion of intracellular Topo I levels. The topA knockdown strain of M. tuberculosis failed to establish infection in a murine model of TB and was cleared from lungs in two months post infection. Phenotypic screening of a Topo I overexpression strain led to the identification of an inhibitor, thereby providing chemical validation of this target. Thus, our work confirms the attractiveness of Topo I as an anti-mycobacterial target.

The aim of this study was to investigate antioxidant, antimicrobial and anticancerous activity of Melanelia subaurifera and Melanelia fuliginosa. The phytochemical analysis was determined by HPLC-UV method. Antioxidant activity was evaluated by DPPH and reducing power assay while antimicrobial activity was determined by minimal inhibitory concentration. The cytotoxic activity was tested using MTT method. The method for quantification of 2'-O-methyl anziaic acid and lecanoric acid in these lichens using RF-HPLC was also developed and validated. The depsides (lecanoric acid, gyrophoric acid, atranorin, anziaic acid and 2'-O-methyl anziaic acid), and dibenzofurane (usnic acid) were identified in these lichens. The antioxidant activity (IC50) of lichens extracts ranged from 121.52 to 424.51 μg/ml. 2'-O-Methyl anziaic acid showed the highest antimicrobial activity with MIC ranging from 0.0625 to 1 mg/ml. M. subaurifera extract showed the highest cytotoxic activity against the tested cell lines (IC50 = 9.88 to 31.64 μg/ml).

Naturally occurring anziaic acid was very recently reported as a topoisomerase I inhibitor with antibacterial activity. Herein total synthesis of anziaic acid and structural analogues is described and the preliminary structure-activity relationship (SAR) has been developed based on topoisomerase inhibition and whole cell antibacterial activity.