Isodiospyrin, a natural dimeric naphthoquinone, is a human DNA topoisomerase I ( Topoisomerase ) inhibitor. Isodiospyrin can prevent both DNA relaxation and kinase activities of human topoisomerase I. Isodiospyrin shows anticancer, antibacterial and antifungal activities In Vitro Isodiospyrin (10-40 μM) does not induce human topoisomerase I (htopo I)-DNA covalent complexes. However, Isodiospyrin antagonizes Camptothecin-induced, htopo I-mediated DNA cleavage. Isodiospyrin binds htopo I but not DNA. Isodiospyrin exhibits strong inhibitory effect on the kinase activity of htopo I toward splicing factor 2/alternate splicing factor in the absence of DNA. Isodiospyrin against Gram-positive bacteria with MICs ranged from 0.78 to 50 μg/mL. While Isodiospyrin against Pseudomonas aeruginosa ATCC 15443 and S. typhi ranged from 50 to 100 μg/mL. The MIC for M. chelonae is between 6.25 and 25 μg/mL. Isodiospyrin (30 μM; 120-144 hours) shows 81.4 % growth inhibition of P. obscurans . The antifungal activity of Isodiospyrin at 30 μM against P. viticola is 57.7 %. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:Topoisomerase I