Isodiospyrin is a novel human DNA topoisomerase I inhibitor, it exhibits cytotoxic activity to tumor cell lines. Isodiospyrin has antibacterial activity, the minimum inhibitory concentrations (MICs) against Gram-positive bacteria ranged from 0.78 to 50 microg/mL; it shows high antifungal activity against P. obscurans at 30uM with 81.4% growth inhibition, and moderate activity against P. viticola (36.6%).