(-)-Viriditoxin is a mycotoxin originally isolated from A. viridinutans that has antibacterial and antiproliferative activity. It is active against methicillin-sensitive and -resistant S. aureus (MSSA and MRSA, respectively), tetracycline-sensitive and -resistant Staphylococcus, vancomycin-sensitive and -resistant Enterococcus, and penicillin-sensitive and -resistant S. pneumoniae (MICs = 2-32 μg/ml). (-)-Viriditoxin is also active against fish pathogens, including S. iniae and S. parauberis (MICs = 0.16-0.21 μg/ml). It inhibits polymerization and the GTPase activity of E. coli FtsZ, a tubulin-like GTPase involved in bacterial cell division (IC50s = 8.2 and 7 μg/ml, respectively). (-)-Viriditoxin inhibits proliferation of human DU145, LNCaP, and PC3 prostate cancer cells (IC50s = 5.36, 0.63, and 7.6 μM, respectively) . It is also toxic to mice (LD50 = 2.8 mg/kg, i.p.).
Darinaparsin is a dimethylated arsenic linked to glutathione. It is cytotoxic to DU145, LNCaP, and PC3 prostate cancer cells (IC50s = 5-10 µM) and patient-derived primary prostate cancer cells (IC50s = 2.5-20 µM), as well as Jurkat T cell lymphoma and L540 Hodgkin lymphoma cells (IC50s = 2.7 and 1.3 µM, respectively). [1][2] It decreases the tumor-initiating subpopulation in DU145 and PC3 cells and halts the cell cycle in the G2/M phase. Darinaparsin decreases transcription of Gli-2, a transcription factor that mediates Sonic hedgehog signaling, when used at a concentration of 1.5 but not 3 µM. It decreases SHP1 phosphatase activity and increases ERK phosphorylation. [2] Darinaparsin reduces tumor growth in DU145 and PC3 prostate cancer mouse xenograft models when administered at a dose of 100 mg/kg every other day.[1]