Cercosporamide is a natural antifungal phytotoxin isolated from the Cercosporidium fungus, which infects the leaves of cassava plants. Its antifungal effect results from its selective and potent inhibition of fungal PKC-like 1 kinases (Pkc1), which are central to cell wall integrity (IC50 = 25 nM for Candida Pkc1). Cercosporamide less effectively inhibits human PKC isoforms PKCα, β, and γ (IC50s = 1.02, 0.35, and 5.8 μM, respectively), an action linked to lowering of plasma glucose in hyperglycemic mice. However, it potently inhibits MAPK-interacting kinases Mnk1 and Mnk2 (IC50 = 115 and 11 nM, respectively), reducing protein translation in cancer cells. Cercosporamide is orally bioavailable.
