Calphostin C is a natural chemical compound. It is one of the calphostins, isolated from the fungus Cladosporium cladosporioides. Calphostin C is a potent inhibitor of protein kinase C (PKC). Calphostin C is a natural chemical compound. It is one of the calphostins, isolated from the fungus Cladosporium cladosporioides. Calphostin C is a potent inhibitor of protein kinase C (PKC). Media related to Calphostins at Wikimedia Commons