4.11. Calothrixin A
Cell extracts of Calothrix isolates were found to be helpful in inhibiting the growth of human HeLa cancer cells in a dose-dependent manner. Calothrixin A and B, pentacyclic metabolites, are obtained from microalgae, which have growth inhibitory effects. More than 50% of the marine cyanobacteria are potentially exploitable for extracting bioactive substances that are effective in either killing the cancer cells by inducing apoptotic death or affecting the cell signaling through activation of the members of protein kinase-c family of signaling enzymes.