1-Ethyl indigo is a potent anticancer agent that inhibits the production of viruses and cancer cells. It is a chlorinated derivative of indole; in the presence of piperazine and cyanuric chloride, this compound binds to DNA, forming an adduct that interferes with replication. It has been shown to be highly effective in electron microscopy and as a photochemical intermediate in the synthesis of cortisone. Due to its fluorescent properties, it is also used as a fluorescent label in molecular biology research.
