Alkaloid chelirubine and DNA: blue and red luminescence.

Extracts from Himalayan herb Dicranostigma lactucoides containing alkaloid chelirubine have been used for centuries in Chinese herbal medicine. We have found a new utilization for the alkaloid: it can be used as a DNA fluorescent probe showing blue (free form) and red (intercalated to DNA) luminescence emission after irradiation by near-UV light. Besides quantification of DNA (LOD = 6 ng ml(-1)) it can also be used as a supravital cell probe because chelirubine molecules can effectively enter into the living cell through the cell membrane.