The use of natural products in colorectal cancer drug discovery

Natural products (NPs) are evolutionarily designed and contain more complex and challenging structures than synthetic compounds. Since the 1980s, the pharmaceutical industry has gradually shifted to a strategy of developing targeted agents by screening libraries of synthetic compounds. However, NPs have recently received renewed focus as a rich repository for drug discovery. Irinotecan was developed as a derivative of camptothecin and was applied in standard regimens for metastatic colorectal cancer (CRC) worldwide. Additionally, polysaccharide K is approved for CRC in Japan and Taiwan in combination with cytotoxic agents. However, after the approval of irinotecan in 1996, no anti-cancer agents derived from NPs have been approved for CRC.This review discusses NPs that are currently under investigation for the treatment of CRC. In addition, other NPs derived as purified ingredients and crude extracts are listed and also discussed.The use of NPs for the discovery of anti-cancer agents has not been fully investigated. New technologies that are currently applied for synthetic compounds may be utilized for anti-cancer drug discovery including NPs for CRC.