Naphthofluorescein (Naphthafluorescein) is a Mint3 inhibitor with potential antitumor and anti-inflammatory activities, inhibits the interaction between HIF-1 and Mint3, inhibits Mint3-dependent HIF-1 activity, and inhibits glycolytic activity in cancer cells and macrophages without showing significant in vitro cytotoxicity or in vivo side effects. Naphthofluorescein is also a fluorescent pH-sensitive probe for functional Cherenkov imaging.