. "Biopterin"@en . . . . . . . . . . . . . . . . . . . . . . . . . . . . . "A natural product that has been considered as a growth factor for some insects. [PubChem]"@en . . . . . . "Hayashi Uchino, Masaaki Azuma, Takehisa Ohashi, Kiyoshi Watanabe, \"Sulfate of 5,6,7,8-tetrahydro-L-erythro-biopterin and process for preparing the same.\" U.S. Patent US4649197, issued November, 1952."@en . . "experimental"@en .