Tetrahydrobiopterin (THB) was discovered by Seymour Kaufman,playing a role as an enzymatic cofactor . The first enzyme found to use THB is phenylalanine hydroxylase (PAH) .

The Tetrahydrobiopterin, with the CAS registry number 17528-72-2, is also known as 2-Amino-6-(1,2-dihydroxypropyl)-5,6,7,8-tetrahydro-4(1H)-pteridinon. This chemical's molecular formula is C₉H₁₅N₅O₃ and molecular weight is 241.25. What's more, its IUPAC name is called 2-Amino-6-(1,2-dihydroxypropyl)-5,6,7,8-tetrahydro-1H-pteridin-4-one. It is a naturally occurring essential cofactor of the three aromatic amino acid hydroxylase enzymes, used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin (5-hydroxytryptamine, 5-HT), melatonin, dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), and is a cofactor for the production of nitric oxide (NO) by the nitric oxide synthases. The production is biosynthesized from guanosine triphosphate by three chemical reactions, those of which are mediated by the enzymes, 6-pyruvoyltetrahydropterin synthase, and sepiapterin reductase.

Physical properties about Tetrahydrobiopterin are: (1)ACD/LogP: -4.22; (2)# of Rule of 5 Violations: 1; (3)ACD/LogD (pH 5.5): -6.11; (4)ACD/LogD (pH 7.4): -4.94; (5)ACD/BCF (pH 5.5): 1; (6)ACD/BCF (pH 7.4): 1; (7)ACD/KOC (pH 5.5): 1; (8)ACD/KOC (pH 7.4): 1; (9)#H bond acceptors: 8; (10)#H bond donors: 7; (11)#Freely Rotating Bonds: 4; (12)Polar Surface Area: 60.85 Å²; (13)Index of Refraction: 1.821; (14)Molar Refractivity: 55.42 cm³; (15)Molar Volume: 127.1 cm³; (16)Surface Tension: 86.7 dyne/cm; (17)Density: 1.89 g/cm³; (18)Flash Point: 260.2 °C; (19)Enthalpy of Vaporization: 89.4 kJ/mol; (20)Boiling Point: 506.6 °C at 760 mmHg; (21)Vapour Pressure: 2.2E-12 mmHg at 25 °C.

You can still convert the following datas into molecular structure:
(1) SMILES: O=C2\N=C(/NC=1NCC(NC=12)C(O)C(O)C)N
(2) InChI: InChI=1S/C9H15N5O3/c1-3(15)6(16)4-2-11-7-5(12-4)8(17)14-9(10)13-7/h3-4,6,12,15-16H,2H2,1H3,(H4,10,11,13,14,17)
(3) InChIKey: FNKQXYHWGSIFBK-UHFFFAOYSA-N

The toxicity data is as follows: