Structure determination of riboflavin by synchrotron high-resolution powder X-ray diffraction

The crystal structure of the stable form of vitamin B2 or riboflavin (C 17 H 20 N 4 O 6 ) was solved using high-resolution powder X-ray diffraction (PXRD). The high-resolution PXRD pattern of riboflavin was recorded at room temperature at the European Synchrotron Radiation Facility (Grenoble, France). The starting structural model was generated using a Monte Carlo simulated annealing method. The final structure was obtained through Rietveld refinement. The positions of the H atoms belonging to hydroxy groups were estimated from computational energy minimizations. The symmetry is orthorhombic with the space group P 2 1 2 1 2 1 and the following lattice parameters: a = 20.01308, b = 15.07337 and c = 5.31565 Å.