Three new structural forms of thiocolchicoside, a muscle relaxant, as shown by X-ray powder diffraction

Abstract

Thiocolchicoside (THC) is an important active pharmaceutical ingredient (API) used as a muscle relaxant because of its anti-inflammatory and analgesic effects. The only entry for a THC-related compound present in the Cambridge Structural Database (CSD) corresponds to a THC ethanol solvate hydrate (refcode: THCLCS). The diffraction pattern recorded for the THC raw material (C27H33NO10S·xH2O) is different from the pattern calculated using the THCLCS crystallographic data contained in the CSD. The indexing of the THC raw material pattern, produced an orthorhombic unit cell with a = 28.018(7) Å, b = 12.519(2) Å, c = 8.519(1) Å, and V = 2988.01 Å3. All the diffraction maxima of the powder pattern of a phase recrystallized in water (C27H33NO10S·2H2O) can be indexed in an orthorhombic cell with a = 25.264(4) Å, b = 13.537(3) Å, c = 8.553(1) Å, and V = 2925.12 Å3. Thermogravimetric analysis shows that this compound is a dihydrate phase. Upon heating, a new anhydrous phase (C27H33NO10S) with a monoclinic cell and unit cell parameters: a = 17.090(5) Å, b = 19.485(5) Å, c = 8.526(3) Å, β = 100.30(2)°, and V = 2793.34 Å3 is obtained.