X-Ray Absolute Structure of Nicergoline (Form I). Quantitative Analysis of Nicergoline Phase Mixture: Form I/Form II
The structure of semisynthetic ergot derivative nicergoline (form I ) was determined from X-ray single crystal diffraction data. The title alkaloid (10α-methoxy-1,6-dimethylergoline-8β-methanol-5'-bromonicotinate, C 24 H 26 BrN 3 O 3 ) crystallizes in the triclinic space group P1 , with a = 7.729(7), b = 8.695(4), c = 17.030(8) A, α = 100.90(4), β = 98.67(5), γ = 93.04(5)°, Z = 2. A structural comparison of nicergoline forms I and II was made. The quantitative analyses of some model phase mixtures form I / form II were carried out using both Rietveld full profile fitting method and linear regression of the peak intensity concentration dependence. Results obtained are in good mutual agreement. The smallest limit of detection of form II in binary mixture with form I is about 3% as found from powder diffraction study.