Impact of Affecting the Formation Defects in Vinpocetine Crystals

Combined with rigorous and accurate experimental protocols, the key influencing factors of the formation of macroscopic defects in vinpocetine (VIP) solution were studied with the aim to propose a universal strategy toward the inquiry of the formation mechanism of crystal defects in organic crystals. By screening solvents and polymorphism, it was determined that vinpocetine has two crystal habits (habits I & II); the content and formation mechanism of the defects in two crystal habits was confirmed to be disparate. The impacts of temperature, supersaturation, agitation, and ultrasound on the defects of the habit I were investigated in a targeted manner. The crystal surface indexation method was used to visually analyze the growth behavior of VIP single crystals. It was revealed that the stepwise lowered layers of {(100)} crystal planes in crystal habit I were primary factors inducing negative defects formation. In addition, the molecular dynamics simulation was employed to investigate the interactions between the surface of vinpocetine crystal and the pure solvent. The growth rate and surface roughness of the crystal faces were simulated using the modified attachment energy model. Through the discussion of surface structure and adsorption mechanism, it was expounded that the crystal growth kinetics induced the formation of depressions and further contributes to the formation of defects in cavities and fine inclusions.