Open AccessPure Curcumin Spherulites from Impure Solutions via Nonclassical Crystallization
Author(s) -
K. Vasanth Kumar,
Kiran A. Ramisetty,
K. Renuka Devi,
G. Rama Krishna,
Claire Heffernan,
Andrew Stewart,
Jian Guo,
Srinivas Gadipelli,
Dan J. L. Brett,
Evangelos P. Favvas,
Åke C. Rasmuson
Publication year - 2021
Publication title -
acs omega
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.779
H-Index - 40
ISSN - 2470-1343
DOI - 10.1021/acsomega.1c02794
Subject(s) - supercooling , nucleation , crystallization , spherulite (polymer physics) , crystallite , materials science , impurity , particle (ecology) , crystallography , curcumin , nanometre , crystal (programming language) , chemical engineering , chemistry , thermodynamics , organic chemistry , composite material , metallurgy , engineering , biochemistry , physics , oceanography , computer science , programming language , geology
Crystallization experiments performed with highly supercooled solutions produced highly pure (>99 wt %) and highly crystalline mesocrystals of curcumin from impure solutions (∼22% of two structurally similar impurities) in one step. These mesocrystals exhibited a crystallographic hierarchy and were composed of perfectly or imperfectly aligned nanometer-thick crystallites. X-ray diffraction and spectroscopic analysis confirmed that the spherulites are a new solid form of curcumin. A theoretical hypothesis based on particle aggregation, double nucleation, and repeated secondary nucleation is proposed to explain the spherulite formation mechanism. The experimental results provide, for the first time, evidence for an organic molecule to naturally form spherulites without the presence of any stabilizing agents. Control experiments performed with highly supercooled pure solutions produced spherulites, confirming that the formation of spherulites is attributed to the high degree of supercooling and not due to the presence of impurities. Likewise, control experiments performed with a lower degree of supercooling produced impure crystals of curcumin via classical molecular addition mechanisms. Collectively, these experimental observations provide, for the first time, evidence for particle-mediated crystallization as an alternate and efficient method to purify organic compounds.