Curcumin, a Biological Wonder Molecule: A Crystal Engineering Point of View

Abstract

Curcumin is a principal active ingredient of turmeric, extracted from the Curcuma longa plant. The presence of several curcuminoids (e.g., curcumin, demethoxycurcumin, bisdemethoxycurcumin, and cyclocurcumin) with extended π−π conjugation makes the Indian spice turmeric a bright yellow color. Curcumin can modulate various cellular targets and exhibits preventive and clinical efficacy against a wide variety of diseases such as inflammatory, proliferative, and angiogenic diseases, Alzheimer's disease, malaria, cancer, HIV, etc. Curcumin has been widely exploited by several branches of research scientists to study the chemistry behind its biological and chemical significance. However, application of curcumin is limited as medicine due to its poor aqueous solubility and bioavailability. While there are recent reports on curcumin on solubility/bioavailability improvement using excipients/additives, there has been little discussion from the viewpoint of crystal engineering. There is a need for understanding of the solid phases of curcumin to tailor physicochemical properties as they are alternative preformulations with prominent applications in pharma. Hence, in this review, we will focus on several crystalline solid forms such as polymorphs, cocrystals, eutectics, and noncrystalline solid forms like amorphous phases and coamorphous solid forms of curcumin reported in the literature/patent to date. In addition, we will briefly discuss metal complexes of curcumin and their application in drug development in combating modern lifestyle related diseases like cancer, Alzheimer's, etc.

Non-Curcuminoids from Turmeric and Their Potential in Cancer Therapy and Anticancer Drug Delivery Formulations

“…Indeed, an in-depth knowledge of curcumin-free compounds through these clinical trials help to understand that non-curcuminoids are powerful compounds that have the capability of treating various diseases and can even be more beneficial if impregnated in various formulations revolving liposomes, emulsions, solid lipid nanoparticles, and so on. Large-scale trials should be conducted to prove the potency of non-curcuminoid drug delivery formulations, which might be beneficial to assimilate an approval for human use [120].…”

High Amplification of the Antiviral Activity of Curcumin through Transformation into Carbon Quantum Dots

“…On the other hand, the X‐ray diffraction (XRD) patterns of Cur‐CQDs show a typical (002) broadband at 2θ = 26.5° corresponding to graphitic interlayer spacing of 0.33 nm (Figure S2, Supporting Information) . The pure curcumin exhibited many sharp XRD peaks in the range of 10°–30°, which implied high crystal polymorphism in the solid state caused by hydrogen bonding and π–π stacking interactions between curcumin molecules (Figure S2A, Supporting Information) . The two phenolic groups at the two ends of each curcumin molecule and the keto and enols are the centers of hydrogen bonding .…”

“…[27,28] The pure curcumin exhibited many sharp XRD peaks in the range of 10°-30°, which implied high crystal polymorphism in the solid state caused by hydrogen bonding and π-π stacking interactions between curcumin molecules ( Figure S2A, Supporting Information). [30,31] The two phenolic groups at the two ends of each curcumin molecule and the keto and enols are the centers of hydrogen bonding. [30] The intermolecular hydrogen bonding among the curcumin molecules gives rise to different conformations in the crystals, including linear, planar, curved, and twisted.…”

Additive‐Induced Selective Crystallization of the Elusive Form‐II of γ‐Aminobutyric Acid

“…First, the effect of additives on the solubility of GABA in aqueous solution was examined. This is because the introduction of additives can change the solubility of the solute and thereby affects the supersaturation degree of the system, which in turn may alter the pathway of nucleation and lead to the emergence of a new polymorph , . Fig.…”