Abstract
Curcumin, the polyphenolic pigment from turmeric has excellent therapeutic potential but due to poor aqueous solubility and metabolic instability, it has not yet been possible to use it as a drug. Structural studies have revealed that depending upon ambient pH, curcumin can remain in keto- enol tautomeric forms. The keto form is generated at acidic pH and due to the presence of the β-diketone motif in the molecule, the methylene group gets activated and can donate a hydrogen atom to reactive oxygen species which is responsible for its anti-oxidative properties. The enol form of curcumin which is present at alkaline pH becomes a planar molecule due to extensive delocalization of electrons from one aromatic ring to the other through the pi orbital of C=C bonds in the heptadione linkage. At alkaline pH, curcumin gets degraded to smaller molecules which have interestingly been shown to have therapeutic activity. Molecular interaction studies have identified the methylene group in the β-diketone domain and the methoxy as well as the phenoxy group on the aromatic rings of curcumin molecule to be the contact points with enzymes and signaling molecules and may be involved in inactivating them. The bioavailable forms of curcumin cited in this review have been formulated using curcumin entrapped or bound to polymeric nanoparticles, liposomes, phospholipid complexes, nanoemulsions, or polymeric micelles and have been tested against chronic inflammatory conditions in animal models or cell lines.
Keywords
Nano Curcumin, Nanoparticles, Liposomes, Neurodegenerative Diseases