Curcumin analogues and their hybrid molecules as multifunctional drugs.

Curcumin (diferuloylmethane or 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) is an interesting compound that is characterized by a special chemical structure with a diversified biological and pharmaceutical properties. A huge number of studies have explored the medicinal properties of curcumin, including antitumoral, antimicrobial, anti-inflammatory, antioxidant, antihepatotoxic, antihyperlipidemic, antiviral, and anti-Alzheimer's disease effects. Despite its range of reported pharmacological effects, it has poor bioavailability during oral administration and poor solubility and so, it is limited in its clinical applicability. Therefore, several strategies were developed to overcome this disadvantage, such as nanoparticle and formulations in liposomal, micellar or phospholipid complex. One of the most common strategies is the design and synthesis of new curcumin derivatives and analogues that have better therapeutic properties and bioavailability where great efforts have been made by scientists in this field. Thus, the scope of this review is to report the up-to-date synthesized derivatives, analogues and to classify them according to their chemical structure. The review sheds light on the most important and potent compounds where several effective moieties are introduced into different positions so as to be suitable for different biological activities. Additionally, an interesting class of curcumin hybrids and the synergy that would be expected based on their chemical structures are also covered in this review. Also, the structure-activity relationship of several analogues and some selected examples of patents on curcumin analogues were displayed.