Curcumin, a pigment from turmeric, is one of the very few promising natural products that has been extensively investigated by researchers from both the biological and chemical point of view. While there are several reviews on the biological and pharmacological effects of curcumin, chemistry reviews are comparatively scarcer. In this article, an overview of different aspects of the unique chemistry research on curcumin will be discussed. These include methods for the extraction from turmeric, laboratory synthesis methods, chemical and photochemical degradation and the chemistry behind its metabolism. Additionally other chemical reactions that have biological relevance like nucleophilic addition reactions, and metal chelation will be discussed. Recent advances in the preparation of new curcumin nanoconjugates with metal and metal oxide nanoparticles will also be mentioned. Directions for future investigations to be undertaken in the chemistry of curcumin have also been suggested.

Curcumin, a polyphenolic natural product, exhibits therapeutic activity against a number of diseases, attributed mainly to its chemical structure and unique physical, chemical, and biological properties. It is a diferuloyl methane molecule [1,7-bis (4-hydroxy-3- methoxyphenyl)-1,6-heptadiene-3,5-dione)] containing two ferulic acid residues joined by a methylene bridge. It has three important functionalities: an aromatic o-methoxy phenolic group, α, β-unsaturated β-diketo moiety and a seven carbon linker. Extensive research in the last two decades has provided evidence for the role of these different functional groups in its crucial biological activities. A few highlights of chemical structural features associated with the biological activity of curcumin are: The o-methoxyphenol group and methylenic hydrogen are responsible for the antioxidant activity of curcumin, and curcumin donates an electron/ hydrogen atom to reactive oxygen species. Curcumin interacts with a number of biomolecules through non-covalent and covalent binding. The hydrogen bonding and hydrophobicity of curcumin, arising from the aromatic and tautomeric structures along with the flexibility of the linker group are responsible for the non-covalent interactions. The α, β-unsaturated β-diketone moiety covalently interacts with protein thiols, through Michael reaction. The β-diketo group forms chelates with transition metals, there by reducing the metal induced toxicity and some of the metal complexes exhibit improved antioxidant activity as enzyme mimics. New analogues with improved activity are being developed with modifications on specific functional groups of curcumin. The physico-chemical and structural features associated with some of the biological activities of curcumin and important analogues are summarized in this article.

The past two decades of this century have faced half a dozen pandemics caused by different kinds of viruses, affecting millions of people globally. Among them three zoonotic viruses of the beta-coronavirus family, namely SARS-CoV-1, MERS-CoV and SARS-CoV-2, have emerged in a span of 17 years. Prevention of viral infection using vaccines is the foremost strategy to combat viral infection, but development of a vaccine for a virus remains a challenging task due to high genetic diversity and high mutation rates. Treatment of viral disease at different stages by antiviral drugs is another strategy. Several antiviral agents, primarily aiming to disrupt the viral life cycle, have been developed. Extensive research in different labs across the globe has shown that selenium deficiency has been associated with pathogenicity of several viruses like influenza viruses, HIV, HBV, HSV-1, etc. While dietary selenium supplementation has been practiced clinically, researchers are now focusing on developing new synthetic organoselenium compounds as novel antiviral agents. In this essay we have covered different classes of selenium compounds, viz. N-heterocyclic selenium derivatives, ebselen and its derivatives, organoselenium compounds, and selenium nanoparticles, which have been evaluated for effective management of viral infections.

Diselenonicotinamide (DSNA), a synthetic organoselenium compound, was evaluated for its radioprotective effect in cellular models. A clonogenic assay