Phenolic compounds have been very well known for their antioxidant properties, owing to their unique ability to act as free radical scavengers which, in turn, is an outstanding attribute of their unique biochemical structure. Recent accumulating lines of evidence inculcate sustainable interest and curiosity towards the chemoprotective nature of the natural polyphenolic compound curcumin (diferuloylmethane) against oxidative stress-mediated disorders. Curcumin is naturally found as a constituent of dietary spices called turmeric, extracted from the plant Curcuma longa. However, like every phenolic antioxidant, curcumin possesses a concentration and medium dependent anti- and pro-oxidant behaviour. A detailed study of the structure-function analysis and the understanding of the mode of action of curcumin as well as its chemical analogues is thus essential to understand the selective biochemical consequences of curcumin. Moreover, the presence of transition metal ions, route of administration, and localized tissue are also the vital decisive factors to determine curcumin behaviour. With this viewpoint, this paper sheds lights on the medium dependent prooxidative and antioxidative attributes of curcumin. Further, with respect to emergence of nanocarriers, a brief discussion focusing on the biochemical effect exertion of curcumin chiefly due to targeted and slow release has also been added towards the end. 1. Introduction Phenolic compounds are widely accepted and recommended for their antioxidant activities [1–3].The chemical structure of the phenolic compounds imparts them the ability to serve as free radical scavengers. A phenolic compound consists of a benzene ring and an alcoholic hydroxyl group, which are the defining features of its acidic nature. The type of the compound to be reduced, the degree of methoxylation, and the number of the hydroxyl groups present are some of the vital parameters that determine the antioxidant activity of a phenolic antioxidant. A diligent look into the structure of typical alcohol and a phenol leads to the conclusive finding that, in alcohols, the –OH group is bonded to saturated carbon atom while, in case of phenols, the hydroxyl (–OH) group is bonded to an unsaturated carbon atoms and this is clearly an indication that release of hydrogen ion is easier from the phenols than from the corresponding alcohols. That’s why phenols are widely known by the name carbolic acid. Furthermore, pKa value for phenols is also more than that of the typical alcohols, which makes phenol a stronger acid than the alcohols [4]. A phenolic
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