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Ukrainian Food Journal
Introduction. The aim of this review is to focus on the unique chemistry of curcumin to explain i... more Introduction. The aim of this review is to focus on the unique chemistry of curcumin to explain its dissimilar behaviour in different mediums. Materials and methods. The papers regarding structure-activity relationship studies of curcumin as antioxidant or pro-oxidant were examined. This review summarizes the achievements made in this field since 1980. Results and discussion. Curcumin is the principal curcuminoid found in turmeric and is generally considered as the most active constituent of turmeric compared to other curcuminoids. Enormous research has been carried out to explain the beneficial activities of curcumin. It has been the centre of attraction for potential treatment of an array of diseases such as cancer, Alzheimer, diabetes, allergies, arthritis and other chronic illnesses. It also possesses antioxidant activity at lower concentration. In contrast, the pro-oxidant effect has also been reported. The behaviour of curcumin to act as antioxidant or pro-oxidant depends on its structural form. Curcumin exists in two tautomeric forms, keto and enol. In keto form, curcumin exerts antioxidant activity. The enol form is prone to degradation. Hence, it is essential to maintain curcumin in keto form. In polar and acidic medium, curcumin exists in keto form whereas in non-polar and basic medium, it undergoes degradation. The mechanisms of degradation of curcumin under different mediums are discussed. Under basic conditions, nucleophilic attack of hydroxyl group is involved and under non-polar conditions, free radical mechanism is involved. Degradation under basic conditions leads to complete breaking of the molecule while under non-polar conditions, it proceeds via peroxide intermediate formation, clarifying the pro-oxidant effect of curcumin. In either of the cases, vanillin is the degradation product besides other degradation products. The discussion is further extended for the other two curcuminoids, viz. demethoxycurcumin and bisdemethoxycurcumin as well. The antioxidant activity of curcumin is the highest whereas bisdemethoxycurcumin exhibits least antioxidant activity amongst curcuminoids. However, the rate of degradation of curcumin is also maximum amongst curcuminoids followed by demethoxycurcumin and bisdemethoxycurcumin. This reveals that the electron donating methoxy group influences the activity of curcuminoids. Thus, structure of a constituent is responsible for its activity. Conclusion. The importance of a particular medium to achieve the beneficial activities of curcumin is confirmed.
![Research paper thumbnail of A facile one pot synthesis of novel N1-(2-nitrophenyl sulphenyl substituted) pyrrolidino[2,1-c][1,4]-benzodiazepine, thiazolidino[3,2-c][1,4]-benzodiazepine and thiazolidino[4,3-c][1,4]-benzodiazepine from the corresponding N-substituted isatoic anhydride](https://a.academia-assets.com/images/blank-paper.jpg)
](Journal of the Indian Chemical Society, 2009
Ukrainian Food Journal
Introduction. The aim of this review is to focus on the unique chemistry of curcumin to explain i... more Introduction. The aim of this review is to focus on the unique chemistry of curcumin to explain its dissimilar behaviour in different mediums. Materials and methods. The papers regarding structure-activity relationship studies of curcumin as antioxidant or pro-oxidant were examined. This review summarizes the achievements made in this field since 1980. Results and discussion. Curcumin is the principal curcuminoid found in turmeric and is generally considered as the most active constituent of turmeric compared to other curcuminoids. Enormous research has been carried out to explain the beneficial activities of curcumin. It has been the centre of attraction for potential treatment of an array of diseases such as cancer, Alzheimer, diabetes, allergies, arthritis and other chronic illnesses. It also possesses antioxidant activity at lower concentration. In contrast, the pro-oxidant effect has also been reported. The behaviour of curcumin to act as antioxidant or pro-oxidant depends on its structural form. Curcumin exists in two tautomeric forms, keto and enol. In keto form, curcumin exerts antioxidant activity. The enol form is prone to degradation. Hence, it is essential to maintain curcumin in keto form. In polar and acidic medium, curcumin exists in keto form whereas in non-polar and basic medium, it undergoes degradation. The mechanisms of degradation of curcumin under different mediums are discussed. Under basic conditions, nucleophilic attack of hydroxyl group is involved and under non-polar conditions, free radical mechanism is involved. Degradation under basic conditions leads to complete breaking of the molecule while under non-polar conditions, it proceeds via peroxide intermediate formation, clarifying the pro-oxidant effect of curcumin. In either of the cases, vanillin is the degradation product besides other degradation products. The discussion is further extended for the other two curcuminoids, viz. demethoxycurcumin and bisdemethoxycurcumin as well. The antioxidant activity of curcumin is the highest whereas bisdemethoxycurcumin exhibits least antioxidant activity amongst curcuminoids. However, the rate of degradation of curcumin is also maximum amongst curcuminoids followed by demethoxycurcumin and bisdemethoxycurcumin. This reveals that the electron donating methoxy group influences the activity of curcuminoids. Thus, structure of a constituent is responsible for its activity. Conclusion. The importance of a particular medium to achieve the beneficial activities of curcumin is confirmed.
Journal of the Indian Chemical Society, 2009