M.N.A. Rao

Oxygen radical scavenging activity of curcumin

Abstract Curcumin, a potent anti-inflammatory agent, has been studied for its ability to scavenge reactive oxygen radicals which are implicated in inflammation. Studies showed that it is a good scavenger of hydroxyl radical at high concentrations but at low concentrations activated the Fenton system to generate an increased amount of hydroxyl radical. Curcumin was also studied for Superoxide scavenging activity and was found to be a potent scavenger.

Nitric oxide scavenging by curcuminoids.

Because curcumin, a compound with anti‐inflammatory and anticancer activity, inhibits induction of nitric oxide synthase in activated macrophages and has been shown to be a potent scavenger of free radicals we have investigated whether it can scavenge nitric oxide directly.

Curcuminoids as potent inhibitors of lipid peroxidation.

Abstract— Earlier studies showed that curcumin is a potent inhibitor of iron‐catalysed lipid peroxidation. Demethoxycurcumin, bisdemethoxycurcumin and acetylcurcumin were tested for their ability to inhibit iron‐stimulated lipid peroxidation in rat brain homogenate and rat liver microsomes. Comparison of the results with curcumin showed that all compounds are equally active, and more potent than α‐tocopherol. These results showed that the methoxy and phenolic groups contribute little to the activity. Spectral studies showed that all compounds could interact with iron. Thus, the inhibition of iron‐catalysed lipid peroxidation by curcuminoids may involve chelation of iron.

Curcumin inhibits nitrogen dioxide induced oxidation of hemoglobin

Curcumin protects hemoglobin from nitrogen dioxide induced oxidation. Curcumin was also found to scavenge nitrogen dioxide in a concentration dependent way. The study also explains the ability of curcumin to protect hemoglobin from nitrite induced oxidation, where nitrogen dioxide is a key intermediate.

Effect of curcumin on hydroxyl radical generation through Fenton reaction

Abstract The effect of curcumin on the production of hydroxyl radicals through the Fenton reaction has been studied. This study shows that curcumin can reduce ferric ion to ferrous and this ferrous ion can generate a hydroxyl radical in the presence of hydrogen peroxide through the Fenton reaction.

A newly synthetic chromium complex - chromium(phenylalanine)3 improves insulin responsiveness and reduces whole body glucose tolerance

Low‐molecular‐weight organic chromium complexes such as chromium picolinate are often used as dietary supplements to improve insulin sensitivity and to correct dyslipidemia. However, toxicity associated with such chromium compounds has compromised their therapeutic value. The aim of this study was to evaluate the impact of a newly synthesized complex of chromium with phenylalanine, Cr(pa)3 on insulin‐signaling and glucose tolerance. Cr(pa)3 was synthesized by chelating chromium(III) with d‐phenylalanine ligand in aqueous solution. In mouse 3T3‐adipocytes, Cr(pa)3 augmented insulin‐stimulated glucose‐uptake as assessed by a radioactive‐glucose uptake assay. At the molecular level, Cr(pa)3 enhanced insulin‐stimulated phosphorylation of Akt in a time‐ and concentration‐dependent manner without altering the phosphorylation of insulin receptor. Oral treatment with Cr(pa)3 (150 μg/kg/d, for six weeks) in ob/ob(+/+) obese mice significantly alleviated glucose tolerance compared with untreated obese mice. Unlike chromium picolinate, Cr(pa)3 does not cleave DNA under physiological reducing conditions. Collectively, these data suggest that Cr(pa)3 may represent a novel, less‐toxic chromium supplement with potential therapeutic value to improve insulin sensitivity and glycemic control in type II diabetes.

Inhibition of radiation-induced lipid peroxidation by curcumin

Abstract The ability of curcumin, a natural antioxidant from turmeric, to inhibit radiation-induced lipid peroxidation in rat liver microsomes was examined. Curcumin was incorporated into microsomes during ultracentrifugation. The antioxidant has significant time- and concentration-dependent inhibitory effect on lipid peroxidation induced by r-radiation. Inhibition of lipid peroxidation was also observed in microsomes samples previously saturated with N 2 O. Curcumin also inhibited lipid peroxidation during the post-irradiation incubation.

Antioxidant properties of dehydrozingerone and curcumin in rat brain homogenates.

The present study investigates the inhibition of lipid peroxidation by dehydrozingerone and curcumin in rat brain homogenates. Both the test compounds inhibited the formation of conjugated dienes and spontaneous lipid peroxidation. These compounds also inhibited lipid peroxidation induced by ferrous ions, ferric-ascorbate and ferric-ADP-ascorbate. In all these cases, curcumin was more active than dehydrozingerone and dl-α-tocopherol.

Curcumin inhibits iron-dependent lipid peroxidation

Abstract Curcumin inhibited lipid peroxidation induced by ferric ions, ferrous ions and ferric-ADP chelate (in the presence of ascorbic acid or NADPH) in rat brain homogenate and liver microsomes. This may represent one of the mechanisms through which curcumin exhibits anti-inflammatory and anticancer activities.

Curcumin inhibits nitrite-induced methemoglobin formation

Curcumin protects hemoglobin from nitrite‐induced oxidation to methemoglobin. The protection is not observed when curcumin is added after the autocatalytic stage of the oxidation of hemoglobin by nitrite. The ability of curcumin to scavenge superoxide may be responsible since superoxide is implicated in promoting the autocatalytic stage of oxidation of hemoglobin by nitrite.