Antioxidant properties of novel curcumin analogues: A combined experimental and computational study

Synthesis, spectroscopic analysis, DFT, docking, MD and antioxidant activity of tetrahydrocurcumin

In recent years, numerous researchers have made local chemical modifications to the structure of curcumin while its basic structure remains unchanged, thus, producing curcumin derivatives. In this article, tetrahydrocurcumin was obtained by hydrogenation of curcumin, DFT calculation and characterization at the theoretical level of B3LYP/6 -311++G(d,p) were carried out. The observed IR and Raman spectra are in good agreement with the theoretical spectra. The FMO and ESP of tetrahydrocurcumin are predicted. The interaction in the system is shown graphically and analyzed by IGMH. Compared with curcumin, tetrahydrocurcumin lacks the unsaturated C = C bond, which makes it more stable and more bioavailable. Molecular docking with antioxidant targets elucidated the ligand-protein interaction and molecular dynamics simulation showed the antioxidant activity of tetrahydrocurcumin. The antioxidant activity of tetrahydrocurcumin was proved by DPPH• and •OH radical scavenging experiments. In essence, these derivatives exhibit enhanced physiological activity in certain aspects compared to the original curcumin. Moreover, the computational pharmacology techniques lay a theoretical groundwork for the development and modification of high-efficiency, low-toxicity drugs that interface with various targets of curcumin in the future.Communicated by Ramaswamy H. Sarma.

Inhibitory Effect of Curcumin-Inspired Derivatives on Tyrosinase Activity and Melanogenesis

Tyrosinase is a well-known copper-containing metalloenzyme typically involved in the synthesis of melanin. Recently, curcumin and several synthetic derivatives have been recognized as tyrosinase inhibitors with interesting anti-melanogenic therapeutic activity. In this study, three curcumin-inspired compounds 1, 6 and 7 were prepared in yields ranging from 60 to 88 % and spectrophotometric, electrochemical, in vitro and in silico analyses were carried out. The viability of PC12 cells, a rat pheochromocytoma derived-cell line, with compounds 1, 6 and 7, showed values around 80% at 5 µM concentration. In cell proliferation assays, compounds 1, 6 and 7 did not show significant toxicity on fibroblasts nor melanoma cells up to 10 µM with viability values over 90%. The inhibition of tyrosinase activity was evaluated both by a UV-Vis spectroscopic method at two different concentrations, 0.2 and 2.0 µM, and by amperometric assay with IC₅₀ for compounds 1, 6 and 7 ranging from 11 to 24 nM. Melanin content assays on human melanoma cells were performed to test the capability of compounds to inhibit melanin biosynthesis. All compounds exerted a decrease in melanin content, with compound 7 being the most effective by showing a melanogenesis inhibition up to four times greater than arbutin at 100 µM. Moreover, the antioxidant activity of the selected inhibitors was evaluated against H₂O₂ in amperometric experiments, whereby compound 7 was about three times more effective compared to compounds 1 and 6. The tyrosinase X-ray structure of Bacterium megaterium crystal was used to carry out molecular docking studies in the presence of compounds 1, 6 and 7 in comparison with that of kojic acid and arbutin, two conventional tyrosinase inhibitors. Molecular docking of compounds 6 and 7 confirmed the high affinity of these compounds to tyrosinase protein.

Curcumin and Its Derivatives Induce Apoptosis in Human Cancer Cells by Mobilizing and Redox Cycling Genomic Copper Ions

Turmeric spice contains curcuminoids, which are polyphenolic compounds found in the Curcuma longa plant’s rhizome. This class of molecules includes curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Using prostate cancer cell lines PC3, LNCaP, DU145, and C42B, we show that curcuminoids inhibit cell proliferation (measured by MTT assay) and induce apoptosis-like cell death (measured by DNA/histone ELISA). A copper chelator (neocuproine) and reactive oxygen species scavengers (thiourea for hydroxyl radical, superoxide dismutase for superoxide anion, and catalase for hydrogen peroxide) significantly inhibit this reaction, thus demonstrating that intracellular copper reacts with curcuminoids in cancer cells to cause DNA damage via ROS generation. We further show that copper-supplemented media sensitize normal breast epithelial cells (MCF-10A) to curcumin-mediated growth inhibition, as determined by decreased cell proliferation. Copper supplementation results in increased expression of copper transporters CTR1 and ATP7A in MCF-10A cells, which is attenuated by the addition of curcumin in the medium. We propose that the copper-mediated, ROS-induced mechanism of selective cell death of cancer cells may in part explain the anticancer effects of curcuminoids.

Synthetic Mono-Carbonyl Curcumin Analogues Attenuate Oxidative Stress in Mouse Models

Alzheimer’s disease is the commonest form of dementia associated with short-term memory loss and impaired cognition and, worldwide, it is a growing health issue. A number of therapeutic strategies have been studied to design and develop an effective anti-Alzheimer drug. Curcumin has a wide spectrum of biological properties. In this regard, the antioxidant potentials of mono-carbonyl curcumin analogues (h1−h5) were investigated using in vitro antioxidant assays and hippocampal-based in vivo mouse models such as light−dark box, hole board, and Y-maze tests. In the in vitro assay, mono-carbonyl curcumin analogues h2 and h3 with methoxy and chloro-substituents, respectively, showed promising 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2′-azinobis-3-ethylbenzothiazo-line-6-sulfonate (ABTS) free radical scavenging activities. In the in vivo studies, scopolamine administration significantly (p < 0.001) induced oxidative stress and memory impairment in mice, in comparison to the normal control group. The pretreatment with mono-carbonyl curcumin analogues, specifically h2 and h3, significantly decreased (123.71 ± 15.23 s (p < 0.001), n = 8; 156.53 ± 14.13 s (p < 0.001), n = 8) the duration of time spent in the light chamber and significantly enhanced (253.95 ± 19.05 s (p < 0.001), n = 8, and 239.57 ± 9.98 s (p < 0.001), n = 8) the time spent in the dark compartment in the light−dark box arena. The numbers of hole pokings were significantly (p < 0.001, n = 8) enhanced in the hole board test and substantially increased the percent spontaneous alternation performance (SAP %) in the Y-maze mouse models in comparison to the stress control group. In the biomarker analysis, the significant reduction in the lipid peroxidation (MDA) level and enhanced catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH) activities in the brain hippocampus reveal their antioxidant and memory enhancing potentials. However, further research is needed to find out the appropriate mechanism of reducing oxidative stress in pathological models.

Multiple health benefits of curcumin and its therapeutic potential

Turmeric, or Curcuma longa as it is formally named, is a multifunctional plant with numerous names. It was dubbed "the golden spice" and "Indian saffron" not only for its magnificent yellow color, but also for its culinary use. Turmeric has been utilized in traditional medicine since the dawn of mankind. Curcumin, demethoxycurcumin, and bisdemethoxycurcumin, which are all curcuminoids, make up turmeric. Although there have been significant advancements in cancer treatment, cancer death and incidence rates remain high. As a result, there is an increasing interest in discovering more effective and less hazardous cancer treatments. Curcumin is being researched for its anti-inflammatory, anti-cancer, anti-metabolic syndrome, neuroprotective, and antibacterial properties. Turmeric has long been used as a home remedy for coughs, sore throats, and other respiratory problems. As a result, turmeric and its compounds have the potential to be used in modern medicine to cure a variety of diseases. In this current review, we highlighted therapeutic potential of curcumin and its multiple health benefits on various diseases.

Synergistic, additive, and antagonistic antioxidant effects in the mixtures of curcumin with (-)-epicatechin and with a green tea fraction containing (-)-epicatechin

The combinations of curcumin with green tea flavan-3-ols produce various synergistic biological effects. This study aimed to verify the antioxidant effects in mixtures of curcumin with (-)-epicatechin (EC) or with EC fraction from green tea in a non-polar lipid system (triacylglycerol autoxidation) and in a polar conditions (ABTS assay). Curcumin was 2.5-2.6 and 2.9-3.6 times weaker antioxidant than EC and EC fraction, respectively. The synergism was found in mixtures using the isobologram analysis of ABTS^•+ scavenging activity results. The strongest effect with a combination index of 0.751 was in the equimolar mixture of pure compounds. In the lipid system, antagonism occurred for curcumin and EC fraction combination. However, an additive effect was found between curcumin and EC. In conclusion, the antioxidant effects in the curcumin and EC mixtures depended on the polarity of the assay media, the ratio of antioxidants, and presence other phenolics in the system.

Natural Chain-Breaking Antioxidants and Their Synthetic Analogs as Modulators of Oxidative Stress

Oxidative stress is associated with the increased production of reactive oxygen species or with a significant decrease in the effectiveness of antioxidant enzymes and nonenzymatic defense. The penetration of oxygen and free radicals in the hydrophobic interior of biological membranes initiates radical disintegration of the hydrocarbon “tails” of the lipids. This process is known as “lipid peroxidation”, and the accumulation of the oxidation products as peroxides and the aldehydes and acids derived from them are often used as a measure of oxidative stress levels. In total, 40 phenolic antioxidants were selected for a comparative study and analysis of their chain-breaking antioxidant activity, and thus as modulators of oxidative stress. This included natural and natural-like ortho-methoxy and ortho-hydroxy phenols, nine of them newly synthesized. Applied experimental and theoretical methods (bulk lipid autoxidation, chemiluminescence, in silico methods such as density functional theory (DFT) and quantitative structure–activity relationship ((Q)SAR) modeling) were used to clarify their structure–activity relationship. Kinetics of non-inhibited and inhibited lipid oxidation in close connection with inhibitor transformation under oxidative stress is considered. Special attention has been paid to chemical reactions resulting in the initiation of free radicals, a key stage of oxidative stress. Effects of substituents in the side chains and in the phenolic ring of hydroxylated phenols and biphenols, and the concentration were discussed.