Binding Of Curcumin Research Articles

Use of spectroscopic and zeta potential techniques to study the interaction between lysozyme and curcumin in the presence of silver nanoparticles at different sizes

This article describes, for the first time, the effect of three different sizes of silver nanoparticles on the binding of curcumin to lysozyme as examined by spectroscopic and zeta potential techniques at physiological conditions. The binding constants of curcumin to lysozyme in the presence of silver nanoparticles were measured. Based on the results of synchronous fluorescence and three-dimensional fluorescence spectroscopy, the presence of the different sizes of silver nanoparticles caused conformational changes in lysozyme during the binding of curcumin. Such changes were also observed when increasing the curcumin concentration. The results of fluorescence resonance energy transfer theory indicated that different sizes of silver nanoparticles could change the binding distance between curcumin and lysozyme. Based on the red edge excitation shift approach, we concluded that the limited mobility around the Trp residues decreased in the presence of silver nanoparticles with bigger size. Under resonance light scattering, the aggregation of curcumin on lysozyme in the presence of silver nanoparticles can play a major role in functional proteins.Communicated by Ramaswamy H. Sarma

Different curcumin forms selectively bind fibrillar amyloid beta in post mortem Alzheimer\u2019s disease brains: Implications for in-vivo diagnostics

The combined fluorescent and Aβ-binding properties of the dietary spice curcumin could yield diagnostic purpose in the search for a non-invasive Aβ-biomarker for Alzheimer’s disease (AD). However, evidence on the binding properties of curcumin, its conjugates and clinically used bio-available formulations to AD neuropathological hallmarks is scarce. We therefore assessed the binding properties of different curcumin forms to different neuropathological deposits in post-mortem brain tissue of cases with AD, other neurodegenerative diseases, and controls. Post mortem brain tissue was histochemically assessed for the binding of curcumin, its isoforms, conjugates and bio-available forms and compared to routinely used staining methods. For this study we included brains of early onset AD, late onset AD, primary age-related tauopathy (PART), cerebral amyloid angiopathy (CAA), frontotemporal lobar degeneration (FTLD) with tau or TAR DNA-binding protein 43 (TDP-43) inclusions, dementia with Lewy bodies (DLB), Parkinson’s disease (PD) and control cases without brain pathology. We found that curcumin binds to fibrillar amyloid beta (Aβ) in plaques and CAA. It does not specifically bind to inclusions of protein aggregates in FTLD-tau cases, TDP-43, or Lewy bodies. Curcumin isoforms, conjugates and bio-available forms show affinity for the same Aβ structures. Curcumin staining overlaps with immunohistochemical detection of Aβ in fibrillar plaques and CAA, and to a lesser extent cored plaques. A weak staining of neurofibrillary tangles was observed, while other structures immunopositive for phosphorylated tau remained negative. In conclusion, curcumin, its isoforms, conjugates and bio-available forms selectively bind fibrillar Aβ in plaques and CAA in post mortem AD brain tissue. Curcumin, being a food additive with fluorescent properties, is therefore an interesting candidate for in-vivo diagnostics in AD, for example in retinal fluorescent imaging.

Curcumin suppresses oncogenicity of human colon cancer cells by covalently modifying the cysteine 67 residue of SIRT1

SIRT1, an NAD+-dependent histone/protein deacetylase, has diverse physiological actions. Recent studies have demonstrated that SIRT1 is overexpressed in colorectal cancer, suggesting its oncogenic potential. However, the molecular mechanisms by which overexpressed SIRT1 induces the progression of colorectal cancer and its inhibition remain largely unknown. Curcumin (diferuloymethane), a major component of the spice turmeric derived from the plant Curcuma longa L., has been reported to exert chemopreventive and anti-carcinogenic effects on colon carcinogenesis. In the present study, we found that curcumin reduced the expression of SIRT1 protein without influencing its mRNA expression in human colon cancer cells, suggesting posttranslational regulation of SIRT1 by this phytochemical. Notably, ubiquitination and subsequent proteasomal degradation of SIRT1 were induced by curcumin treatment. Results of nano-LC-ESI-MS/MS revealed the direct binding of curcumin to cysteine 67 of SIRT1. In line with this result, the protein stability and clonogenicity of a mutant SIRT1 in which cysteine 67 was substituted by alanine were unaffected by curcumin. Taken together, these observations suggest that curcumin facilitates the proteasomal degradation of oncogenic SIRT1 through covalent modification of SIRT1 at the cysteine 67 residue.

Curcumin interacts directly with the Cysteine 259 residue of STAT3 and induces apoptosis in H-Ras transformed human mammary epithelial cells

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that is latent but constitutively activated in many types of cancers. It is well known that STAT3 plays a key role in inflammation-associated tumorigenesis. Curcumin is an anti-inflammatory natural compound isolated from the turmeric (Curcuma longa L., Zingiberaceae) that has been extensively used in a traditional medicine over the centuries. In the present study, we have found that curcumin inhibits STAT3 signaling that is persistently overactivated in H-Ras transformed breast epithelial cells (H-Ras MCF10A). Specific cysteine residues present in STAT3 appear to be critical for the activity as well as conformation of this transcription factor. We identified the cysteine residue 259 of STAT3 as a putative site for curcumin binding. Site-directed mutation of this cysteine residue abolished curcumin-induced inactivation of STAT3 and apoptosis in H-Ras MCF10A cells. The α,β-unsaturated carbonyl moiety of curcumin appears to be essential in its binding to STAT3 in H-Ras MCF10A cells. Tetrahydrocurcumin that lacks such electrophilic moiety failed to interact with STAT3 and to induce apoptosis in the same cell line. Taken together, our findings suggest that curcumin can abrogate aberrant activation of STAT3 through direct interaction, thereby inhibiting STAT3-mediated mammary carcinogenesis.

Curcumin/Turmeric as anEnvironment-Friendly Protein Gel Stain.

Curcumin, the main curcuminoid in food spice turmeric, is insoluble in water at room temperature. We showed that curcumin can be solubilized in water with the application of heat (100°C). Here we demonstrate that heat-solubilized curcumin can serve as a nontoxic and environment-friendly fluorescent/colorimetric reversible protein stain. Curcumin, the yellow pigment found in the rhizomes of the perennial herb Curcuma longa (turmeric), is insoluble in aqueous solvents. However, heat solubilization in water renders 1.5% of curcumin soluble. Curcumin solubilized by ethanol or alkali is ineffective in staining proteins. Heat-solubilized curry spice turmericalso stains proteins. Staining is achieved in 30min, with a sensitivity almost equaling that of Coomassie Brilliant Blue (CBB). Destaining is not required and excess curcumin/turmeric can be discarded into the sink. Binding of proteins by silver inhibits curcumin binding, suggesting similarity of protein binding by silver and curcumin. It costs $1.5-2.0 to stain a mini-gel with curcumin, while turmeric costs less than 0.005 cent. CBB staining/destaining costs about two cents. Curcumin/turmeric, thus, can serve as an ideal nontoxic protein stain.

Specific interactions between mycobacterial FtsZ protein and curcumin derivatives: Molecular docking and ab initio molecular simulations

Filamentous temperature-sensitive Z (FtsZ) protein plays essential role in bacteria cell division, and its inhibition prevents Mycobacteria reproduction. Here we adopted curcumin derivatives as candidates of novel inhibitors and investigated their specific interactions with FtsZ, using ab initio molecular simulations based on protein–ligand docking, classical molecular mechanics and ab initio fragment molecular orbital (FMO) calculations. Based on FMO calculations, we specified the most preferable site of curcumin binding to FtsZ and highlighted the key amino acid residues for curcumin binding at an electronic level. The result will be useful for proposing novel inhibitors against FtsZ based on curcumin derivatives.

Biochemical and Biophysical characterization of curcumin binding to human mitotic kinesin Eg5: Insights into the inhibitory mechanism of curcumin on Eg5

In this study we have characterized the biochemical and biophysical interactions of curcumin with the mitotic kinesin Eg5 which plays a pivotal role in the separation of centrosomes during cell division. Curcumin bound to the purified Eg5 (Eg5-437H) with a Kd value of 7.8μM. The temperature dependent binding analysis and evaluation of thermodynamic parameters indicated the involvement of static quenching mechanism in the binding process. Evidences from competition experiment with monastrol indicated that curcumin bound to Eg5 at a novel druggable site. Using Förster resonance energy transfer the distance between curcumin and monastrol binding site from TRP127 on Eg5-437H was found to be 33Å and 17Å respectively. Curcumin inhibited the ATPase activity of Eg5 motor and perturbed the dynamic interactions between Eg5 and microtubules. Results from circular dichroism studies and molecular dynamics simulations suggest that curcumin binding might perturb the Eg5-437H secondary structure which could be the reason behind its inhibitory effects on Eg5. Cell culture studies performed in HeLa cells indicated that curcumin potentiated the mitotic arrest and monopolar spindle formation in synergism with monastrol, indicating that both ligands could bind simultaneously to the same target.

Effects of length and unsaturation of the alkyl chain on the hydrophobic binding of curcumin with Tween micelles

This work studies the effects of length and unsaturation of alkyl chain on the hydrophobic binding of curcumin with Tween 20, 60 and 80 micelles. While Tween 20 and 60 possess 12 and 18 saturated carbons, respectively, in their alkyl chains, the alkyl chain of Tween 80, with one double bond, has the same length as Tween 60. Tween 60 micelles are superior to Tween 20 and 80 micelles for improving curcumin stability. The fluorescence measurement suggests that Tween 60 micelles provide curcumin with the most hydrophobic microenvironment, owing to the long and saturated alkyl chain of Tween 60. The pKa1 and binding constants of curcumin have the same order of Tween 60 > Tween 20 > Tween 80. These results show that the length increase, and unsaturation, of the alkyl chain of Tween surfactants have opposite effects on the hydrophobic binding of curcumin with Tween micelles.

Thermodynamic and kinetic analyses of curcumin and bovine serum albumin binding

Bovine serum albumin (BSA)/curcumin binding and dye photodegradation stability were evaluated. BSA/curcumin complex showed 1:1 stoichiometry, but the thermodynamic binding parameters depended on the technique used and BSA conformation. The binding constant was of the order of 105L·mol−1 by fluorescence and microcalorimetric, and 103 and 104L·mol−1 by surface plasmon resonance (steady-state equilibrium and kinetic experiments, respectively). For native BSA/curcumin, fluorescence indicated an enthalpic and entropic driven process based on the standard enthalpy change (ΔH○F=−8.67kJ·mol−1), while microcalorimetry showed an entropic driven binding process (ΔH○cal=29.11kJ·mol−1). For the unfolded BSA/curcumin complex, it was found thatp ΔH○F=−16.12kJ·mol−1 and ΔH○cal=−42.63kJ·mol−1. BSA (mainly native) increased the curcumin photodegradation stability. This work proved the importance of using different techniques to characterize the protein-ligand binding.

Isolation and characterization of iron chelators from turmeric (Curcuma longa): selective metal binding by curcuminoids.

Iron overload disorders may be treated by chelation therapy. This study describes a novel method for isolating iron chelators from complex mixtures including plant extracts. We demonstrate the one-step isolation of curcuminoids from turmeric, the medicinal food spice derived from Curcuma longa. The method uses iron-nitrilotriacetic acid (NTA)-agarose, to which curcumin binds rapidly, specifically, and reversibly. Curcumin, demethoxycurcumin, and bisdemethoxycurcumin each bound iron-NTA-agarose with comparable affinities and a stoichiometry near 1. Analyses of binding efficiencies and purity demonstrated that curcuminoids comprise the primary iron binding compounds recovered from a crude turmeric extract. Competition of curcuminoid binding to the iron resin was used to characterize the metal binding site on curcumin and to detect iron binding by added chelators. Curcumin-Iron-NTA-agarose binding was inhibited by other metals with relative potency: (>90% inhibition) Cu2+~Al3+>Zn2+≥Ca2+~Mg2+~Mn2+ (<20% inhibition). Binding was also inhibited by pharmaceutical iron chelators (desferoxamine or EDTA) or by higher concentrations of weak iron chelators (citrate or silibinin). Investigation of the physiological effects of iron binding by curcumin revealed that curcumin uptake by cultured cells was reduced>80% by addition of iron to the media; uptake was completely restored by desferoxamine. Ranking of metals by relative potencies for blocking curcumin uptake agreed with their relative potencies in blocking curcumin binding to iron-NTA-agarose. We conclude that curcumin can selectively bind toxic metals including iron in a physiological setting, and propose inhibition of curcumin binding to iron-NTA-agarose for iron chelator screening.

Probing the binding of resveratrol, genistein and curcumin with chitosan nanoparticles

The conjugation of antioxidant polyphenols resveratrol, genistein and curcumin with chitosan-15 and chitosan-100kDa was studied in aqueous solution at physiological conditions, using multiple spectroscopic methods, TEM images and docking studies. Structural analysis showed that polyphenol bindings are via hydrophilic, hydrophobic and H-bonding contacts with resveratrol forming more stable conjugates. As chitosan size increased, the binding efficacy and stability of polyphenol-polymer adducts were increased. Polyphenol binding induced major alterations of chitosan morphology. Chitosan nanoparticles are capable of delivery of polyphenols in vitro.

Abstract 1250: Curcumin inhibits migration and growth of human colon cancer cells through covalent modification of oncogenic SIRT1: Cysteine 67 as a potential binding site

Abstract Silent mating type information regulator 2 homolog 1 (SIRT1), an NAD+-dependent histone/protein deacetylase, has diverse physiological functions, including metabolic regulation and stress response. Despite extensive research, however, the role of SIRT1 in tumorigenesis remains controversial. Recent studies have demonstrated that SIRT1 is abnormally overexpressed in several human malignancies, and elevated levels of SIRT1 are correlated with the tumor invasion and metastasis. Curcumin (diferuloymethane), a major component of the spice turmeric (Curcuma longa L.), has been reported to possess anti-inflammatory and anti-carcinogenic properties. In the present study, we found that SIRT1 is predominantly overexpressed in the cytoplasm of several colorectal cancer cells as well as colon tumors. Curcumin abrogated migration and colony forming capability of human colon cancer (HCT-116) cells. This prompted us to investigate the effect of curcumin on the expression of SIRT1 and underlying molecular mechanisms in the context of its inhibition of the migration and growth of these cells. When HCT-116 cells were treated with curcumin, the protein expression of SIRT1 was significantly reduced, but the level of its mRNA transcript remained unchanged. The curcumin-induced suppression of SIRT1 protein expression was abrogated by the proteasomal inhibitor, MG-132. When HCT-116 cells were treated with curcumin, ubiquitination of SIRT1 was elevated. Notably, tetrahydrocurcumin, a non-electrophilic analogue of curcumin that lacks the α,β-unsaturated carbonyl moiety, failed to ubiquitinate and degrade SIRT1. Nano-LC-ESI-MS/MS analysis revealed the modification of the SIRT1 cysteine 67 residue. In line with this observation, the protein stability of a mutant SIRT1 in which cysteine 67 was replaced by alanine (SIRT1-C67A) was unaffected by curcumin treatment. Furthermore, migration and anchorage-independent growth of cells expressing SIRT1-C67A were barely inhibited by curcumin compared with those in cells harbouring wild-type SIRT1. Lysates of HCT-116 cells incubated with curcumin-conjugated Sepharose 4B beads exhibited covalent binding of curcumin to SIRT1. However, such direct interaction was markedly reduced in cells with SIRT1 cysteine 67 mutation. Taken together, these findings suggest that curcumin exerts inhibitory effects on progression of colon cancer through destabilization of oncogenic SIRT1. The electrophilic α,β-unsaturated carbonyl group present in curcumin can covalently modify SIRT1, preferentially at the cysteine 67 residue, facilitating its degradation via the ubiquitin-proteasome pathway in HCT-116 cells. Citation Format: Yeon-Hwa Lee, Na-Young Song, Do-Hee Kim, Hye-Kyung Na, Young-Joon Surh. Curcumin inhibits migration and growth of human colon cancer cells through covalent modification of oncogenic SIRT1: Cysteine 67 as a potential binding site [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1250. doi:10.1158/1538-7445.AM2017-1250

Improved antioxidant activity and physicochemical properties of curcumin by adding ovalbumin and its structural characterization

Protein as a carrier to improve the solubility and bioavailability of curcumin has been studied widely. However, to date the researches were mainly focused on its binding mechanism and the applications in aqueous solution. Systematic study on the characteristics and properties of the complex in solid phase after the binding of curcumin with protein is scarce. In this work, a powder composite of curcumin bound to ovalbumin was prepared by freeze-drying. The FTIR and X-ray diffraction results indicated that the crystal structure of curcumin and secondary structure of ovalbumin were changed because of the binding of curcumin to ovalbumin, leading to the formation of an amorphous complex with the sizes in the range of 924.20 ± 72.34 nm. Thermogravimetric analysis showed that the maximum weight loss point of ovalbumin/curcumin complex was at 289 °C, which was lower than that of pure ovalbumin and curcumin, implying that the complex was more prone to pyrolyze. Furthermore, the improved antioxidant activity was evaluated by DPPH radical scavenging activity and reducing power assay compared with pure ovalbumin and curcumin. This work could help to understand the characteristics of the curcumin-protein complex which has the potential to be applied in functional foods.

Binding, stability, and antioxidant activity of curcumin with self-assembled casein–dextran conjugate micelles

ABSTRACTThis work studied the potential of self-assembled micelles of casein–dextran conjugates (CD) as a protective carrier for bioactive curcumin. CD was prepared through the Amadori rearrangement of the Maillard reaction. In casein micelles and CD micelles, the addition of curcumin can quench the intrinsic fluorescence of casein gradually. According to the double logarithm equation, the binding constants were determined as 3.9 × 104 and 1.8 × 105 M−1 for the binding of curcumin with casein micelles and CD micelles, respectively. The higher affinity of hydrophobic binding of curcumin with CD micelles was ascribed to the more hydrophobic and compact structure of casein core surrounded by the hydrophilic dextran shell, which was supported by the fluorescence spectrum and fluorescence anisotropy of curcumin. Furthermore, CD micelles were found to be superior to casein micelles for improving the stability and radical scavenging activity of curcumin.

Curcumin coated gold nanoparticles: synthesis, characterization, cytotoxicity, antioxidant activity and its comparison with citrate coated gold nanoparticles

Objective(s): Biological applications of gold nanoparticles have limitations because of the toxic chemicals used in their synthesis. Curcumin can be used as reducing as well as capping agent in synthesis of GNPs to eliminate the cytotoxicity. Conjugation of curcumin to gold also helps in increasing its solubility and bioavailability. Materials and Methods: Here we report synthesis of gold nanoparticles coated with citrate and curcumin and of two different sizes via chemical routes. UV-Vis absorbance spectroscopy, Dynamic Light Scattering and Transmission Electron Microscopy were applied to study the average particle size, size stability of the samples and zeta potential. Fourier transform infrared, Raman Spectroscopy and Fluorescence Spectroscopy were applied for detection of curcumin on the surface of GNPs. The antioxidant activity was evaluated using DPPH assay and Cytotoxicity was evaluated by MTT assay.Results: Particles were synthesized of 6 and 16 nm size. The average particle size was found to be 21.7 ± 5.7 by TEM. The zeta potential on the surface of Cur-GNPs was negative and larger than 25 mV which is a sign of their high stability. The stability of these particles (with different coatings but with similar sizes) at different time intervals (up to 3 months) and also in different media like cell culture medium, different buffers, glucose and at different pH conditions have been investigated thoroughly. Appearance of functional groups assigned to curcumin in FTIR and SERS spectra are sign of presence of curcumin in the sample. The quenching of the fluorescence in the presence of GNPs reveals the clear indication of the capping and binding of curcumin with GNPs. Cur-GNP1 (16 nm) were found to exhibit highest antioxidant activity than other gold nanoparticles. Cytotoxicity evaluation using MTT assay on L929 cell line proved curcumin coated gold nanoparticles were non-toxic up to 40 ppm.Conclusion: The results revealed that larger curcumin coated gold nanoparticles were stable and also non-toxic and were found suitable for further in-vitro and in-vivo studies.

Modulation in the conformational and stability attributes of the Alzheimer’s disease associated amyloid-beta mutants and their favorable stabilization by curcumin: molecular dynamics simulation analysis

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by progressive accumulation of amyloid-beta (Aβ) peptides in brain. In the present study, two familial Aβ42 mutations, namely A2V (harmful) and A2T (protective) have been analyzed and compared with the wild-type (WT) by performing all-atom molecular dynamics (MD) simulations in the absence and presence of curcumin, a well-known inhibitor of Aβ plaque formation. Mutant A2V was found to exhibit highest stability followed by WT and mutant A2T in the absence of curcumin. This stability trend was found to be reversed in the presence of curcumin, suggesting a significant change in the conformational landscape of Aβ42 folding. Due to significant differences in the folding and interaction patterns of the mutants A2V and A2T, curcumin exhibited higher binding affinity for mutant A2T as compared to that of A2V. To the best of our knowledge, this is the first report on the effect of curcumin binding on structural landscapes of the two contrasting point mutants providing an understanding of the basis of Aβ plaque formation and its prevention by curcumin.

Hydrophobic kenaf nanocrystalline cellulose for the binding of curcumin

Nanocrystalline cellulose (NCC) extracted from lignocellulosic materials has been actively investigated as a drug delivery excipients due to its large surface area, high aspect ratio, and biodegradability. In this study, the hydrophobically modified NCC was used as a drug delivery excipient of hydrophobic drug curcumin. The modification of NCC with a cationic surfactant, cetyl trimethylammonium bromide (CTAB) was used to modulate the loading of hydrophobic drugs that would not normally bind to NCC. The FTIR, Elemental analysis, XRD, TGA, and TEM were used to confirm the modification of NCC with CTAB. The effect of concentration of CTAB on the binding efficiency of hydrophobic drug curcumin was investigated. The amounts of curcumin bound onto the CTAB–NCC nanoparticles were analyzed by UV–vis Spectrophotometric. The result showed that the modified CTAB–NCC bound a significant amount of curcumin, in a range from 80% to 96% curcumin added. Nevertheless, at higher concentration of CTAB resulted in lower binding efficiency.

Curcumin-primed and curcumin-loaded exosomes: potential neural therapy.

Curcumin-primed and curcumin-loaded exosomes: potential neural therapy.

Solubility profiles, hydration and desolvation of curcumin complexed with γ-cyclodextrin and hydroxypropyl-γ-cyclodextrin

In this study, we investigated curcumin (CUR) solubility profiles and hydration/desolvation effects of this substance formulated with γ-cyclodextrin (γ-CD) and hydroxypropyl-γ-cyclodextrin (HP-γ-CD) excipients. The CUR/HP-γ-CD complex was found to be more stable in solution with the highest apparent stability constant for CUR/HP-γ-CD (Kc = 1.58*104 M−1) as the more soluble form in distilled water. The in silico calculations, including molecular docking, Monte Carlo (MC), and molecular dynamics (MD) simulations, indicated that water molecules play an important role in host-guest complexation mediating the CUR binding to cyclodextrins via hydrogen bond formations. The CUR hydration/desolvation effects contributed to the complex formation by elevating the CUR binding affinity to both CDs. The CUR/HP-γ-CD complex after the CUR hydration was determined with a minimal Gibbs free energy of binding (ΔGbind = −9.93 kcal*mol−1) due to the major hydrophobic (vdW) forces. Overall, the results of this study can aid a development of cyclodextrin-based drug delivery vectors, signifying the importance of water molecules during the formulation processes.

A comprehensive approach to ascertain the binding mode of curcumin with DNA

Curcumin is a natural phytochemical from the rhizoma of Curcuma longa, the popular Indian spice that exhibits a wide range of pharmacological properties like antioxidant, anticancer, anti-inflammatory, antitumor, and antiviral activities. In the published literatures we can see different studies and arguments on the interaction of curcumin with DNA. The intercalative binding, groove binding and no binding of curcumin with DNA were reported. In this context, we conducted a detailed study to understand the mechanism of recognition of dimethylsulfoxide-solubilized curcumin by DNA. The interaction of curcumin with calf thymus DNA (ctDNA) was confirmed by agarose gel electrophoresis. The nature of binding and energetics of interaction were studied by Isothermal Titration Calorimetry (ITC), Differential Scanning Calorimetry (DSC), UV–visible, fluorescence and melting temperature (Tm) analysis. The experimental data were compared with molecular modeling studies. Our investigation confirmed that dimethylsulfoxide-solubilized curcumin binds in the minor groove of the ctDNA without causing significant structural alteration to the DNA.