Curcumin–amino acid conjugates: Synthesis, antioxidant and antimutagenic attributes

Synthesis of Curcumin Derivatives via Knoevenagel Reaction Within a Continuously Driven Microfluidic Reactor Using Polymeric Networks Containing Piperidine as a Catalyst

The use of organo-catalysis in continuous-flow reactor systems is gaining attention in medicinal chemistry due to its cost-effectiveness and reduced chemical waste. In this study, bioactive curcumin (CUM) derivatives were synthesized in a continuously operated microfluidic reactor (MFR), using piperidine-based polymeric networks as catalysts. Piperidine methacrylate and piperidine acrylate were synthesized and subsequently copolymerized with complementary monomers (MMA or DMAA) and crosslinkers (EGDMA or MBAM) via photopolymerization, yielding different polymeric networks. Initially, batch reactions were optimized for the organo-catalytic Knoevenagel condensation between CUM and 4-nitrobenzaldehyde, under various conditions, in the presence of polymer networks. Conversion was assessed using offline 1H NMR spectroscopy, revealing an increase in conversion with enhanced swelling properties of the polymer networks, which facilitated greater accessibility of catalytic sites. In continuous-flow MFR experiments, optimized polymer gel dots exhibited superior catalytic performance, achieving a conversion of up to 72%, compared to other compositions. This improvement was attributed to the enhanced swelling in the reaction mixture (DMSO/methanol, 7:3 v/v) at 40 °C over 72 h. Furthermore, the MFR system enabled the efficient synthesis of a series of CUM derivatives, demonstrating significantly higher conversion rates than traditional batch reactions. Notably, while batch reactions required 90% catalyst loading in the gel, the MFR system achieved a comparable or superior performance with only 50% catalyst, resulting in a higher turnover number. These findings underscore the advantages of continuous-flow organo-catalysis in enhancing catalytic efficiency and sustainability in organic synthesis.

Esterified Indole-3-propionic Acid: A Novel Inhibitor against Cholinesterase Identified through Experimental and Computational Approaches

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are targeted for designing drugs against cognitive dysfunction. Curcumin (CUR) and indole-3-propionic acid (IPA) are known for their neuroprotective activity. The clinical application of CUR is hindered due to poor absorption and bioavailability. Hence, CUR was conjugated with IPA to form the CUR-IPA diester. CUR-IPA inhibition against electric eel AChE (eAChE), human AChE (hAChE), and hBChE was carried out. In silico and molecular dynamics (MD) analyses of the interaction of CUR-IPA with hAChE and hBChE were done. UV-visible spectroscopy (λmax at 415 and 276 nm), NMR spectrum, and ESI/MS/MS [m/z = 711 (M + H)] confirmed CUR-IPA formation. CUR-IPA showed in vitro antioxidant activity. The IC50 values of eAChE, hAChE, and hBChE enzyme inhibition were 5.66, 59.30, and 60.66 μM, respectively. MD simulation-based analysis such as RMSD, RMSF, free-energy calculation, PCA, FEL, and DCCM confirmed the stable binding of CUR-IPA with hAChE and hBChE. Further QM/MM analysis confirmed the stable interaction of CUR-IPA with hAChE and hBChE. Since CUR-IPA showed in vitro inhibition against AChE and BChE, a further neuroprotective effect in in vivo could be studied.

Synthesis, Cytotoxicity, and Mechanistic Evaluation of Tetrahydrocurcumin-Amino Acid Conjugates as LAT1-Targeting Anticancer Agents in C6 Glioma Cells

Glioblastoma, a fatal brain cancer with limited treatments and poor prognosis, could benefit from targeting the L-type amino acid transporter I (LAT1). LAT1 is essential for cancer cells to acquire necessary amino acids. Tetrahydrocurcumin (THC), a key curcumin derivative, shows potential for glioblastoma treatment. However, its effectiveness is hindered by poor physicochemical and pharmacokinetic properties. Therefore, this study aims to improve the therapeutic efficacy of THC against glioblastoma by chemically modifying it to target LAT1. A novel series of THC-amino acid conjugates were synthesized by conjugating five amino acids: glycine, leucine, isoleucine, and phenylalanine to THC via carbamate bonds. The therapeutic efficacy of THC-amino acid conjugates was further examined in C6 glioma cells, including the role of LAT1 in their therapeutic effects. Among the conjugates tested, THC conjugated with two phenylalanines (THC-di-Phe) showed remarkably higher cytotoxicity against C6 glioma cells (35.8 μM) compared to THC alone (110.7 μM). THC-di-Phe induced cellular death via necrosis and apoptosis, outperforming THC. Additionally, THC-di-Phe inhibited C6 cell proliferation and migration more effectively than THC. Co-incubation of THC-di-Phe with the LAT1 inhibitor 2-Aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) further increased cellular death. THC-di-Phe also significantly inhibited the P70SK/S6 pathway, regulated by LAT1 inhibitors, more effectively than THC and displayed a similar binding mode with both JX-075 and BCH to the active site of LAT1. Findings suggest the potential role of THC-di-Phe as a LAT1 inhibitor and provide novel insight into its use as a potent antitumor agent in glioma with increased therapeutic efficacy.

Synthesis, Anticancer Activity, and Molecular Docking of New 1,2,3-Triazole Linked Tetrahydrocurcumin Derivatives

Cancer is one of the deadliest diseases to humanity. There is significant progress in treating this disease, but developing some drugs that can fight this disease remains a challenge in the field of medical research. Thirteen new 1,2,3-triazole linked tetrahydrocurcumin derivatives were synthesized by click reaction, including a 1,3-dipolar cycloaddition reaction of tetrahydrocurcumin baring mono-alkyne with azides in good yields, and their in vitro anticancer activity against four cancer cell lines, including human cervical carcinoma (HeLa), human lung adenocarcinoma (A549), human hepatoma carcinoma (HepG2), and human colon carcinoma (HCT-116) were investigated using MTT(3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetraz-olium bromide) assay. The newly synthesized compounds had their structures identified using NMR HRMS and IR techniques. Some of prepared compounds, including compounds 4g and 4k, showed potent cytotoxic activity against four cancer cell lines compared to the positive control of cisplatin and tetrahydrocurcumin. Compound 4g exhibited anticancer activity with a IC50 value of 1.09 ± 0.17 μM against human colon carcinoma HCT-116 and 45.16 ± 0.92 μM against A549 cell lines compared to the positive controls of tetrahydrocurcumin and cisplatin. Moreover, further biological examination in HCT-116 cells showed that compound 4g can arrest the cell cycle at the G1 phase. A docking study revealed that the potential mechanism by which 4g exerts its anti-colon cancer effect may be through inhabiting the binding of APC-Asef. Compound 4g can be used as a promising lead for further exploration of potential anticancer agents.

Preparation of valine-curcumin conjugate and its in vitro antibacterial and antitumor activity and in vivo biological effects on American eels (Anguilla rostrata)

Curcumin (Cur) exhibits diverse natural pharmacological activities, despite its limited water solubility (hydrophobicity) and low bioavailability. In this investigation, a valine-curcumin conjugate (Val-Cur) was synthesized through amino acid side chain modification, and its solubility increased to 1.78 mg/mL. In vitro experimental findings demonstrated that the antibacterial activity of Val-Cur against Escherichia coli, Staphylococcus aureus, Aeromonas hydrophila, and Vibrio parahaemolyticus was significantly superior to that of Cur. The inhibition rate of Val-Cur against HepG2 (human hepatocellular carcinoma) cells was higher than that of Cur at low concentrations (below 25 μmol/L), although the IC50 value of Val-Cur did not differ significantly from that of Cur. In vivo biological effects of Val-Cur were assessed by adding it into the feed (150 mg/kg) of American eels (Anguilla rostrata). Val-Cur significantly improved the growth performance (↑weight gain rate, ↑specific growth rate, and ↓feed conversion rate) and activities of intestinal digestive enzymes (amylase and lipase) and antioxidant enzymes (superoxide dismutase) in American eels. Additionally, Val-Cur significantly improved serum biochemical indices (↑high-density lipoprotein cholesterol, ↓low-density lipoprotein cholesterol, ↓aspartate and alanine aminotransferases). Furthermore, Val-Cur increased intestinal microbial diversity, reduced the abundance of potentially pathogenic bacteria (Spiroplasma, Clostridium, and Pseudomonas), and elevated the abundance of beneficial digestion-promoting bacteria (Romboutsia, Phyllobacterium, Romboutsia sedimentorum, and Clostridium butyricum) conducive to glucose metabolism (P < 0.05). To the best of our knowledge, this study is the first to explore water-soluble curcumin in aquaculture, and the findings will lay the groundwork for the potential application of water-soluble curcumin in the field of aquaculture.

Curcumin - Bioavailability Enhancement by Prodrug Approach and Novel Formulations

Curcumin is a diverse natural pharmacological agent involved in various signal transduction mechanisms. Therapeutically, this potent molecule faces different challenges and issues related to low bioavailability due to its poor aqueous solubility, less permeability, faster elimination and clearance. Experts in synthetic chemistry and pharmaceuticals are continuously sparing their efforts to overcome these pharmacokinetic challenges by using different structural modification strategies and developing novel drug delivery systems. In this mini-review article, we are focusing on development of curcumin derivatives by different possible routes like conjugation with biomolecules, natural polymers, synthetic polymers, natural products, metal conjugates and co- administration with natural metabolic inhibitors. In addition to that, it was also focused on the preparation of modified formulations such as micelles, microemulsions, liposomes, complexes with phospholipids, micro and nanoemulsions, solid lipid nanoparticles, nano lipid carriers, biopolymer nanoparticles and microgels to improve the pharmacokinetic properties of the curcumin without altering its pharmacodynamics activity. This review helps to understand the problems associated with curcumin and different strategies to improve its pharmacokinetic profile.

Tetrahydrocurcumin Derivatives Enhanced the Anti-Inflammatory Activity of Curcumin: Synthesis, Biological Evaluation, and Structure-Activity Relationship Analysis

Tetrahydrocurcumin, the most abundant curcumin transformation product in biological systems, can potentially be a new alternative therapeutic agent with improved anti-inflammatory activity and higher bioavailability than curcumin. In this article, we describe the synthesis and evaluation of the anti-inflammatory activities of tetrahydrocurcumin derivatives. Eleven tetrahydrocurcumin derivatives were synthesized via Steglich esterification on both sides of the phenolic rings of tetrahydrocurcumin with the aim of improving the anti-inflammatory activity of this compound. We showed that tetrahydrocurcumin (2) inhibited TNF-α and IL-6 production but not PGE2 production. Three tetrahydrocurcumin derivatives inhibited TNF-α production, five inhibited IL-6 production, and three inhibited PGE2 production. The structure-activity relationship analysis suggested that two factors could contribute to the biological activities of these compounds: the presence or absence of planarity and their structural differences. Among the tetrahydrocurcumin derivatives, cyclic compound 13 was the most active in terms of TNF-α production, showing even better activity than tetrahydrocurcumin. Acyclic compound 11 was the most effective in terms of IL-6 production and retained the same effect as tetrahydrocurcumin. Moreover, acyclic compound 12 was the most active in terms of PGE2 production, displaying better inhibition than tetrahydrocurcumin. A 3D-QSAR analysis suggested that the anti-inflammatory activities of tetrahydrocurcumin derivatives could be increased by adding bulky groups at the ends of compounds 2, 11, and 12.

Cationic Ester Prodrugs of Curcumin with N,N-dimethyl Amino Acid Promoieties Improved Poor Water Solubility and Intestinal Absorption

PURPOSE

Although curcumin (Cur) has powerful pharmacological effects, its use in medicine has not been established yet. The oral bioavailability (BA) of Cur is limited because of its poor water solubility. The purpose of this study was to confirm whether cationic N,N-dimethyl amino acid esters of Cur could act as prodrugs and improve its water solubility and oral bioavailability.

METHODS

Two N,N-dimethyl amino acid esters of Cur were synthesized. The hydrolysis profile of the esters was evaluated using rat and human microsomes. A pharmacokinetic study after oral administration of the Cur ester derivatives was performed in rats and compared to the administration of suspended or dissolved Cur formulation. The anti-inflammatory effects of the Cur derivatives were evaluated using macrophage RAW 264.7 stimulated with lipopolysaccharide.

RESULTS

Cur ester derivatives showed  > 200 mM water solubility. The derivatives were reconverted to the parent compound (Cur) after cleavage of the ester bonds by microsomal esterase, indicating that the compounds could act as Cur prodrugs. The Cur prodrugs enhanced the absolute oral bioavailability of Cur by a 9- and threefold increase of suspended and dissolved Cur administration, respectively, thereby improving intestinal absorption. Cur prodrugs strongly attenuated COX2, iNOS, and ERK phosphorylation.

CONCLUSIONS

The cationic N,N-dimethyl amino acid ester prodrugs of Cur improved the water solubility of Cur and enhanced oral bioavailability in rats. These Cur prodrugs may be good candidates for developing medicinal options previously unavailable due to the poor water solubility and oral BA of Cur.

Polyphenols with Anti-Inflammatory Properties: Synthesis and Biological Activity of Novel Curcumin Derivatives

Herein, we describe the synthesis and evaluation of anti-inflammatory activities of new curcumin derivatives. The thirteen curcumin derivatives were synthesized by Steglich esterification on one or both of the phenolic rings of curcumin with the aim of providing improved anti-inflammatory activity. Monofunctionalized compounds showed better bioactivity than the difunctionalized derivatives in terms of inhibiting IL-6 production, and known compound 2 presented the highest activity. Additionally, this compound showed strong activity against PGE₂. Structure-activity relationship studies were carried out for both IL-6 and PGE₂, and it was found that the activity of this series of compounds increases when a free hydroxyl group or aromatic ligands are present on the curcumin ring and a linker moiety is absent. Compound 2 remained the highest activity in modulating IL-6 production and showed strong activity against PGE₂ synthesis.

Amino-Acid-Conjugated Natural Compounds: Aims, Designs and Results

Protein is one of the essential macronutrients required by all living things. The breakdown of protein produces monomers known as amino acids. The concept of conjugating natural compounds with amino acids for therapeutic applications emerged from the fact that amino acids are important building blocks of life and are abundantly available; thus, a greater shift can result in structural modification, since amino acids contain a variety of sidechains. This review discusses the data available on amino acid–natural compound conjugates that were reported with respect to their backgrounds, the synthetic approach and their bioactivity. Several amino acid–natural compound conjugates have shown enhanced pharmacokinetic characteristics, including absorption and distribution properties, reduced toxicity and increased physiological effects. This approach could offer a potentially effective system of drug discovery that can enable the development of pharmacologically active and pharmacokinetically acceptable molecules.

Synthesis, cytotoxicity evaluation and molecular docking studies on 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone derivatives

2′,4′-Dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (DMC, 1) was isolated from seeds of Syzygium nervosum A.Cunn. ex DC. exhibiting intriguing biological activities. Herein, thirty three DMC derivatives including 4′-O-monosubstituted-DMC (2), 7-O-acylated-4-hydroxycoumarin derivatives (3), stilbene–coumarin derivatives (4), 2′,4′-disubstituted-DMC (5), and flavanone derivatives (6), were synthesised through acylation, alkylations, and sulfonylation. These semi-synthetic DMC derivatives were evaluated for in vitro cytotoxicity against six carcinoma cell lines. It was found that most derivatives exhibited higher cytotoxicity than DMC. In particular, 4′-O-caproylated-DMC (2b) and 4′-O-methylated-DMC (2g) displayed the strongest cytotoxicity against SH-SY5Y with IC₅₀ values of 5.20 and 7.52 μM, respectively. Additionally, 4′-O-benzylated-DMC (2h) demonstrated the strongest cytotoxicity against A-549 and FaDu with IC₅₀ values of 9.99 and 13.98 μM, respectively. Our structure–activity relationship (SAR) highlights the importance of 2′-OH and the derivatisation pattern of 4′-OH. Furthermore, molecular docking simulation studies shed further light on how these bioactive compounds interact with cyclin-dependent kinase 2 (CDK2).

Semi-synthetic DMC derivatives were synthesised and displayed biological potency against various cancer cell lines.

Mechanistic Insight into the Effects of Curcumin on Neuroinflammation-Driven Chronic Pain

Chronic pain is a persistent and unremitting condition that has immense effects on patients' quality of life. Studies have shown that neuroinflammation is associated with the induction and progression of chronic pain. The activation of microglia and astrocytes is the major hallmark of spinal neuroinflammation leading to neuronal excitability in the projection neurons. Excessive activation of microglia and astrocytes is one of the major contributing factors to the exacerbation of pain. However, the current chronic pain treatments, mainly by targeting the neuronal cells, remain ineffective and unable to meet the patients' needs. Curcumin, a natural plant product found in the Curcuma genus, improves chronic pain by diminishing the release of inflammatory mediators from the spinal glia. This review details the role of curcumin in microglia and astrocytes both in vitro and in vivo and how it improves pain. We also describe the mechanism of curcumin by highlighting the major glia-mediated cascades in pain. Moreover, the role of curcumin on inflammasome and epigenetic regulation is discussed. Furthermore, we discuss the strategies used to improve the efficacy of curcumin. This review illustrates that curcumin modulating microglia and astrocytes could assure the treatment of chronic pain by suppressing spinal neuroinflammation.

Synthesis of linear polyglucoside and inhibition on the amyloid fibril formation of hen egg white lysozyme

A novel polymer poly (6-O-MMAGlc) has been synthesized via free radical polymerization of monomer methyl 6-O-methacryloyl-α-D-glucoside (6-O-MMAGlc) and characterized. The influence of poly(6-O-MMAGlc) on the formation of hen egg white lysozyme (HEWL) amyloid fibril was detailly investigated, indicating that the polymer could effectively inhibit the formation of HEWL amyloid fibril. The formation kinetics of HEWL amyloid fibril with the presence of poly(6-O-MMAGlc) was measured by Thioflavin T (ThT) fluorescence method, demonstrating that poly(6-O-MMAGlc) could significantly inhibit the amyloid fibril formation of HEWL in a dose-dependent manner. The inhibitory result was furtherly illustrated by congo red (CR) binding assay, 8-anilino-1-naphthalenesulfonic acid (ANS) fluorescence assay, circular dichroism (CD) spectroscopy and transmission electron microscope (TEM).

Synthesis, pharmacological profile and 2D-QSAR studies of curcumin-amino acid conjugates as potential drug candidates

A series of curcumin bis-conjugates 3a-q, 5a-k and 6a-k were synthesized in good yields utilizing an optimized reaction condition. We explored the effect of different amino acids and protecting groups on biological activities of curcumin. The conjugates were screened for anti-inflammatory, analgesic and antimicrobial properties. Some of the conjugates showed promising biological observations with a potency comparable with the standard references. The variations in biological properties concerning different amino acids and protecting groups are interesting observations. Effects of the synthesized conjugates on splenocytes and the production of nitric oxide by lipopolysaccharide-stimulated peritoneal macrophages are correlated with the observed anti-inflammatory properties. We have also established the safety profile of the most active conjugates. Robust 2D-QSAR studies supported and validated biological data.

Effect of curcumin derivatives on hen egg white lysozyme amyloid fibrillation and their interaction study by spectroscopic methods

Two novel Boc-L-isoleucine-functionalized curcumin derivatives have been synthesized and characterized, which exhibited enhanced solubility in water compared with the natural curcumin. The solubility could reach 2.12mg/mL for the monosubstituted compound and 3.05mg/mL for the disubstituted compound, respectively. Their anti-amyloidogenic capacity on the model protein, hen egg white lysozyme (HEWL), was examined in aqueous solution. ThT fluorescence assay showed that the operation concentration was only 0.5mM when the inhibition ratio was above 70%. Meanwhile, the inhibitory capacity of monosubstituted curcumin derivative on the formation of HEWL amyloid fibrils was found to be superior to that of disubstituted derivative, suggesting that the phenolic hydroxyl group might contribute to the anti-amyloidogenic activity. Interaction study showed that both curcumin derivatives could bind with HEWL near tryptophan residues and form new ground-state complex before HEWL self-assemblies into amyloid fibrils and thus inhibits the formation of amyloid fibrils. Both of the two cucumin derivatives have displayed low cytotoxicity with HeLa cell.

In vitro and in silico molecular interaction of multiphase nanoparticles containing inositol hexaphosphate and jacalin: Therapeutic potential against colon cancer cells (HCT-15)

Inositol hexaphosphate (IP6) is a natural constituent found in almost all cereals and legumes. It is known to cause numerous antiangiogenic manifestations. Notwithstanding its great potential, it is underutilized due to the chelation and rapid excretion from the body. Jacalin is another natural constituent obtained from seeds of jackfruit and can target disaccharides overexpressed in tumor cells. The current study was in-quested to develop and evaluate a surface-modified gold nanoparticulate system containing IP6 and jacalin which may maximize the apoptotic effect of IP6 against HCT-15 cell lines. IP6 loaded jacalin-pectin-gold nanoparticles (IJP-GNPs) were developed through reduction followed by incubation method. The developed formulation was tested for various in vitro and in silico studies to investigate its potential. HCT-15 cells when exposed to IJP-GNP resulted in significant apoptotic effects in dose as well as time-dependent manner, as measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, micronucleus, and reactive oxygen species assay. IJP-GNP displayed cell cycle arrest at the G0/G1 phase. To further explore the mechanism of chemoprevention, in silico studies were performed. The docking results revealed that the interactive behavior of IP6, P-GNP, and jacalin could target and inhibit the tumor formation activity, supported by in vitro studies. Taken together, all the findings suggested that IP6 loaded nanoparticles may increase the hope of future drug delivery strategy for targeting colon cancer.

Plant antimicrobial polyphenols as potential natural food preservatives

BACKGROUND

The growing demand for natural food preservatives in the last decade has promoted investigations on their application for preserving perishable foods. In this context, the present review is focused on discussing the prospective application of plant extracts containing phenolics or isolated plant phenolics as natural antimicrobials in foods. Plant essential oils are outside the scope of this review since utilization of their antimicrobial activity for food preservation has been extensively reviewed.

RESULTS

Although the exact antimicrobial mechanisms of action of phenolic compounds are not yet fully understood, it is commonly acknowledged that they have diverse sites of action at the cellular level. Antimicrobial phenolics can be added directly to the formulation of perishable food products or incorporated into food-contact materials to release them in the immediate zone of perishable foods. Edible coatings or active food packaging materials can thus be used as carriers of plant bioactive compounds.

CONCLUSION

These materials could be an interesting delivery system to improve the stability of phenolics in foods and to improve the shelf life of perishable foods. This review will thus provide an overview of current knowledge of the antimicrobial activity of phenolic-rich plant extracts and of the promises and limits of their exploitation for the preservation of perishable foods. © 2018 Society of Chemical Industry.

Atorvastatin Downregulates In Vitro Methyl Methanesulfonate and Cyclophosphamide Alkylation-Mediated Cellular and DNA Injuries

Statins are 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, and this class of drugs has been studied as protective agents against DNA damages. Alkylating agents (AAs) are able to induce alkylation in macromolecules, causing DNA damage, as DNA methylation. Our objective was to evaluate atorvastatin (AVA) antimutagenic, cytoprotective, and antigenotoxic potentials against DNA lesions caused by AA. AVA chemopreventive ability was evaluated using antimutagenicity assays (Salmonella/microsome assay), cytotoxicity, cell cycle, and genotoxicity assays in HepG2 cells. The cells were cotreated with AVA and the AA methyl methanesulfonate (MMS) or cyclophosphamide (CPA). Our datum showed that AVA reduces the alkylation-mediated DNA damage in different in vitro experimental models. Cytoprotection of AVA at low doses (0.1–1.0 μM) was observed after 24 h of cotreatment with MMS or CPA at their LC₅₀, causing an increase in HepG2 survival rates. After all, AVA at 10 μM and 25 μM had decreased effect in micronucleus formation in HepG2 cells and restored cell cycle alterations induced by MMS and CPA. This study supports the hypothesis that statins can be chemopreventive agents, acting as antimutagenic, antigenotoxic, and cytoprotective components, specifically against alkylating agents of DNA.

Enhancement of Curcumin Bioavailability Via the Prodrug Approach: Challenges and Prospects

Curcumin is a natural product with many interesting pharmacological properties. However, these are offset by the particularly poor biopharmaceutical properties. The oral bioavailability of curcumin in humans is very low, mainly due to low solubility, poor stability, and extensive metabolism. This has led to multiple approaches to improve bioavailability, including administration of curcumin with metabolism inhibitors, formulation into nanoparticles, modification of the curcumin structure, and development of curcumin prodrugs. In this paper, we focus on the pharmacokinetic outcomes of these approaches. Pharmacokinetic parameters of curcumin after release from prodrugs are dependent on the linker between curcumin and the promoiety, and the release itself may depend on the physiological and enzymatic environment at the site of cleavage. This is an area in which more data are required for rational design of improved linkers. Cytotoxicity of curcumin prodrugs seems to correlate well with cellular uptake in vitro, but the in vivo relevance is uncertain. We conclude that improved experimental and theoretical models of absorption of curcumin prodrugs, development of accurate analytical methods for simultaneous measurement of plasma levels of prodrug and released curcumin, and acquisition of more pharmacokinetic data in animal models for dose prediction in humans are required to facilitate movement of curcumin prodrugs into clinical trials.

The effect of the molecular weight of hyaluronic acid on the physicochemical characterization of hyaluronic acid-curcumin conjugates and in vitro evaluation in glioma cells

In this study, a redox-sensitive glioma-targeting micelle system was designed to deliver curcumin (CUR) by conjugating it to hyaluronic acid (HA-s-s-CUR, HSC) via disulfide linkage. The effect of the molecular weight of HA on the physicochemical characteristics of HSC conjugates and their in vitro effects in glioma cells were also explored. These conjugates formed nano-scale micelles (209-926 nm) independently in aqueous solution. The micelles greatly increased the solubility of CUR and improved its stability, which is crucial for harnessing the therapeutic potential of this active molecule. The redox sensitivities of different HSC micelles were measured by using a dynamic light scattering method and in vitro release assay, which showed that the low (50 kDa) and medium molecular weight (200 kDa and 500 kD) HA-based conjugates were sensitive to GSH, whereas higher molecular weights (1000 kDa and 2000 kDa) did not show redox-sensitivity. Increased cytotoxicity and uptake of low and medium molecular weight-modified HSC conjugates by the glioma cells further confirmed that the sensitive micelles are more effective for intracellular drug delivery compared to the high molecular weight-modified HSC conjugates or the plain CUR. In summary, the molecular weight of HA affects the physicochemical attributes of HSC conjugates. Only HSC micelles made with HA molecules less than 500 kDa exhibit redox sensitivity.

Synthesis of water-soluble curcumin derivatives and their inhibition on lysozyme amyloid fibrillation

The potential application of curcumin was heavily limited in biomedicine because of its poor solubility in pure water. To circumvent the detracting feature, two novel water-soluble amino acid modified curcumin derivatives (MLC and DLC) have been synthesized through the condensation reaction between curcumin and N^α-Fmoc-N^ε-Boc-l-lysine. Benefiting from the enhanced solubility of 3.32×10^-2g/mL for MLC and 4.66×10^-2g/mL for DLC, the inhibition effects of the as-prepared derivatives on the amyloid fibrillation of lysozyme (HEWL) were investigated detaily in water solution. The obtained results showed that the amyloid fibrillation of HEWL was inhibited to a great extent when the concentrations of MLC and DLC reach to 20.139mM and 49.622mM, respectively. The fluorescence quenching upon the addition of curcumin to HEWL provide a support for static and dynamic recombination quenching process. The binding driving force was assigned to classical hydrophobic interaction between curcumin derivatives and HEWL. In addition, UV-Vis absorption and circular dichroism (CD) spectra confirmed the change of the conformation of HEWL.

Turmeric Extract Rescues Ethanol-Induced Developmental Defect in the Zebrafish Model for Fetal Alcohol Spectrum Disorder (FASD)

Prenatal ethanol exposure causes the most frequent preventable birth disorder, fetal alcohol spectrum disorder (FASD). The effect of turmeric extracts in rescuing an ethanol-induced developmental defect using zebrafish as a model was determined. Ethanol-induced oxidative stress is one of the major mechanisms underlying FASD. We hypothesize that antioxidant inducing properties of turmeric may alleviate ethanol-induced defects. Curcuminoid content of the turmeric powder extract (5 mg/mL turmeric in ethanol) was determined by UPLC and found to contain Curcumin (124.1 ± 0.2 μg/mL), Desmethoxycurcumin (43.4 ± 0.1 μg/mL), and Bisdemethoxycurcumin (36.6 ± 0.1 μg/mL). Zebrafish embryos were treated with 100 mM (0.6% v/v) ethanol during gastrulation through organogenesis (2 to 48 h postfertilization (hpf)) and supplemented with turmeric extract to obtain total curcuminoid concentrations of 0, 1.16, 1.72, or 2.32 μM. Turmeric supplementation showed significant rescue of the body length at 72 hpf compared to ethanol-treated embryos. The mechanism underlying the rescue remains to be determined.

Therapeutic potential of novel formulated forms of curcumin in the treatment of breast cancer by the targeting of cellular and physiological dysregulated pathways

Breast cancer is among the most important causes of cancer related death in women. There is a need for novel agents for targeting key signaling pathways to either improve the efficacy of the current therapy, or reduce toxicity. There is some evidence that curcumin may have antitumor activity in breast cancer. Several clinical trials have investigated its activity in patients with breast cancer, including a recent trial in breast cancer patients receiving radiotherapy, in whom it was shown that curcumin reduced the severity of radiation dermatitis, although it is associated with low bioavailability. Several approaches have been developed to increase its absorption rate (e.g., nano crystals, liposomes, polymers, and micelles) and co-delivery of curcumin with adjuvants as well as different conjugation to enhance its bioavailability. In particular, micro-emulsions is an option for transdermal curcumin delivery, which has been reported to increase its absorption. Lipid-based nano-micelles is another approach to enhance curcumin absorption via gastrointestinal tract, while polymer-based nano-formulations (e.g., poly D, L-lactic-co-glycolic [PLGA]) allows the release of curcumin at a sustained level. This review summarizes the current data of the therapeutic potential of novel formulations of curcumin with particular emphasis on recent preclinical and clinical studies in the treatment of breast cancer.

Curcumin as a multifaceted compound against human papilloma virus infection and cervical cancers: A review of chemistry, cellular, molecular, and preclinical features

Curcumin, the bioactive polyphenolic ingredient of turmeric, has been extensively studied for its effects on human papilloma virus (HPV) infection as well as primary and malignant squamous cervical cancers. HPV infections, especially those related to HPV 16 and 18 types, have been established as the leading cause of cervical cancer; however, there are also additional contributory factors involved in the etiopathogenesis of cervical cancers. Curcumin has emerged as having promising chemopreventive and anticancer effects against both HPV-related and nonrelated cervical cancers. In this review, we first discuss the biological relevance of curcumin and both its pharmacological effects and pharmaceutical considerations from a chemical point of view. Next, the signaling pathways that are modulated by curcumin and are relevant to the elimination of HPV infection and treatment of cervical cancer are discussed. We also present counter arguments regarding the effects of curcumin on signaling pathways and molecular markers dysregulated by benzo(a)pyrene (Bap), a carcinogen found in pathological cervical lesions of women who smoke frequently, and estradiol, as two important risk factors involved in persistent HPV-infection and cervical cancer. Finally, various strategies to enhance the pharmacological activity and pharmacokinetic characteristics of curcumin are discussed with examples of studies in experimental models of cervical cancer. © 2016 BioFactors, 43(3):331-346, 2017.

Biological activities of curcuminoids, other biomolecules from turmeric and their derivatives - A review

In recent years, several drugs have been developed deriving from traditional products and current drug research is actively investigating the possible therapeutic roles of many Ayruvedic and Traditional Indian medicinal therapies. Among those being investigated is Turmeric. Its most important active ingredient is curcuminoids. Curcuminoids are phenolic compounds commonly used as a spice, pigment and additive also utilized as a therapeutic agent used in several foods. Comprehensive research over the last century has revealed several important functions of curcuminoids. Various preclinical cell culture and animals studies suggest that curcuminoids have extensive biological activity as an antioxidant, neuroprotective, antitumor, anti-inflammatory, anti-acidogenic, radioprotective and arthritis. Different clinical trials also suggest a potential therapeutic role for curcuminoids in numerous chronic diseases such as colon cancer, lung cancer, breast cancer, inflammatory bowel diseases. The aim of this review is to summarize the chemistry, analog, metal complex, formulations of curcuminoids and their biological activities.

New bis(hydroxymethyl) alkanoate curcuminoid derivatives exhibit activity against triple-negative breast cancer in vitro and in vivo

Novel bis(hydroxymethyl) alkanoate curcuminoid derivatives were designed, synthesized and screened for in vitro antiproliferative and in vivo antitumor activity. Selected new compound 9a and curcumin were further evaluated for inhibitory activity against ER⁺/PR⁺ breast cancer (MCF-7, T47D), HER 2⁺ breast cancer (SKBR3, BT474, and MDA-MB-457) and triple negative breast cancer (TNBC) (HS-578T, MDA-MB-157, and MDA-MB-468) cell lines. In addition, compound 9a was evaluated in the MDA-MB-231 xenograft nude mice model. Compound 9a exhibited greater inhibitory activity than curcumin against TNBC cells and also demonstrated significant inhibitory activity against doxorubicin-resistant MDA-MB-231 cells, with ten-fold higher potency than curcumin. Furthermore, when evaluated against the MDA-MB-231 xenograft nude mice model, compound 9a alone was ten-fold more potent than curcumin. Moreover, synergistic activity was observed when 9a was used in combination with doxorubicin against MDA-MB-231 breast cancer cells.

Modulatory effects of Cassia fistula fruits against free radicals and genotoxicity of mutagens

Cassia fistula L. (Fabaceae) fruits are highly recommended in folklore medicine for curing various ailments. In the current study, methanol (CaFM), hexane (CaFH), chloroform (CaFCl), ethyl acetate (CaFE), butanol (CaFB) and aqueous (CaFA) fractions of C. fistula fruits were investigated for their potential to inhibit the genotoxicity of mutagens and free radicals. The antimutagenicity of fractions was evaluated against the reactive carcinogenic ester generating mutagen, 2-aminofluorene (2-AF) and frame-shift mutation inducing mutagen, 4-nitro-o-phenylenediamine (NPD) in Ames Salmonella typhimurium TA98 tester strain. Among the fractions, CaFE showed strongest protective effect against the mutagenicity of both S9-dependent and direct-acting mutagen with an inhibitory percentage of 81% and 64% at the concentration of 1 × 10³ and 2.5 × 10³ respectively. All the fractions were analyzed for free radical scavenging activity using DPPH, nitric oxide, lipid peroxidation and superoxide anion assays. CaFE fraction showed maximum antioxidant activity in comparison to other fractions with an IC₅₀ of 97.01, 172.36, 144 and 264.79 μg/ml respectively. High performance liquid chromatography showed the presence of catechin, epicatechin and umbelliferone in appreciable amount which may account for its efficacy in combating free radicals and also showed protective effect against the mutagenicity of S9-dependent mutagen, 2-AF.

Biological evaluation and molecular docking studies of new curcuminoid derivatives: Synthesis and characterization

In the present study, three series of dimethylamino curcuminoids viz. 4-phenylaminomethyl curcumin (3a-d), arylidene curcumin (3e) and pyrazole curcumin (3f-i) derivatives have been synthesized and studied for their in vitro anti-inflammatory, antioxidant and antibacterial activities. Synthesized dimethylamino curcuminoid derivatives namely 3d, 3e, 3h and 3i have shown potent anti-inflammatory properties than parent curcumin. Molecular docking interactions of dimethylamino curcuminoids derivatives against cyclooxygenase enzymes (COX-1 and COX-2) were studied.

In Silico Profiling of the Potentiality of Curcumin and Conventional Drugs for CagA Oncoprotein Inactivation

The oncoprotein cytotoxic associated gene A (CagA) of Helicobacter pylori plays a pivotal role in the development of gastric cancer, so it has been an important target for anti-H. pylori drugs. Conventional drugs are currently being implemented against H. pylori. The inhibitory role of plant metabolites like curcumin against H. pylori is still a major scientific challenge. Curcumin may represent a novel promising drug against H. pylori infection without producing side effects. In the present study, a comparative analysis between curcumin and conventional drugs (clarithromycin, amoxicillin, pantoprazole, and metronidazole) was carried out using databases to investigate the potential of curcumin against H. pylori targeting the CagA oncoprotein. Curcumin was filtered using Lipinski's rule of five and the druglikeness property for evaluation of pharmacological properties. Subsequently, molecular docking was employed to determine the binding affinities of curcumin and conventional drugs to the CagA oncoprotein. According to the results obtained from FireDock, the binding energy of curcumin was higher than those of amoxicillin, pantoprazole, and metronidazole, except for clarithromycin, which had the highest binding energy. Accordingly, curcumin may become a promising lead compound against CagA+ H. pylori infection.

Synthesis and biological evaluation of new symmetric curcumin derivatives

A series of novel curcumin bisacetamides aiming of enriching their biological activities have been synthesized. The synthesized compounds were screened for their in vitro antioxidant, anti-inflammatory and cytotoxic activities. All the compounds exhibited potent to good anti-inflammatory, antioxidant and noteworthy cytotoxic activities.

Curcumin-incorporated albumin nanoparticles and its tumor image

Albumin is an ideal carrier for hydrophobic drugs. This paper reports a facile route to develop human serum albumin (HSA)-curcumin (CCM) nanoparticles, in which β-mercaptoethanol (β-ME) acted as an inducer and CCM acted as a bridge. Fluorescence quenching and conformational changes in HSA-CCM nanoparticles occurred during assembly. Disulfide bonds and hydrophobic interactions may play a key role in assembly. HSA-CCM nanoparticles were about 130 nm in size, and the solubility of CCM increased by more than 500 times. The HSA-CCM nanoparticles could accumulate at the cytoplasm of tumor cells and target the tumor tissues. Therefore, HSA nanoparticles fabricated by β-ME denaturation are promising nanocarriers for hydrophobic substances from chemotherapy drugs to imaging probes.

Hepatoprotective agent tethered isoniazid for the treatment of drug-induced hepatotoxicity: Synthesis, biochemical and histopathological evaluation

The aim of the study was to investigate the protective effect of isoniazid–curcumin conjugate (INH–CRM) in INH-induced hepatic injury by biochemical analysis and histology examination of liver in Wistar rats. The biochemical analysis included determination of the levels of plasma cholesterol, triglycerides (TG), albumin content, and lipid peroxidation (MDA). INH–CRM administration resulted in a significant decrease in plasma cholesterol, TG, and MDA levels in the liver tissue homogenate with an elevation in albumin level indicating its hepatoprotective activity. Histology of the liver further confirmed the reduction in hepatic injury. The hepatoprotective with INH–CRM can be attributed to the antioxidant activity of curcumin. The conjugate probably stabilizes the curcumin molecule, preventing its presystemic metabolism thereby enhancing its bioavailability and therefore, its hepatoprotective activity. Thus, the novel INH–CRM has the potential to alleviate INH-induced liver toxicity in antitubercular treatment.

Antimutagenic compounds and their possible mechanisms of action

Mutagenicity refers to the induction of permanent changes in the DNA sequence of an organism, which may result in a heritable change in the characteristics of living systems. Antimutagenic agents are able to counteract the effects of mutagens. This group of agents includes both natural and synthetic compounds. Based on their mechanism of action among antimutagens, several classes of compounds may be distinguished. These are compounds with antioxidant activity; compounds that inhibit the activation of mutagens; blocking agents; as well as compounds characterized with several modes of action. It was reported previously that several antitumor compounds act through the antimutagenic mechanism. Hence, searching for antimutagenic compounds represents a rapidly expanding field of cancer research. It may be observed that, in recent years, many publications were focused on the screening of both natural and synthetic compounds for their beneficial muta/antimutagenicity profile. Thus, the present review attempts to give a brief outline on substances presenting antimutagenic potency and their possible mechanism of action. Additionally, in the present paper, a screening strategy for mutagenicity testing was presented and the characteristics of the most widely used antimutagenicity assays were described.

Curcumin nanoformulations: a review of pharmaceutical properties and preclinical studies and clinical data related to cancer treatment

Curcumin, a natural yellow phenolic compound, is present in many kinds of herbs, particularly in Curcuma longa Linn. (turmeric). It is a natural antioxidant and has shown many pharmacological activities such as anti-inflammatory, anti-microbial, anti-cancer, and anti-Alzheimer in both preclinical and clinical studies. Moreover, curcumin has hepatoprotective, nephroprotective, cardioprotective, neuroprotective, hypoglycemic, antirheumatic, and antidiabetic activities and it also suppresses thrombosis and protects against myocardial infarction. Particularly, curcumin has demonstrated efficacy as an anticancer agent, but a limiting factor is its extremely low aqueous solubility which hampers its use as therapeutic agent. Therefore, many technologies have been developed and applied to overcome this limitation. In this review, we summarize the recent works on the design and development of nano-sized delivery systems for curcumin, including liposomes, polymeric nanoparticles and micelles, conjugates, peptide carriers, cyclodextrins, solid dispersions, lipid nanoparticles and emulsions. Efficacy studies of curcumin nanoformulations using cancer cell lines and in vivo models as well as up-to-date human clinical trials are also discussed.