Comparative antioxidant activities of curcumin and its demethoxy and hydrogenated derivatives

A Natural Degradant of Curcumin, Feruloylacetone Inhibits Cell Proliferation via Inducing Cell Cycle Arrest and a Mitochondrial Apoptotic Pathway in HCT116 Colon Cancer Cells

Feruloylacetone (FER) is a natural degradant of curcumin after heating, which structurally reserves some functional groups of curcumin. It is not as widely discussed as its original counterpart has been previously; and in this study, its anticancer efficacy is investigated. This study focuses on the suppressive effect of FER on colon cancer, as the efficacious effect of curcumin on this typical cancer type has been well evidenced. In addition, demethoxy-feruloylacetone (DFER) was applied to compare the effect that might be brought on by the structural differences of the methoxy group. It was revealed that both FER and DFER inhibited the proliferation of HCT116 cells, possibly via suppression of the phosphorylated mTOR/STAT3 pathway. Notably, FER could significantly repress both the STAT3 phosphorylation and protein levels. Furthermore, both samples showed capability of arresting HCT116 cells at the G2/M phase via the activation of p53/p21 and the upregulation of cyclin-B. In addition, ROS elevation and changes in mitochondrial membrane potential were revealed, as indicated by p-atm elevation. The apoptotic rate rose to 36.9 and 32.2% after being treated by FER and DFER, respectively. In summary, both compounds exhibited an anticancer effect, and FER showed a greater proapoptotic effect, possibly due to the presence of the methoxy group on the aromatic ring.

The Anti-Cancer Effect of Four Curcumin Analogues on Human Glioma Cells

Purpose

Glioblastoma multiforme (GBM) is the primary aggressive malignancy of the brain with poor outcome. Curcumin analogues are polyphenolic compounds as the bioactive substances extracted from turmeric. This study aims to investigate the anti-cancer effects of four curcumin analogues. Furthermore, the molecular mechanisms of dimethoxycurcumin in human gliomas were analyzed by Western blot.

Materials and Methods

Human LN229 and GBM8401 glioma cells were treated by four curcumin analogues with different number of methoxy groups. The cell viability, cell cycle, apoptosis, proliferation and ROS production of human gliomas were analyzed by flow cytometry. Moreover, the effects of four curcumin analogues on tumorigenesis of gliomas were conducted by wound healing assay and colony formation assay. Furthermore, the molecular mechanisms of dimethoxycurcumin in human gliomas were analyzed by Western blot.

Results

Our data showed that four different curcumin analogues including curcumin, bisdemethoxycurcumin, demethoxycurcumin, and dimethoxycurcumin promote sub-G1 phase, G2/M arrest, apoptosis, and ROS production in human glioma cells. Moreover, dimethoxycurcumin suppressed cell viability, migration, and colony formation, induction of sub-G1, G2/M arrest, apoptosis, and ROS production in glioma cells. Moreover, the mechanism of dimethoxycurcumin is ROS production to increase LC3B-II expression to induce autophagy. Furthermore, dimethoxycurcumin suppressed apoptotic marker, BCL-2 to promote apoptosis in LN229 and GBM8401 glioma cells.

Conclusion

Our study found that dimethoxycurcumin induced apoptosis, autophagy, ROS production and suppressed cell viability in human gliomas. Dimethoxycurcumin might be a potential therapeutic candidate in human glioma cells.

Curcumin Modulates Nitrosative Stress, Inflammation, and DNA Damage and Protects against Ochratoxin A-Induced Hepatotoxicity and Nephrotoxicity in Rats

Ochratoxin A (OTA) is a fungal toxin of critical concern for food safety both for human health and several animal species, also representing a cancer threat to humans. Curcumin (CURC) is a natural polyphenol that has anti-apoptotic, anti-inflammatory, and antioxidant effects. The aim of this study was to investigate the cytoprotective effect of CURC against OTA-induced nephrotoxicity and hepatotoxicity through the study of the nitrosative stress, pro-inflammatory cytokines, and deoxyribonucleic acid (DNA) damage. Sprague Dawley rats were daily treated with CURC (100 mg/kg b.w.), OTA (0.5 mg/kg b.w), or CURC with OTA by oral gavage for 14 days. Our results demonstrated that OTA exposure was associated with significant increase of pro-inflammatory and DNA oxidative-damage biomarkers. Moreover, OTA induced the inducible nitric oxide synthase, (iNOS) resulting in increased nitric oxide (NO) levels both in kidney and liver. The co-treatment OTA + CURC counteracted the harmful effects of chronic OTA treatment by regulating inflammation, reducing NO levels and oxidative DNA damage in kidney and liver tissues. Histology revealed that OTA + CURC treatment determinates mainly an Iba1+ macrophagic infiltration with fewer CD3+ T-lymphocytes in the tissues. In conclusion, we evidenced that CURC exerted cytoprotective and antioxidant activities against OTA-induced toxicity in rats.

Curcumin and Piperine in COVID-19: A Promising Duo to the Rescue?

COVID-19 is now pandemic throughout the world, and scientists are searching for effective therapies to prevent or treat the disease. The combination of curcumin and piperine is a potential option for the management of COVID-19 based on several mechanisms including antiviral, anti-inflammatory, immunomodulatory, antifibrotic, and antioxidant effects. Here, we describe the probable mechanism of curcumin-piperine against COVID-19. Administration of curcumin-piperine combination appears as a potential strategy to counterbalance the pathophysiological features of COVID-19 including inflammation. The optimal dose and duration of curcumin-piperine supplementation should be determined in the future.

Pharmacokinetics-Driven Evaluation of the Antioxidant Activity of Curcuminoids and Their Major Reduced Metabolites-A Medicinal Chemistry Approach

Curcuminoids are the main bioactive components of the well-known Asian spice and traditional medicine turmeric. Curcuminoids have poor chemical stability and bioavailability; in vivo they are rapidly metabolized to a set of bioreduced derivatives and/or glucuronide and sulfate conjugates. The reduced curcuminoid metabolites were also reported to exert various bioactivities in vitro and in vivo. In this work, we aimed to perform a comparative evaluation of curcuminoids and their hydrogenated metabolites from a medicinal chemistry point of view, by determining a set of key pharmacokinetic parameters and evaluating antioxidant potential in relation to such properties.Reduced metabolites were prepared from curcumin and demethoxycurcumin through continuous-flow hydrogenation. As selected pharmacokinetic parameters, kinetic solubility, chemical stability, metabolic stability in human liver microsomes, and parallel artificial membrane permeability assay (PAMPA)-based gastrointestinal and blood-brain barrier permeability were determined. Experimentally determined logP for hydrocurcumins in octanol-water and toluene-water systems provided valuable data on the tendency for intramolecular hydrogen bonding by these compounds. Drug likeness of the compounds were further evaluated by a in silico calculations. Antioxidant properties in diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and oxygen radical absorbance capacity (ORAC) assays were comparatively evaluated through the determination of ligand lipophilic efficiency (LLE). Our results showed dramatically increased water solubility and chemical stability for the reduced metabolites as compared to their corresponding parent compound. Hexahydrocurcumin was found the best candidate for drug development based on a complex pharmacokinetical comparison and high LLE values for its antioxidant properties. Development of tetrahydrocurcumin and tetrahydro-demethoxycurcumin would be limited by their very poor metabolic stability, therefore such an effort would rely on formulations bypassing first-pass metabolism.

Dietary bisdemethoxycurcumin supplementation attenuates lipopolysaccharide-induced damages on intestinal redox potential and redox status of broilers

This study was conducted to investigate the beneficial effects of bisdemethoxycurcumin (BDC) on growth performance, glutathione (GSH) redox potential, antioxidant enzyme defense, and gene expression in lipopolysaccharide (LPS)-challenged broilers. A total of 320, male, 1-day-old broilers were randomly assigned to 4 treatment groups including 8 replicates with 10 birds per cage in a 2 × 2 factorial arrangement: BDC supplementation (a basal diet with 0 or 150 mg/kg BDC) and LPS challenge (intraperitoneal injection of 1 mg/kg body weight saline or LPS at 16, 18, and 20 d of age). Results showed that dietary BDC supplementation prevented the LPS-induced decrease in ADG of broilers (P < 0.05). Compared to the saline-challenged group, LPS-challenged broilers showed higher jejunal and ileal malondialdehyde (MDA), protein carbonyl (PC), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) contents (P < 0.05). Dietary BDC supplementation alleviated LPS-induced increases in jejunal 8-OHdG, ileal MDA, and PC contents (P < 0.05). LPS challenge impaired the small intestinal antioxidant system, as evident by the decreases of GSH and total thiol contents, as well as superoxide dismutase (SOD), glutathione peroxidase, glutathione reductase (GR), and glutathione S-transferase (GST) activities. On the other hand, LPS challenge also increased GSH redox potential and oxidized glutathione (GSSG) contents (P < 0.05). Dietary BDC supplementation increased jejunal and ileal GSH contents, SOD activities, jejunal GR activity, and ileal GST activity, while it decreased jejunal and ileal redox potential, and jejunal GSSG contents (P < 0.05). Dietary BDC supplementation significantly alleviated the downregulation of mRNA expression levels of jejunal and ileal copper and zinc superoxide dismutase, catalytic subunit of γ-glutamylcysteine ligase, nuclear factor erythroid-2-related factor 2, heme oxygenase 1, NAD(P)H quinone oxidoreductase 1, and jejunal catalase and GR induced by LPS challenge (P < 0.05). In conclusion, BDC demonstrated favorable protection against LPS-induced small intestinal oxidative damages, as indicated by the improved growth performance, decreased GSH redox potential, enhanced antioxidant enzyme activities, and upregulated antioxidant-related gene expression.

Design of New Improved Curcumin Derivatives to Multi-targets of Cancer and Inflammation

BACKGROUND

Curcumin is a major active principle of Curcuma longa. There are more than 1700 citations in the Medline, reflecting various biological effects of curcumin. Most of these biological activities are associated with the antioxidant, anti-inflammatory and antitumor activity of the molecule. Several reports suggest various targets of natural curcumin that include growth factors, growth factor receptor, cytokines, enzymes and gene regulators of apoptosis. This review focuses on the improved curcumin derivatives that target the cancer and inflammation.

METHODOLOGY

In this present review, we explored the anticancer drugs with curcumin-based drugs under pre-clinical and clinical studies with critical examination. Based on the strong scientific reports of patentable and non-patented literature survey, we have investigated the mode of the interactions of curcumin-based molecules with the target molecules.

RESULTS

Advanced studies have added new dimensions of the molecular response of cancer cells to curcumin at the genomic level. However, poor bioavailability of the molecule seems to be the major limitation of the curcumin. Several researchers have been involved to improve the curcumin derivatives to overcome this limitation. Sufficient data of clinical trials to various cancers that include multiple myeloma, pancreatic cancer and colon cancer, have also been discussed.

CONCLUSION

The detailed analysis of the structure-activity relationship (SAR) and common synthesis of curcumin-based derivatives have been discussed in the review. Utilising the predictions of in silico coupled with validation reports of in vitro and in vivo studies have concluded many targets for curcumin. Among them, cancer-related inflammation genes regulating curcumin-based molecules are a very promising target to overcome hurdles in the multimodality therapy of cancer.

Inhibitory Effect of Hexahydrocurcumin on Memory Impairment and Amyloidogenesis in Dexamethasone-Treated Mice

A high dose of dexamethasone induces neurodegeneration by initiating the inflammatory processes that lead to neural apoptosis. A dexamethasone administration model induces overproduction of amyloid-β (Aβ) and tau protein hyperphosphorylation and shows abnormalities of cholinergic function similar to Alzheimer's disease (AD). This study aimed to investigate the protective effect of hexahydrocurcumin on the brain of dexamethasone-induced mice. The results showed that hexahydrocurcumin and donepezil attenuated the levels of amyloid precursor protein and β-secretase mRNA by reverse transcription polymerase chain reaction, decreased the expression of hyperphosphorylated tau, and improved synaptic function. Moreover, we found that hexahydrocurcumin treatment could decrease interleukin-6 levels by attenuating p65 of nuclear factor kappa-light-chain-enhancer (NF-κB) of activated beta cells. In addition, hexahydrocurcumin also decreased oxidative stress, as demonstrated by the expression of 4-hydroxynonenal and thereby prevented apoptosis. Therefore, our finding suggests that hexahydrocurcumin prevents dexamethasone-induced AD-like pathology and improves memory impairment.

Molecular targets for the management of cancer using Curcuma longa Linn. phytoconstituents: A Review

Medicinal plants are being used for therapeutic purposes since the dawn of human civilization. The therapeutic efficacy of medicinal plants is due to the presence of wide range phytochemical constituents or secondary metabolites. The medicinal plants are traditionally used for several types of ailments. Even in those pathological conditions where other methods of treatment fail to work. Curcuma longa Linn is very common ingredient used as spice in foods as preservative and coloring material in different part of the world. It has been used as a home remedy for a variety of diseases. Curcuma longa and its isolated constituent curcumin are widely evaluated for anticancer activity. Curcumin possesses broad remedial potential due to its multi-targeting effect against many different carcinoma including leukemia, genitourinary cancers, gastrointestinal cancers and breast cancer etc. Hence, Curcumin has potential for the development of new medicine for the treatment of several diseases.

Comparation of Anti-Inflammatory and Antioxidantactivities of Curcumin, Tetrahydrocurcuminand Octahydrocurcuminin LPS-Stimulated RAW264.7 Macrophages

Curcumin (CUR) possesses pronounced anti-inflammatory and antioxidant activities. Generally, the clinical application of CUR is restricted due to its apparent unstability and poor absorption, and the biological activities of CUR may be closely associated with its metabolites. Tetrahydrocurcumin (THC) and octahydrocurcumin (OHC) are two major hydrogenated metabolites of CUR with appreciable biological potentials. Here, we comparatively explored the anti-inflammatory and antioxidant activities of CUR, THC, and OHC in lipopolysaccharide- (LPS-) induced RAW264.7 macrophages. The results revealed that CUR, THC, and OHC dose-dependently inhibited the generation of NO and MCP-1 as well as the gene expression of MCP-1 and iNOS. Additionally, CUR, THC, and OHC significantly inhibited NF-κB activation and p38MAPK and ERK phosphorylation, while substantially upregulated the Nrf2 target gene expression (HO-1, NQO-1, GCLC, and GCLM). Nevertheless, zinc protoporphyrin (ZnPP), a typical HO-1 inhibitor, significantly reversed the alleviative effect of CUR, THC, and OHC on LPS-stimulated ROS generation. These results demonstrated that CUR, THC, and OHC exerted beneficial effect on LPS-stimulated inflammatory and oxidative responses, at least partially, through inhibiting the NF-κB and MAPKs pathways and activating Nrf2-regulated antioxidant gene expression. Particularly, THC and OHC might exert superior antioxidant and anti-inflammatory activities to CUR in LPS-stimulated RAW264.7 cells, which can be further explored to be a promising novel effective agent for inflammatory treatment.

Curcumin protects radiation-induced liver damage in rats through the NF-κB signaling pathway

BACKGROUND

Curcumin has been demonstrated to exert anti-oxidant, anti-fibrotic, anti-inflammatory, and anti-cancer activities. This study was conducted to observe the effect and inner mechanism of curcumin in rats with radiation-induced liver damage (RILD).

METHODS

Thirty SD rats were classified into Control, Radiation group and Curcumin (Cur) + Radiation group (n = 10 in each group). The changes in body weight of the rats were observed on the 3rd, 7th and 14th days after the treatment with curcumin. On the 14th day post treatment, the heart blood of the rats was drawn for measurement of liver function indices including total protein (TP), alanine aminotransfetase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) as well as aspartate aminotransfetase (AST). Subsequently, the rats were euthanized and liver tissues were taken to observe liver morphological changes using hematoxylin-eosin (HE), and to analyze apoptosis condition using transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) assays. Meanwhile, the oxidative stress level in liver tissue homogenate was determined by biochemical analysis. The expression of nuclear factor kappa B (NF-κB) pathway-associated and apoptosis-associated proteins was detected using Western blot analysis, and the expression levels of inflammatory factors were measured by Enzyme-linked immunosorbent assay (ELISA).

RESULTS

The reduced body weight was observed in rats of the Radiation group compared to the Control and Cur + Radiation groups on day 14. In the Radiation group, hepatic cell edema and inflammatory cell infiltration could be visible under the light microscope, and the hepatocytes presented with vacuolar degeneration. In the Cur + Radiation group, the hepatocytes swelled under the microscope, but the pathological changes were alleviated in comparison with the Radiation group. RILD rats with curcumin treatment presented with decreased ALT, AST, ALP, LDH, and maleicdialdehyde (MDA) levels, and elevated TP, superoxide dismutase (SOD), caspase activated DNase (CAD) and glutathione (GSH) levels. Apoptosis and inflammation in rats with RILD were up-regulated, and the NF-κB pathway was activated, but they were reversed after continuously intragastric administration of curcumin for 14 days.

CONCLUSION

Our study highlights that curcumin treatment reduces the liver damage caused by radiation through the inhibition of the NF-κB pathway.

Comparative Study of Curcumin and Its Hydrogenated Metabolites, Tetrahydrocurcumin, Hexahydrocurcumin, and Octahydrocurcumin, on Melanogenesis in B16F10 and MNT-1 Cells

Curcumin, a bioactive from Curcuma longa, has been shown to possess anti-melanogenic activity previously; however, the effects of its hydrogenated metabolites (HMs)—Tetrahydrocurcumin (THC), Hexahydrocurcumin (HHC), and Octahydrocurcumin (OHC)—on melanogenesis have not been sufficiently explored. We have studied and compared three HMs (THC, HHC, and OHC) with the parent compound, curcumin (PC), on melanin synthesis in B16F10 mouse and MNT-1 human melanoma cells. Our results demonstrated that all the HMs were nontoxic over the concentration range 5–40 µM, while PC was nontoxic at 5 µM but induced toxicity at 20 and 40 µM in B16F10 cells. All three HMs enhanced melanin synthesis, while PC (5 µM) inhibited it. THC (40 µM) significantly stimulated melanin synthesis to a greater degree than HHC and OHC in both B16F10 and MNT-1 cells; the order of melanogenesis stimulation was THC = OHC > HHC in B16F10 mouse cells, while it was THC > HHC > OHC in MNT-1 cells. HMs stimulated melanogenesis by pathways not involving tyrosinase, as neither the intracellular tyrosinase activity nor the protein levels of tyrosinase were affected. In addition, mushroom tyrosinase activity, using L-Dihydroxyphenylalanine (L-DOPA) as the substrate, showed no direct effects of HMs. In summary, our results demonstrate that the HMs enhanced melanogenesis, which establishes that the hydrogenation of the heptadiene moiety of curcumin leads to a loss of its anti-melanogenic activity and instead results in the stimulation of melanogenesis. This stimulation is not further enhanced upon hydrogenation of the β-diketone, which was noted in MNT-1 cells, although the correlation to the number of keto groups differed in B16F10 cells where HHC was the weakest stimulator of melanogenesis. Collectively, THC with both keto groups intact is the best stimulator. Moreover, our results also validate that the electrophilicity of curcumin is necessary for its anti-melanogenic activity, as the non-electrophilic HMs did not inhibit melanogenesis. Furthermore, our results suggest that THC might hold promise as a stimulator of melanogenesis for treatment of hypopigmentation disorders and anti-graying therapies. Future studies to probe the molecular signaling mechanisms and test whether the pro-melanogenic activity of HMs is retained in primary human melanocytes are warranted.

Efficacy and Safety of Tetrahydrocurcuminoids for the Treatment of Canker Sore and Gingivitis

Background

Tetrahydrocurcuminoids (THCs) are among the major metabolites of curcuminoids with a higher bioavailability and physiological stability and exhibit a broad spectrum of therapeutic activities. The objective of this study was to evaluate the efficacy of THCs in patients suffering from canker sore and gingivitis designed as an exploratory clinical trial.

Methods

This is an open label prospective pilot clinical trial carried out at two clinical centers: Noble Hospital, Pune, Maharashtra, and Sri Venkateshwara Hospital, Bangalore, Karnataka in India. Participants were assigned to 21 days of treatment with chewable oral THCs supplement. Patients were instructed to self-administer one chewable tablet containing 100 mg of THCs twice daily for up to 21 days. This clinical trial was registered at a public Clinical Trial Registry in India (http://www.ctri.nic.in). Thirty-one canker sore and twenty-nine gingivitis patients participated in this study. Body mass index, throat numbness/relief, Visual Analog Scale (VAS) pain score, canker sore lesions, gingival appearance, inflammation and bleeding were assessed before and after treatment, at 14 and 21 days. Vital signs and laboratory parameters were assessed for safety.

Results

THCs treatment significantly reduced the reddening at the site, difficulty in chewing, swallowing, and VAS pain score in the canker sore patients. Further, both single and multiple lesions were completely healed. In gingivitis patients, gingival appearance, bleeding, and inflammation were significantly reduced. No adverse effects were observed during the study.

Conclusion

Overall, the findings of this study show that supplementation of THCs for 21 days reduced the pain and prevented the progression of the disease in patients suffering from canker sore and gingivitis without adverse side effects.

Aluminum induced oxidative stress, astrogliosis and cell death in rat astrocytes, is prevented by curcumin

Aluminum (Al) is recognized potent neurotoxic metal, which causes oxidative stress leading to intracellular accumulation of reactive oxygen species (ROS) and neuronal cell death in various neurodegenerative diseases. Among several medicinal plants with beneficial effects on health, curcumin acts as a multi-functional drug with antioxidant activity. Thus, the purpose of the present study was to evaluate the protective effect of curcumin against aluminum induced-oxidative stress and astrocytes death, in vitro ad in vivo. Incubation of cultured rat astrocytes with two concentrations of Al (37 μM and 150 μM) for 1 h provoked a dose-dependent reduction of the number of living cells as evaluated by Fluorescein diacetate and lactate dehydrogenase assay. Al-treated cells exhibited a reduction of both superoxide dismutase (SOD) and catalase activities. Pretreatment of astrocytes with curcumin (81 μM) prevented Al-induced cell death. Regarding in vivo study, rats were exposed acutely during three consecutive days to three different doses of Al (25 mg/kg, 50 mg/kg and 100 mg/kg, i.p injection), together with curcumin treatment (30 mg/kg). For the chronic model, animals were exposed to Al (3 g/l) in drinking water from intrauterine age to 4 months ages, plus curcumin treatment (175 mg/kg). Data showed that both acute and chronic Al intoxication induced an obvious astrogliosis within motor cortex and hippocampus, while, such effects were restored by curcumin. We showed herein that Al was highly toxic, induced astrocytes death. Then, curcumin protected astrocytes against Al-toxicity. The cytoprotective potential of curcumin is initiated by stimulation of endogenous antioxidant system.

Therapeutic role of curcumin and its novel formulations in gynecological cancers

Gynecological cancers are among the leading causes of cancer-associated mortality worldwide. While the number of cases are rising, current therapeutic approaches are not efficient enough. There are considerable side-effects as well as treatment resistant types. In addition, which all make the treatment complicated for afflicted cases. Therefore, in order to improve efficacy of the treatment process and patients’ quality of life, searching for novel adjuvant treatments is highly warranted. Curcumin, a promising natural compound, is endowed with numerous therapeutic potentials including significant anticancer effects. Recently, various investigations have demonstrated the anticancer effects of curcumin and its novel analogues on gynecological cancers. Moreover, novel formulations of curcumin have resulted in further propitious effects. This review discusses these studies and highlights the possible underlying mechanisms of the observed effects.

Curcumin metabolites contribute to the effect of curcumin on ameliorating insulin sensitivity in high-glucose-induced insulin-resistant HepG2 cells

ETHNOPHARMACOLOGICAL EVIDENCE

Curcumin (CUR) is the active ingredient of Traditional Chinese Medicine turmeric (Curcuma longa L.), which has been used for treatment of diabetes in Ayurveda and China. CUR exerts potent anti-insulin-resistant effects in various cell lines. However, previous studies indicated CUR was metabolized extensively in vivo and massively degraded in a medium alkaline buffer solution. The real active component of the anti-insulin-resistant activity of CUR in vitro is not clear.

AIM OF THE STUDY

Our study identified the functional contribution of the metabolites of CUR and the related molecular mechanism in improving insulin sensitivity.

MATERIALS AND METHODS

HPLC and UPLC-QQQ-MS analyses were used to investigate the stability and metabolism of CUR in HepG2 cells. The effect of the metabolic products of CUR on insulin sensitivity was evaluated in high glucose (HG)-induced insulin-resistant HepG2 cells. A network pharmacology approach was used to examine the potential targets of the metabolites, and Western blotting was performed to verify changes in the targets.

RESULTS

CUR was unstable in the cell culture medium, but the prototypes, metabolites and degradation products of CUR coexisted in the HepG2 cell culture experiment. The insulin sensitivity assay demonstrated that CUR and its metabolites enhanced insulin sensitivity in HG-induced insulin-resistant HepG2 cells, but the total degradation products of CUR may not play the major role. Similar to CUR, hexahydrocurcumin (HHC) and octahydrocurcumin (OHC) improved insulin sensitivity by strengthening the PI3K-AKT-GSK3B signal and suppressing the phosphorylation of ERK/JNK in HG-induced insulin-resistant HepG2 cells.

CONCLUSIONS

Metabolites of CUR played a critical role in counteracting insulin resistance in HG-induced HepG2 cells. CUR exerted anti-insulin resistance effect in HepG2 cells in a multi-component, multi-target, and multi-pathway manner.

The Cancer Chemopreventive and Therapeutic Potential of Tetrahydrocurcumin

In recent decades, cancer has been one of the leading causes of death worldwide. Despite advances in understanding the molecular basis of tumorigenesis, diagnosis, and clinical therapies, the discovery and development of effective drugs is an active and vital field in cancer research. Tetrahydrocurcumin is a major curcuminoid metabolite of curcumin, naturally occurring in turmeric. The interest in tetrahydrocurcumin research is increasing because it is superior to curcumin in its solubility in water, chemical stability, bioavailability, and anti-oxidative activity. Many in vitro and in vivo studies have revealed that tetrahydrocurcumin exerts anti-cancer effects through various mechanisms, including modulation of oxidative stress, xenobiotic detoxification, inflammation, proliferation, metastasis, programmed cell death, and immunity. Despite the pharmacological similarities between tetrahydrocurcumin and curcumin, the structure of tetrahydrocurcumin determines its distinct and specific molecular mechanism, thus making it a potential candidate for the prevention and treatment of cancers. However, the utility of tetrahydrocurcumin is yet to be evaluated as only limited pharmacokinetic and oral bioavailability studies have been performed. This review summarizes research on the anti-cancer properties of tetrahydrocurcumin and describes its mechanisms of action.

Nanocurcumin: A Promising Candidate for Therapeutic Applications

Curcuma longa is an important medicinal plant and a spice in Asia. Curcumin (diferuloylmethane) is a hydrophobic bioactive ingredient found in a rhizome of the C. longa. It has drawn immense attention in recent years for its variety of biological and pharmacological action. However, its low water solubility, poor bioavailability, and rapid metabolism represent major drawbacks for its successful therapeutic applications. Hence, researchers have attempted to enhance the biological and pharmacological activity of curcumin and overcome its drawbacks by efficient delivery systems, particularly nanoencapsulation. Research efforts so far and data from the available literature have shown a satisfactory potential of nanorange formulations of curcumin (Nanocurcumin), it increases all the biological and pharmacological benefits of curcumin, which was not significantly possible earlier. For the synthesis of nanocurcumin, an array of techniques has been developed and each technique has its own advantages and individual characteristics. The two most popular and effective techniques are ionic gelation and antisolvent precipitation. So far, many curcumin nanoformulations have been developed to enhance curcumin delivery, thereby overcoming the low therapeutic effects. However, most of the nanoformulation of curcumin remained at the concept level evidence, thus, several questions and challenges still exist to recommend the nanocurcumin as a promising candidate for therapeutic applications. In this review, we discuss the different curcumin nanoformulation and nanocurcumin implications for different therapeutic applications as well as the status of ongoing clinical trials and patents. We also discuss the research gap and future research directions needed to propose curcumin as a promising therapeutic candidate.

Influence of curcumin on glycemic profile, inflammatory markers, and oxidative stress in HIV-infected individuals: A randomized controlled trial

To evaluate the influence of curcumin supplementation on the glycemic profile, inflammatory markers, and oxidative stress in HIV-infected individuals under antiretroviral therapy. This double-blind, crossover, randomized clinical trial was composed of 20 subjects arranged initially into experimental group (n = 10) and placebo group (n = 10) groups, receiving 1,000 mg curcumin/day or microcrystalline cellulose/day, respectively, during a 30-day period and 12-day washout. Subsequently, the groups were switched to follow the crossover design. Fasting glucose and insulin, IL-10, tumor necrosis factor alpha, malonialdehyde, and reduced glutathione were measured. Food consumption was evaluated as a control variable. Descriptive statistics are presented as mean and standard deviation, and inferential analyses were performed from two-way analysis of variance and the magnitude of the effect. No significant improvements were observed in the glycemic, inflammatory, or oxidative stress profiles. Although the mean serum fasting glucose levels and the homeostatic model assessment index presented qualitative improvement in the CG, this result should be interpreted with caution since the observed variation may represent acceptable fluctuation, in addition to the small difference between the means, added to the large variation observed in the standard deviation. Supplementation with curcumin in HIV-infected individuals undergoing antiretroviral therapy and training did not improve the glycemic, inflammatory, or oxidative stress profiles.

Application of curcumin and its derivatives in tumor multidrug resistance

Malignant tumor endangers seriously the health of all mankind. Multidrug resistance (MDR) is one of the main causes of clinical tumor chemotherapy failure. Curcumin (CUR) has not only antitumor activity but also reversing tumor MDR effect. CUR reverses tumor MDR via regulating related signal pathways or corresponding expressed proteins or gene. When combined with chemotherapeutic agents, CUR can be a chemotherapeutic sensitive agent to enhance chemotherapy efficacy and weaken tumor MDR. On the other hand, to improve the MDR reversal effect of CUR, its derivatives have been extensively studied. Therefore, this article mainly focuses on reviewing the application of CUR and its derivatives in MDR and its mechanism of reversing MDR.

Hexahydrocurcumin alleviated blood-brain barrier dysfunction in cerebral ischemia/reperfusion rats

BACKGROUND

Hexahydrocurcumin (HHC), a major metabolite of curcumin, has been reported to have protective effects against ischemic and reperfusion damage. The goal of the present research was to examine whether HHC could alleviate brain damage and ameliorate functional outcomes by diminishing the blood-brain barrier (BBB) damage that follows cerebral ischemia/reperfusion.

METHODS

Middle cerebral artery occlusion was induced for 2 h in rats followed by reperfusion. The rats were divided into three groups: sham-operated, vehicle-treated, and HHC-treated groups. At the onset of reperfusion, the rats were immediately intraperitoneally injected with 40 mg/kg HHC. At 48 h after reperfusion, the rats were evaluated for neurological deficits and TTC staining. At 24 h and 48 h after reperfusion, animals were sacrificed, and their brains were extracted.

RESULTS

Treatment with HHC reduced neurological scores, infarct volume, morphological changes, Evans blue leakage and immunoglobulin G extravasation. Moreover, HHC treatment reduced BBB damage and neutrophil infiltration, downregulated myeloperoxidase, ICAM-1, and VCAM-1, upregulated tight junction proteins (TJPs), and reduced aquaporin 4 expression and brain water content.

CONCLUSION

These results revealed that HHC treatment preserved the BBB from cerebral ischemia/reperfusion injury by regulating TJPs, attenuating neutrophil infiltration, and reducing brain edema formation.

Combined treatment of AT101 and demethoxycurcumin yields an enhanced anti-proliferative effect in human primary glioblastoma cells

PURPOSE

Glioblastoma multiforme (GBM) is a poorly curable disease due to its profound chemoresistance. Despite recent advances in surgery, radiotherapy and chemotherapy, the efficient treatment of GBMs is still a clinical challenge. Beside others, AT101, the R-(-) enantiomer of gossypol, and demethoxycurcumin (DMC), a curcumin-related demethoxy compound derived from Curcuma longa, were considered as possible alternative drugs for GBM therapy.

METHODS

Using different human primary GBM cell cultures in a long-term stimulation in vitro model, the cytotoxic and anti-proliferative effects of single and combined treatment with 5 µM AT101 and 5 µM or 10 µM DMC were investigated. Furthermore, western blots on pAkt and pp44/42 as well as JC-1 staining and real-time RT-PCR were performed to understand the influence of the treatment at the molecular and gene level.

RESULTS

Due to enhanced anti-proliferative effects, we showed that combined therapy with both drugs was superior to a single treatment with AT101 or DMC. Here, by determination of the combination index, a synergism of the combined drugs was detectable. Phosphorylation and thereby activation of the kinases p44/42 and Akt, which are involved in proliferation and survival processes, were inhibited, the mitochondrial membrane potential of the GBM cells was altered, and genes involved in dormancy-associated processes were regulated by the combined treatment strategy.

CONCLUSION

Combined treatment with different drugs might be an option to efficiently overcome chemoresistance of GBM cells in a long-term treatment strategy.

Mechanistic Understanding of Curcumin's Therapeutic Effects in Lung Cancer

Lung cancer is among the most common cancers with a high mortality rate worldwide. Despite the significant advances in diagnostic and therapeutic approaches, lung cancer prognoses and survival rates remain poor due to late diagnosis, drug resistance, and adverse effects. Therefore, new intervention therapies, such as the use of natural compounds with decreased toxicities, have been considered in lung cancer therapy. Curcumin, a natural occurring polyphenol derived from turmeric (Curcuma longa) has been studied extensively in recent years for its therapeutic effects. It has been shown that curcumin demonstrates anti-cancer effects in lung cancer through various mechanisms, including inhibition of cell proliferation, invasion, and metastasis, induction of apoptosis, epigenetic alterations, and regulation of microRNA expression. Several in vitro and in vivo studies have shown that these mechanisms are modulated by multiple molecular targets such as STAT3, EGFR, FOXO3a, TGF-β, eIF2α, COX-2, Bcl-2, PI3KAkt/mTOR, ROS, Fas/FasL, Cdc42, E-cadherin, MMPs, and adiponectin. In addition, limitations, strategies to overcome curcumin bioavailability, and potential side effects as well as clinical trials were also reviewed.

Comparative Studies on the Antioxidant Profiles of Curcumin and Bisdemethoxycurcumin in Erythrocytes and Broiler Chickens

Simple Summary

Turmeric, which is the rhizome of Curcuma longa, has a long history for spice and medicine in China, India, and other tropical countries. Curcuminoids, as the principle active compounds of turmeric, consist of curcumin (about 77%), demethoxycurcumin (about 17%), and bisdemethoxycurcumin (about 3%). Studies showed that curcuminoids, especially curcumin, possesses antioxidant, free radical scavenging activities, and thus have a health-promoting effect in human and animals. Of the three curcuminoids, extensive research on the biological activity of curcumin was carried out for decades. However, its natural analogues bisdemethoxycurcumin was relatively less investigated. Based the records, there was still controversy regarding the relative potency of antioxidant activity of curcuminoid that is dependent on different cell types and animal models, which ultimately affected their beneficial effects on the intestinal health and animal production as well. Thus, whether curcumin and bisdemethoxycurcumin shared the same efficiency of antioxidant activity in chicken erythrocytes and broiler chickens remains unknown. Our results demonstrated, for the first time, that the bisdemethoxycurcumin, acting like curcumin, exerted good free radical scavenging activity in erythrocytes and improved the redox status in broilers, although there were some slight differences in their efficiency of antioxidant activities in broiler chickens.

Abstract

The aim of this study was to investigate the antioxidant effects of curcumin and bisdemethoxycurcumin in both 2,20-azobis(2-amidinopropane) dihydrochloride (AAPH)-treated erythrocytes and broiler chickens. In experiment 1, chicken erythrocytes were employed to determine the antioxidant protection against AAPH treatment. Significant differences in hemolysis, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content were observed between the control and curcuminoids-treated groups. In experiment 2, a total of 480 Arbor Acres broilers with the similar body weights were used. All of the birds were fed basal diet and basal diet with 150 mg/kg curcumin or bisdemethoxycurcumin, respectively. The results showed that curcuminoids significantly increased ADG, serum antioxidant capacity, the glutathione redox potential of small intestine, the gene expression of Nrf2, and its related antioxidant enzymes. Besides, curcumin and bisdemethoxycurcumin increased the antioxidant activities of serum, diet, and excreta while using the 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt and ferric-reducing antioxidant power methods. It was concluded that bisdemethoxycurcumin, acting like curcumin, exerted good free radical scavenging activity in erythrocytes and improved the redox status in broilers, although there were some slight differences in their efficiency of antioxidant activities.

Curcumin Analogues with Aldose Reductase Inhibitory Activity: Synthesis, Biological Evaluation, and Molecular Docking

Curcumin, a constituent of Curcuma longa, has shown numerous biological and pharmacological activities, including antidiabetic effects. Here, a novel series of curcumin analogues were synthesized and evaluated for in vitro inhibition of aldose reductase (AR), the first and rate-limiting enzyme of the polyol pathway, which plays a key role in the onset and progression of diabetic complications. Biological activity studies showed that all the curcuminoids exhibited moderate to good AR inhibitory (ARI) activities compared with that of the quercetin standard. Importantly, compounds 8d, 8h, 9c, 9e, and 10g demonstrated promising ARI activities, with the 50% inhibitory concentration (IC50) values of 5.73, 5.95, 5.11, 5.78, and 5.10 µM, respectively. Four other compounds exhibited IC50 values in the range of 6.04–6.18 µM. Methyl and methoxy derivatives showed a remarkable ARI potential compared with that of other substitutions on the aromatic ring. Molecular docking experiments demonstrated that the most active curcuminoid (10g) was able to favorably bind in the active site of the AR enzyme. The potent ARI activities exhibited by the curcuminoids were attributed to their substitution patterns on the aromatic moiety, which may provide novel leads in the development of therapeutics for the treatment of diabetic complications.

The mechanism(s) of action of antioxidants: From scavenging reactive oxygen/nitrogen species to redox signaling and the generation of bioactive secondary metabolites

Small molecule, dietary antioxidants exert a remarkably broad range of bioactivities, and many of these can be explained by the influence of antioxidants on the redox homeostasis. Such compounds help to modulate the levels of harmful reactive oxygen/nitrogen species, and therefore participate in the regulation of various redox signaling pathways. However, upon ingestion, antioxidants usually undergo extensive metabolism that can generate a wide range of bioactive metabolites. This makes it difficult, but otherwise a need, to identify the ones responsible for the different activities of antioxidants. By better understanding their ways of action, the use of antioxidants in therapy can be improved. This review provides a summary on the role of the in vivo metabolic changes and the oxidized metabolites on the mechanisms behind the bioactivity of antioxidants. A special attention is given to metabolites described as products of biomimetic oxidative chemical reactions, which can be considered as models of free radical scavenging. During such reactions a wide variety of metabolites are formed, and they can exert completely different specific bioactivities as compared to their parent antioxidants. This implies that exploring the free radical scavenging-related metabolite fingerprint of each antioxidant molecule, collectively defined here as the scavengome, will lead to a deeper understanding of the bioactivity of these compounds. Furthermore, this paper aims to be a working tool for systematic studies on oxidized metabolic fingerprints of antioxidants, which will certainly reveal an often-neglected segment of chemical space that is a treasury of bioactive compounds.

Protonation of Curcumin Triggers Sequential Double Cyclization in the Gas-Phase: An Electrospray Mass Spectrometry and DFT Study

ESI-protonated natural curcumin (1) undergoes gas-phase cyclization and dissociates via competitive expulsions of 2-methoxy phenol and C₄H₄O₂ (diketene or an isomer). Evidence from mechanistic mass spectrometry and from Density Functional Theory (DFT) reveals that a two-step sequential cyclization occurs for the protonated molecule prior to the unusual loss of the elements of 2-methoxy phenol. Furthermore, the presence of the methoxy group at postion-3 is essential for the second cyclization. The transformation of curcumin upon protonation in the gas phase may be predictive of its solution chemistry and explain how curcumin plays a protective role in biology.

The impact of curcumin and its modified formulations on Alzheimer's disease

Alzheimer's disease (AD) is a major health problem worldwide, with no effective treatment approach. Curcumin is the main ingredient of turmeric traditionally used in Asian medicine. Several experimental studies have indicated the protective effect of curcumin and its novel formulations in AD. Curcumin has antioxidant, anti-inflammatory and neurotrophic activities, proposing a strong potential to prevent neurodegenerative diseases. However, there are no sufficient clinical trials to confirm curcumin use in AD patients. Low bioavailability following oral administration of curcumin limits its usage in human. The present study was designed to gather the effects of curcumin and its modified formulations in human and experimental models of AD.

A Review of Curcumin and Its Derivatives as Anticancer Agents

Cancer is the second leading cause of death in the world and one of the major public health problems. Despite the great advances in cancer therapy, the incidence and mortality rates of cancer remain high. Therefore, the quest for more efficient and less toxic cancer treatment strategies is still at the forefront of current research. Curcumin, the active ingredient of the Curcuma longa plant, has received great attention over the past two decades as an antioxidant, anti-inflammatory, and anticancer agent. In this review, a summary of the medicinal chemistry and pharmacology of curcumin and its derivatives in regard to anticancer activity, their main mechanisms of action, and cellular targets has been provided based on the literature data from the experimental and clinical evaluation of curcumin in cancer cell lines, animal models, and human subjects. In addition, the recent advances in the drug delivery systems for curcumin delivery to cancer cells have been highlighted.

Synthesis of Non-Symmetrical Nitrogen-Containing Curcuminoids in the Pursuit of New Anticancer Candidates

Curcumin is known to display pronounced anticancer effects and a variety of other biological activities. However, the low bioavailability and fast metabolism of this molecule present an issue of concern with respect to its medicinal applications. To address this issue, structural modifications of the curcumin scaffold can be envisioned as a strategy to improve both the solubility and stability of this chemical entity, without compromising its biological activities. Previous work in our group targeted the synthesis of symmetrical azaheteroaromatic curcuminoids, which showed better solubility and cytotoxicity profiles compared to curcumin. In continuation of that work, we now focused on the synthesis of non-symmetrical nitrogen-containing curcuminoids bearing both a phenolic and an azaheteroaromatic moiety. In that way, we aimed to combine good solubility, antioxidant potential and cytotoxic properties into one molecule. Some derivatives were selected for further chemical modification of their rather labile β-diketone scaffold to the corresponding pyrazole moiety. In this way, thirteen new non-symmetrical aza-aromatic curcuminoids and four pyrazole-based analogues were successfully synthesized in a yield of 11-69 %. All newly synthesized analogues were evaluated for their antioxidant properties, reactive oxygen species (ROS) production, water solubility and anticancer activities. Several novel derivatives displayed good cytotoxicity profiles compared to curcumin, in combination with an improved water solubility and stability, and were thus identified as potential hit scaffolds for further optimization studies.

Bioactivity of dietary polyphenols: The role of metabolites

A polyphenol-rich diet protects against chronic pathologies by modulating numerous physiological processes, such as cellular redox potential, enzymatic activity, cell proliferation and signaling transduction pathways. However, polyphenols have a low oral bioavailability mainly due to an extensive biotransformation mediated by phase I and phase II reactions in enterocytes and liver but also by gut microbiota. Despite low oral bioavailability, most polyphenols proved significant biological effects which brought into attention the low bioavailability/high bioactivity paradox. In recent years, polyphenol metabolites have attracted great interest as many of them showed similar or higher intrinsic biological effects in comparison to the parent compounds. There is a huge body of literature reporting on the biological functions of polyphenol metabolites generated by phase I and phase II metabolic reactions and gut microbiota-mediated biotransformation. In this respect, the review highlights the pharmacokinetic fate of the major dietary polyphenols (resveratrol, curcumin, quercetin, rutin, genistein, daidzein, ellagitannins, proanthocyanidins) in order to further address the efficacy of biometabolites as compared to parent molecules. The present work strongly supports the contribution of metabolites to the health benefits of polyphenols, thus offering a better perspective in understanding the role played by dietary polyphenols in human health.

Antioxidant activity of different species and varieties of turmeric (Curcuma spp): Isolation of active compounds

There are >80 species of turmeric (Curcuma spp.) and some species have multiple varieties, for example, Curcuma longa (C. longa) has 70 varieties. They could be different in their chemical properties and biological activities. Therefore, we compared antioxidant activity, total phenolic and flavonoid content of different species and varieties of turmeric namely C. longa [variety: Ryudai gold (RD) and Okinawa ukon], C. xanthorrhiza, C. aromatica, C. amada, and C. zedoaria. The antioxidant activity was determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, oxygen radical absorbance capacity (ORAC), reducing power and 2-deoxyribose (2-DR) oxidation assay. Our results suggested that RD contained significantly higher concentrations of total phenolic (157.4 mg gallic acid equivalent/g extract) and flavonoids (1089.5 mg rutin equivalent/g extract). RD also showed significantly higher DPPH radical-scavenging activity (IC₅₀: 26.4 μg/mL), ORAC (14,090 μmol Trolox equivalent/g extract), reducing power absorbance (0.33) and hydroxyl radical scavenging activity (IC₅₀: 7.4 μg/mL). Therefore, RD was chosen for the isolation of antioxidant compounds using silica gel column, Toyopearl HW-40F column, and high-performance liquid chromatography. Structural identification of the compounds was conducted using ¹H NMR, ¹³C NMR, and liquid chromatography-tandem mass spectrometry. The purified antioxidant compounds were bisabolone-9-one (1), 4-methyllene-5-hydroxybisabola-2,10-diene-9-one (2), turmeronol B (3), 5-hydroxy-1,7-bis(4-hydroxy-3-methoxyphenyl)-1-hepten-3-one (4), 3-hydroxy-1,7-bis(4-hydroxyphenyl)-6-hepten-1,5-dione (5), cyclobisdemethoxycurcumin (6), bisdemethoxycurcumin (7), demethoxycurcumin (8) and curcumin (9). The IC₅₀ for DPPH radical-scavenging activity were 474, 621, 234, 29, 39, 257, 198, 47 and 18 μM and hydroxyl radical-scavenging activity were 25.1, 24.4, 20.2, 2.1, 5.1, 17.2, 7.2, 3.3 and 1.5 μM for compound 1, 2, 3, 4, 5, 6, 7, 8 and 9, respectively. Our findings suggested that the RD variety of C. longa, developed by the University of the Ryukyus, Okinawa, Japan, is a promising source of natural antioxidants.

miR-15b-5p targeting amyloid precursor protein is involved in the anti-amyloid eflect of curcumin in swAPP695-HEK293 cells

Curcumin exerts a neuroprotective effect on Alzheimer's disease; however, it is not known whether microRNAs are involved in this protective effect. This study was conducted using swAPP695-HEK293 cells as an Alzheimer's disease cell model. swAPP695-HEK293 cells were treated with 0, 0.5, 1, 2, 5, and 10 μM curcumin for 24 hours. The changes in miR-15b-5p, miR-19a-3p, miR-195-5p, miR-101-3p, miR-216b-5p, miR-16-5p and miR-185-5p expression were assessed by real-time quantitative polymerase chain reaction. The mRNA and protein levels of amyloid precursor protein, amyloid-β40 and amyloid-β42 were evaluated by quantitative real-time polymerase chain reaction, western blot assays and enzyme-linked immunosorbent assays. swAPP695-HEK293 cells were transfected with miR-15b-5p mimic, or treated with 1 μM curcumin 24 hours before miR-15b-5p inhibitor transfection. The effects of curcumin on amyloid precursor protein, amyloid-β40 and amyloid-β42 levels were evaluated by western blot assays and enzyme-linked immunosorbent assay. Luciferase assays were used to analyze the interaction between miR-15b-5p and the 3'-untranslated region of amyloid precursor protein. The results show that amyloid precursor protein and amyloid-β expression were enhanced in swAPP695-HEK293 cells compared with HEK293 parental cells. Curcumin suppressed the expression of amyloid precursor protein and amyloid-β and up-regulated the expression of miR-15b-5p in swAPP695-HEK293 cells. In addition, we found a negative association of miR-15b-5p expression with amyloid precursor protein and amyloid-β levels in the curcumin-treated cells. Luciferase assays revealed that miR-15b-5p impaired the luciferase activity of the plasmid harboring the 3'-untranslated region of amyloid precursor protein. These findings indicate that curcumin down-regulates the expression of amyloid precursor protein and amyloid-β in swAPP695-HEK293 cells, which was partially mediated by miR-15b-5p via targeting of the 3'-untranslated region of amyloid precursor protein.

Green synthesis and biological activity of silver-curcumin nanoconjugates

AIM

There is an urgent need to develop alternative antimicrobial agents and, one of which is via the use of nanotechnology. Green synthetic routes are recently being replaced for nanoparticles preparation. Methods results: Silver-curcumin nanoconjugates (Ag-CurNCs) were prepared in an eco-friendly method. The prepared nanomaterials were characterized and the photostability was studied under the influence of UV irradiation. Results showed that, the conjugation between curcumin and silver in the nanoform improve the photostability of curcumin. Cytotoxicity was studied on different skin cell lines, and antibacterial activity was investigated against Escherichia coli. Results revealed the antibacterial activity of the prepared nanoconjugates (Ag-CurNCs) with minimal toxicity to skin cells.

CONCLUSION

Silver nanoparticles improve the photostability and antibacterial activity of curcumin, while curcumin helps in preparing biocompatible silver nanoparticles.

Nanoformulation of curcumin-loaded eudragit-nutriosomes to counteract malaria infection by a dual strategy: Improving antioxidant intestinal activity and systemic efficacy

In this paper, nutriosomes (phospholipid vesicles associated with Nutriose® FM06) were modified to obtain new systems aimed at enhancing the efficacy of curcumin in counteracting malaria infection upon oral administration. Eudragit® L100, a pH-sensitive co-polymer, was added to these vesicles, thus obtaining eudragit-nutriosomes, to improve their in vivo performances. Liposomes without eudragit and nutriose were also prepared as a reference. Cryo-TEM images showed the formation of multicompartment vesicles, with mean diameter around 300 nm and highly negative zeta potential. Vesicles were stable in fluids mimicking the gastro-intestinal content due to the high phospholipid concentration and the presence of gastro-resistant eudragit and digestion-resistant nutriose. Eudragit-nutriosomes disclosed promising performances in vitro and in vivo: they maximized the ability of curcumin to counteract oxidative stress in intestinal cells (Caco-2), which presumably reinforced its systemic efficacy. Orally-administered curcumin-loaded eudragit-nutriosomes increased significantly the survival of malaria-infected mice relative to free curcumin-treated controls.

Tetrahydrocurcumin and octahydrocurcumin, the primary and final hydrogenated metabolites of curcumin, possess superior hepatic-protective effect against acetaminophen-induced liver injury: Role of CYP2E1 and Keap1-Nrf2 pathway

Acetaminophen (APAP) overdose-induced hepatotoxicity is tightly associated with oxidative stress. Tetrahydrocurcumin (THC) and octahydrocurcumin (OHC), the primary and final hydrogenated metabolites of curcumin (CUR), possess stronger antioxidant activity in vitro. The present study was performed to investigate the potential and mechanism of OHC and THC against APAP-induced hepatotoxicity in parallel to CUR. Our results showed that OHC and THC dose-dependently enhanced liver function (ALT and AST levels) and alleviated histopathological deterioration. Besides, OHC and THC significantly restored the hepatic antioxidant status by miring level of MDA and ROS, and elevated levels of GSH, SOD, CAT and T-AOC. In addition, OHC and THC markedly suppressed the activity and expressions of CYP2E1, and bound to the active sites of CYP2E1. Moreover, OHC and THC activated the Keap1-Nrf2 pathway and enormously enhanced the translational activation of Nrf2-targeted gene (GCLC, GCLM, NQO1 and HO-1) against oxidative stress, via inhibiting the expression of Keap1 and blocking the interaction between Keap1 and Nrf2. Particularly, OHC and THC exerted superior hepato-protective and antioxidant activities to CUR. In conclusion, OHC and THC possess favorable hepato-protective effect through restoring antioxidant status, inhibiting CYP2E1 and activating Keap1-Nrf2 pathway, which might represent promising antioxidants for the treatment of APAP-induced hepatotoxicity.

The environmental pollutant, polychlorinated biphenyls, and cardiovascular disease: a potential target for antioxidant nanotherapeutics

Despite production having stopped in the 1970s, polychlorinated biphenyls (PCBs) represent persistent organic pollutants that continue to pose a serious human health risk. Exposure to PCBs has been linked to chronic inflammatory diseases, such as cardiovascular disease, type 2 diabetes, obesity, as well as hepatic disorders, endocrine dysfunction, neurological deficits, and many others. This is further complicated by the PCB's strong hydrophobicity, resulting in their ability to accumulate up the food chain and to be stored in fat deposits. This means that completely avoiding exposure is not possible, thus requiring the need to develop intervention strategies that can mitigate disease risks associated with exposure to PCBs. Currently, there is excitement in the use of nutritional compounds as a way of inhibiting the inflammation associated with PCBs, yet the suboptimal delivery and pharmacology of these compounds may not be sufficient in more acute exposures. In this review, we discuss the current state of knowledge of PCB toxicity and some of the antioxidant and anti-inflammatory nanocarrier systems that may be useful as an enhanced treatment modality for reducing PCB toxicity.

A novel bioavailable hydrogenated curcuminoids formulation (CuroWhite™) improves symptoms and diagnostic indicators in rheumatoid arthritis patients - A randomized, double blind and placebo controlled study

Rheumatoid arthritis (RA) is an inflammatory disease that cause chronic pain, disability and joint destruction. The present placebo controlled randomized study aimed to evaluate the efficacy of a novel hydrogenated curcuminoid formulation-CuroWhite™, in rheumatoid arthritis (RA) patients. Twenty four RA patients were randomized in 1:1:1 ratio to receive 250 mg, 500 mg CuroWhite or placebo as one capsule a day, over a period of three months. Improvement in the ACR response, changes in disease activity assessed using the DAS 28 score, change in physical function assessed on change in ESR, CRP, RF values were evaluated before and after the study. Results suggested that patients who received CuroWhite both low and high doses reported statistically significant changes in their clinical symptoms towards end of the study when compared with placebo. There were significant changes in DAS28 (50–64%) VAS (63–72%) ESR (88–89%), CRP (31–45%) RF (80–84%) values and ACR response for CuroWhite groups in comparison with placebo. Thus, CuroWhite acts as the analgesic and anti-inflammatory product for management of RA by the reduction of the inflammatory action which was confirmed by improvement in ESR, CRP, VAS, RF, DAS-28 and ACR responses. CuroWhite was significantly effective against RA with highly safe without serious side effects and well tolerated.

Tetrahydrocurcumin, a major metabolite of curcumin, ameliorates allergic airway inflammation by attenuating Th2 response and suppressing the IL-4Rα-Jak1-STAT6 and Jagged1/Jagged2 -Notch1/Notch2 pathways in asthmatic mice

BACKGROUND

Curcumin (Cur), derived from Curcuma species, exhibits anti-inflammatory, antioxidant, and anticancer effects. Although Cur has some beneficial effects on asthma, its clinical application is limited by its low bioavailability. Tetrahydrocurcumin (THC), the major active metabolite of Cur, has multiple biological functions, similarly to Cur, and importantly, it showed enhanced bioavailability in tissues and plasma. However, the effect of THC on asthma has not been reported.

OBJECTIVE

The current study sought to investigate the efficacy of dietary THC on allergic asthma compared to that of Cur in an animal model.

METHODS

The anti-inflammatory effects of Cur and THC were evaluated in an ovalbumin-induced asthmatic mouse model. The nasal symptoms, pathological alterations of the lung tissues, oxidants and antioxidants, cytokine production, T cell subsets, and Th2-related signalling pathway activity were assessed.

RESULTS

Both THC and Cur had beneficial effects on asthmatic mice with regard to nasal symptoms, pathological changes (eosinophils and mucus hyper-production), oxidative stress (malondialdehyde), cytokine production (IL-13), Th17 and cytotoxic T cell subsets, and Th2 signalling pathway (IL-4Rα-Jak1-STAT6 and Jagged1/Jagged2-Notch1/Notch2 axis) activity. THC was more effective than Cur in suppressing tissue eosinophilia, mucus production, and IL-4Rα/Jak1/STAT6 pathway activity. Furthermore, only THC inhibited peripheral eosinophil levels, Th2 cytokines (IL-4 and IL-5), and Th2 cell subsets and enhanced an antioxidant enzyme (glutathione).

CONCLUSION AND CLINICAL RELEVANCE

The above results demonstrated for the first time that THC was superior to Cur in modulating allergic asthmatic phenotypes, especially attenuating the Th2 response. THC might be a potentially effective agent for asthma treatment.

Curcumin-mediated effects on anti-diabetic drug-induced cardiotoxicity

The present study was designed to compare the cardiotoxicity of two very commonly used anti-diabetic drugs namely pioglitazone (Pio) and metformin (Met); and to study the effects of curcumin (Curc) against these drug-induced cardiotoxicity. Curc, being an anti-oxidant molecule and having cardio-protective potential, can have promising synergistic effects in reducing the cardiac stress induced by anti-diabetic therapies. Various dose and time-dependent cell viability and oxidative stress assays were conducted to study cardiotoxic side-effects and Curc-mediated effects in cardiomyoblasts. Effects of Curc were also studied in hyperglycaemia induced cardiac stress in the presence of drugs. Quantitative assays for cell growth, reactive oxygen species (ROS) generation, lipid peroxidation and mitochondrial permeability followed by anti-oxidant enzymes and caspases activity assays were done to study the mechanism of action of the induced cardiotoxicity. Significant dose and time mediated deleterious effects of Pio and Met were witnessed. Oxidative stress studies showed a remarkable increase in ROS with increasing dose of anti-diabetic drugs. Increased caspase activity and altered mitochondrial integrity were also witnessed in presence of Met and Pio in cardiomyoblasts. These alterations were found to be significantly reduced when treated with Curc simultaneously. The study confirms that Met and Pio exert toxic effects on cardiac cells by generating oxidative stress. Curc, being an anti-oxidative molecule, can suppress this effect and, therefore, can be used as a supplement with anti-diabetic drugs to suppress the induced cardiac stress.

Dietary curcumin supplementation attenuates inflammation, hepatic injury and oxidative damage in a rat model of intra-uterine growth retardation

Rats with a normal birth weight (NBW) or intra-uterine growth retardation (IUGR) were fed basic diets (NBW and IUGR groups) or basic diets supplemented with curcumin (NC and IC groups) from 6 to 12 weeks. The body weight of IUGR rats was lower (P<0·05) than that of the controls. Rats with IUGR showed higher (P<0·05) concentrations of TNF-α, IL-1β and IL-6; higher (P<0·05) activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in their serum; and increased (P<0·05) concentrations of malondialdehyde (MDA), protein carbonyl (PC) and 8-hydroxy-2'-deoxyguanosine (8-OHDG) in the liver compared with the NBW rats. The livers of IUGR rats exhibited a lower (P<0·05) superoxide dismutase activity and decreased (P<0·05) metabolic efficiency of the hepatic glutathione redox cycle compared with those of the NBW rats. In response to dietary curcumin supplementation, concentrations of inflammatory cytokines and activities of AST and ALT in the serum and MDA, PC and 8-OHDG in the liver were lower (P<0·05), and the hepatic glutathione redox cycle in the liver was improved (P<0·05) in the IC group than in the IUGR group. These results were associated with lower (P<0·05) phosphorylated levels of the NF-κB pathway and Janus kinase 2 (JAK2) and higher (P<0·05) mRNA expression of genes involved in the nuclear factor, erythroid 2-like 2 (Nfe2l2)/antioxidant response element (ARE) pathway in the liver of the IC rats than that of the IUGR rats. Maternal undernutrition decreased birth weight and led to inflammation, oxidative damage and injury in rats. Curcumin appeared to be beneficial in preventing IUGR-induced inflammation, oxidative damage and injury by activating the expression of the NF-κB, JAK/STAT and Nfe2l2/ARE pathways in the liver.

Biological and pharmacological effects of hexahydrocurcumin, a metabolite of curcumin

Curcumin, one of the most precious pharmacologically relevant natural products, has gained considerable attention among scientists for decades because of its multi-pharmacological activities in the clinical. However, critical studies on its pharmacological and toxicological activities are needed to understand how this compound can have these biological functions considering its poor oral bioavailability and the low plasma concentration. Moreover, curcumin undergoes extensive and rapid metabolism in vivo, indicating that the pharmacological activity of consuming curcumin might be mediated partly by its metabolites. And as one of the major curcumin metabolites, hexahydrocurcumin (HHC), exhibits similar or more potent bioactivity than curcumin by in vitro and in vivo studies, such as antioxidant, anti-inflammatory, antitumor and cardiovascular protective properties, which may provide important information for us to have a profound comprehension of the effectiveness of curcumin. This review mainly summarizes the current knowledge and underlying molecular mechanisms of the biological activities of HHC and its potential effects on the development of various human diseases.