The dark side of curcumin.
TL;DR: The purpose of this letter is to briefly review the negative properties of curcumin so that they can be balanced against its beneficial effects and suggests that the therapeutic potential of oralCurcumin is limited.
Abstract: Dear Editor, Curcumin is a yellow–orange pigment obtained from the plant Curcuma longa. The powdered rhizome of this plant, called turmeric, is a common ingredient in curry powders and has a long history of use in traditional Asian medicine for a wide variety of disorders. In the last decade a large number of reports have been published on the beneficial effects of curcumin, and it has repeatedly been claimed that this natural product is efficient and safe for the prevention and treatment of several diseases including cancer. It is not surprising, therefore, that curcumin is currently sold as a dietary supplement and that numerous clinical trials are ongoing or recruiting participants to evaluate curcumin activity. But there is accumulating evidence that curcumin may not be so effective and safe. Because such evidence is not generally acknowledged, the purpose of this letter is to briefly review the negative properties of curcumin so that they can be balanced against its beneficial effects. Most of the evidence that supports the therapeutic potential of curcumin is mainly based on in vitro studies in which curcumin was tested at concentrations in the micromolar range. Several reports have demonstrated, however, that the plasma concentrations of curcumin in people taking relatively high oral doses of this compound are very low, typically in the nanomolar range (reviewed in Ref. 4). For instance, a recent study examined the pharmacokinetics of a curcumin preparation in 12 healthy human volunteers 0.25–72 hr after an oral dose of 10 or 12 g. Using a high-performance liquid chromatography assay with a limit of detection of 50 ng mL , only 1 subject had detectable free curcumin at any of the time points assayed. The fact that curcumin also undergoes extensive metabolism in intestine and liver means that high concentrations of curcumin cannot be achieved and maintained in plasma and tissues after oral ingestion. This is a major obstacle for the clinical development of this agent and suggests that the therapeutic potential of oral curcumin is limited. The low clinical efficiency of curcumin in the treatment of several chronic diseases such as Alzheimer’s disease and cardiovascular diseases has been discussed recently. As far as cancer is concerned, in vitro studies have demonstrated that cancer cells do not die unless they are exposed to curcumin concentrations of 5–50 lM for several hours. Because of its poor bioavailability, these concentrations are not achieved outside the gastrointestinal tract when curcumin is taken orally. Because of its extensive metabolism in intestine and liver, these concentrations cannot be maintained for several hours in the gastrointestinal tract. This suggests that the chemotherapeutic potential of oral curcumin is limited even for the treatment of cancers of the gastrointestinal tract. Accordingly, when 15 patients with advanced colorectal cancer were treated with curcumin at daily doses of 3.6 g for up to 4 months, no partial responses to treatment or decreases in tumor markers were observed. A search of the website www.clinicaltrials.gov in July 2009 showed 34 clinical trials using curcumin in a wide variety of diseases, particularly in cancer. In some of these trials, patients with several types of cancer are receiving or will receive curcumin through the oral route. For instance, in an ongoing Phase II clinical trial (NCT00094445), participants with pancreatic cancer are receiving 8 g of curcumin by mouth every day for several 8-week-periods. As discussed before, the plasma concentrations of curcumin in people taking relatively high oral doses of curcumin are very low, typically in the nanomolar range. This means that the oral administration of curcumin does not lead to cytotoxic concentrations outside the gastrointestinal tract. If one assumes that tumor cell death is necessary to achieve an efficient therapeutic response, one should not expect a very positive outcome from this trial. A Phase II Trial is also recruiting participants to test if a daily oral dose of 8 g of curcumin can improve the efficacy of the standard chemotherapy gemcitabine in patients with locally advanced or metastatic adenocarcinoma of the pancreas (NCT00192842). The rationale for this trial is based on in vitro and in vivo data that suggest that noncytotoxic concentrations of curcumin may sensitize cancer cells to the effects of anticancer drugs such as gemcitabine. Although a daily dose of 1 g kg 1 of curcumin increased the antitumor effects of gemcitabine in an orthotopic model of pancreatic cancer, this dose of curcumin (e.g. 70 g in a 70-kg person) is almost 10 times higher than that used in the clinical trial testing the combination of curcumin and gemcitabine (8 g). This makes the outcome of this trial uncertain, as curcumin can either increase or reduce the efficiency of chemotherapy depending on the concentration at which it is used. Several strategies have been proposed to overcome the low oral bioavailability of curcumin. One of these strategies has entered clinical trials and consists of using the black pepper alkaloid piperine (bioperine) to increase the bioavailability of curcumin. This strategy, however, should be used cautiously, as piperine is a potent inhibitor of drug Le tt er s to th e E di to r
Citations
More filters
TL;DR: Evidence is provided that curcumin is an unstable, reactive, nonbioavailable compound and, therefore, a highly improbable lead and, on the basis of this in-depth evaluation, potential new directions for research onCurcuminoids are discussed.
Abstract: Curcumin is a constituent (up to ∼5%) of the traditional medicine known as turmeric. Interest in the therapeutic use of turmeric and the relative ease of isolation of curcuminoids has led to their extensive investigation. Curcumin has recently been classified as both a PAINS (pan-assay interference compounds) and an IMPS (invalid metabolic panaceas) candidate. The likely false activity of curcumin in vitro and in vivo has resulted in >120 clinical trials of curcuminoids against several diseases. No double-blinded, placebo controlled clinical trial of curcumin has been successful. This manuscript reviews the essential medicinal chemistry of curcumin and provides evidence that curcumin is an unstable, reactive, nonbioavailable compound and, therefore, a highly improbable lead. On the basis of this in-depth evaluation, potential new directions for research on curcuminoids are discussed.
1,191 citations
TL;DR: The role that polyphenols play in the prevention of cancer, cardiovascular disease and neurodegeneration is provided and epidemiological data, human intervention study findings, as well as animal and in vitro studies in support of these actions are presented.
Abstract: Polyphenols are found ubiquitously in plants and their regular consumption has been associated with a reduced risk of a number of chronic diseases, including cancer, cardiovascular disease (CVD) and neurodegenerative disorders. Rather than exerting direct antioxidant effects, the mechanisms by which polyphenols express these beneficial properties appear to involve their interaction with cellular signaling pathways and related machinery that mediate cell function under both normal and pathological conditions. We illustrate that their interactions with two such pathways, the MAP kinase (ERK, JNK, p38) and PI3 kinase/Akt signaling cascades, allow them to impact upon normal and abnormal cell function, thus influencing the cellular processes involved in the initiation and progression of cancer, CVD and neurodegeneration. For example, their ability to activate ERK in neurons leads to a promotion of neuronal survival and cognitive enhancements, both of which influence the progression of Alzheimer's disease, whilst ERK activation by polyphenols in vascular endothelial cells influences nitric oxide production, blood pressure and ultimately CVD risk. The main focus of this review is to provide an overview of the role that polyphenols play in the prevention of cancer, cardiovascular disease and neurodegeneration. We present epidemiological data, human intervention study findings, as well as animal and in vitro studies in support of these actions and in each case we consider how their actions at the cellular level may underpin their physiological effects.
641 citations
TL;DR: The recent findings concerning the effects of polyphenols on human health are summarized, the current limitations at pitfalls are analyzed, and future directions for research are proposed.
Abstract: The lay press often heralds polyphenols as panacea for all sorts of diseases. The rationale is that their antioxidant activity would prevent free radical damage to macromolecules. However, basic and clinical science is showing that the reality is much more complex than this and that several issues, notably content in foodstuff, bioavailability, or in vivo antioxidant activity are yet to be resolved. We summarize the recent findings concerning the effects of polyphenols on human health, analyze the current limitations at pitfalls, and propose future directions for research.
308 citations
Cites background from "The dark side of curcumin."
...Others studies have found an antiapoptotic effect mediated by a down-regulation of p53 expression and inhibition of the antiproliferative activity of chemotherapeutic agents on breast cancer growth (Burgos-Moron et al., 2009; Goel et al., 2008)....
[...]
TL;DR: The improved absorption, and possibly also a better plasma curcuminoid profile, might underlie the clinical efficacy of Meriva at doses significantly lower than unformulated cur cuminoid mixtures.
Abstract: The relative absorption of a standardized curcuminoid mixture and its corresponding lecithin formulation (Meriva) was investigated in a randomized, double-blind, crossover human study. Clinically validated dosages were used for both products, and plasma levels of all three major curcuminoids [curcumin (1a), demethoxycurcumin (1b), and bisdemethoxycurcumin (1c)] were evaluated. Total curcuminoid absorption was about 29-fold higher for Meriva than for its corresponding unformulated curcuminoid mixture, but only phase-2 metabolites could be detected, and plasma concentrations were still significantly lower than those required for the inhibition of most anti-inflammatory targets of curcumin. Remarkably, phospholipid formulation increased the absorption of demethoxylated curcuminoids much more than that of curcumin (1a), with significant differences in plasma curcuminoid profile between Meriva and its corresponding unformulated curcuminoid mixture. Thus, the major plasma curcuminoid after administration of Mer...
298 citations
Zabol University of Medical Sciences1, American University of Beirut2, Université Paris-Saclay3, University of Pisa4, Warsaw University of Life Sciences5, University of Alabama in Huntsville6, Shahid Beheshti University of Medical Sciences and Health Services7, University of Concepción8, Kendall College of Art and Design9, University of Melbourne10, Hospital Authority11, University of Fort Hare12, University of Porto13
TL;DR: This review aims to offer an in-depth discussion of curcumin applications for food and biotechnological industries, and on health promotion and disease prevention, with particular emphasis on its antioxidant, anti-inflammatory, neuroprotective, anticancer, hepatoprotective, and cardioprotective effects.
Abstract: Curcumin, a yellow polyphenolic pigment from the Curcuma longa L. (turmeric) rhizome, has been used for centuries for culinary and food coloring purposes, and as an ingredient for various medicinal preparations, widely used in Ayurveda and Chinese medicine. In recent decades, their biological activities have been extensively studied. Thus, this review aims to offer an in-depth discussion of curcumin applications for food and biotechnological industries, and on health promotion and disease prevention, with particular emphasis on its antioxidant, anti-inflammatory, neuroprotective, anticancer, hepatoprotective, and cardioprotective effects. Bioavailability, bioefficacy and safety features, side effects, and quality parameters of curcumin are also addressed. Finally, curcumin's multidimensional applications, food attractiveness optimization, agro-industrial procedures to offset its instability and low bioavailability, health concerns, and upcoming strategies for clinical application are also covered.
286 citations
References
More filters
TL;DR: Enhanced bioavailability of curcumin in the near future is likely to bring this promising natural product to the forefront of therapeutic agents for treatment of human disease.
Abstract: Curcumin, a polyphenolic compound derived from dietary spice turmeric, possesses diverse pharmacologic effects including anti-inflammatory, antioxidant, antiproliferative and antiangiogenic activities. Phase I clinical trials have shown that curcumin is safe even at high doses (12 g/day) in humans but exhibit poor bioavailability. Major reasons contributing to the low plasma and tissue levels of curcumin appear to be due to poor absorption, rapid metabolism, and rapid systemic elimination. To improve the bioavailability of curcumin, numerous approaches have been undertaken. These approaches involve, first, the use of adjuvant like piperine that interferes with glucuronidation; second, the use of liposomal curcumin; third, curcumin nanoparticles; fourth, the use of curcumin phospholipid complex; and fifth, the use of structural analogues of curcumin (e.g., EF-24). The latter has been reported to have a rapid absorption with a peak plasma half-life. Despite the lower bioavailability, therapeutic efficacy of...
4,275 citations
TL;DR: Prooxidant states can be caused by different classes of agents, including hyperbaric oxygen, radiation, xenobiotic metabolites and Fenton-type reagents, modulators of the cytochrome P-450 electron-transport chain, peroxisome proliferators, inhibitors of the antioxidant defense, and membrane-active agents.
Abstract: There is convincing evidence that cellular prooxidant states--that is, increased concentrations of active oxygen and organic peroxides and radicals--can promote initiated cells to neoplastic growth. Prooxidant states can be caused by different classes of agents, including hyperbaric oxygen, radiation, xenobiotic metabolites and Fenton-type reagents, modulators of the cytochrome P-450 electron-transport chain, peroxisome proliferators, inhibitors of the antioxidant defense, and membrane-active agents. Many of these agents are promoters or complete carcinogens. They cause chromosomal damage by indirect action, but the role of this damage in carcinogenesis remains unclear. Prooxidant states can be prevented or suppressed by the enzymes of the cellular antioxidant defense and low molecular weight scavenger molecules, and many antioxidants are antipromoters and anticarcinogens. Finally, prooxidant states may modulate the expression of a family of prooxidant genes, which are related to cell growth and differentiation, by inducing alterations in DNA structure or by epigenetic mechanisms, for example, by polyadenosine diphosphate-ribosylation of chromosomal proteins.
2,488 citations
Journal Article•
TL;DR: Constitutive generation of large amounts of reactive oxygen intermediates, if it occurs in vivo, might contribute to the ability of some tumors to mutate, inhibit antiproteases, injure local tissues, and therefore promote tumor heterogeneity, invasion, and metastasis.
Abstract: Few nonphagocytic cells are known to generate reactive oxygen intermediates. Based on horseradish peroxidase-dependent, catalase-inhibitable oxidation of fluorescent scopoletin, seven human tumor cell lines constitutively elaborated H2O2 at rates (up to 0.5 nmol/10(4) cells/h) large enough that cumulative amounts at 4 h were comparable to the amount of H2O2 produced by phorbol ester-triggered neutrophils. Superoxide dismutase-inhibitable ferricytochrome c reduction was detectable at much lower rates. H2O2 production was inhibited by diphenyleneiodonium, a flavoprotein binder (concentration producing 50% inhibition, 0.3 microM), and diethyldithiocarbamate, a divalent cation chelator (concentration producing 50% inhibition, 3 microM), but not by cyanide or azide, inhibitors of electron transport, or by agents that inhibit xanthine oxidase, polyamine oxidase, or cytochrome P450. Cytochrome b559, present in human phagocytes and lymphocytes, was undetectable in these tumor cells by a sensitive spectrophotometric method. Mouse fibroblasts transfected with human tyrosinase complementary DNA made melanin, but not H2O2. Constitutive generation of large amounts of reactive oxygen intermediates, if it occurs in vivo, might contribute to the ability of some tumors to mutate, inhibit antiproteases, injure local tissues, and therefore promote tumor heterogeneity, invasion, and metastasis.
2,417 citations
TL;DR: Curcumin, a spice once relegated to the kitchen shelf, has moved into the clinic and may prove to be "Curecumin", a therapeutic agent in wound healing, diabetes, Alzheimer disease, Parkinson disease, cardiovascular disease, pulmonary disease, and arthritis.
1,897 citations
TL;DR: The study shows that in the dosages used, piperine enhances the serum concentration, extent of absorption and bioavailability of curcumin in both rats and humans with no adverse effects.
Abstract: The medicinal properties of curcumin obtained from Curcuma longa L. cannot be utilised because of poor bioavailability due to its rapid metabolism in the liver and intestinal wall. In this study, the effect of combining piperine, a known inhibitor of hepatic and intestinal glucuronidation, was evaluated on the bioavailability of curcumin in rats and healthy human volunteers. When curcumin was given alone, in the dose 2 g/kg to rats, moderate serum concentrations were achieved over a period of 4 h. Concomitant administration of piperine 20 mg/kg increased the serum concentration of curcumin for a short period of 1-2 h post drug. Time to maximum was significantly increased (P < 0.02) while elimination half life and clearance significantly decreased (P < 0.02), and the bioavailability was increased by 154%. On the other hand in humans after a dose of 2 g curcumin alone, serum levels were either undetectable or very low. Concomitant administration of piperine 20 mg produced much higher concentrations from 0.25 to 1 h post drug (P < 0.01 at 0.25 and 0.5 h; P < 0.001 at 1 h), the increase in bioavailability was 2000%. The study shows that in the dosages used, piperine enhances the serum concentration, extent of absorption and bioavailability of curcumin in both rats and humans with no adverse effects.
1,599 citations
"The dark side of curcumin." refers methods in this paper
...One of these strategies has entered clinical trials and consists of using the black pepper alkaloid piperine (bioperine) to increase the bioavailability of curcumin.(14) This strategy, however, should be used cautiously, as piperine is a potent inhibitor of drug Le tt er s to th e E di to r...
[...]