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.

Monocarbonyl curcuminoids as antituberculosis agents with their moderate in-vitro metabolic stability on human liver microsomes.

Tuberculosis, an airborne infectious disease, results in a high morbidity and mortality rate. The continuous emergence of TB resistance strains including MDR (multidrug-resistant tuberculosis), XDR (extensive drug-resistant tuberculosis), and especially TDR (totally drug-resistant tuberculosis) is a major public health threat and has intensified the need to develop new antitubercular agents. A natural product, curcumin, possesses diverse biological activities but suffers due to a lack of water solubility and bioavailability. To overcome these limitations, a series of 17 water-soluble monocarbonyl curcuminoids was synthesized and evaluated for antimycobacterial activity. All compounds exhibited good to moderate anti-TB activity with MIC99 in the range of 3.12-25.0 µM, out of which 7c and 7p were found the most potent compounds with MIC99 in the range of 3.12-6.25 µM. Furthermore, these compounds were observed to be nonhaemolytic, nontoxic, and stable under both physiological as well as reducing conditions. In-vitro metabolic stability data of the representative compound 7p with the human liver microsome revealed that these compounds possess a moderate metabolism with a half-life of 1.2 h and an intrinsic clearance of 1.12 ml/h/mg.

Comparative bioavailability of curcuminoids from a water-dispersible high curcuminoid turmeric extract against a generic turmeric extract: a randomized, cross-over, comparative, pharmacokinetic study.

OBJECTIVES: The therapeutic utility of turmeric (Curcuma longa L., Zingiberaceae) is limited due to low bioavailability of its active principal curcuminoids. This study evaluates the pharmacokinetic characteristics of a natural, water-dispersible turmeric extract containing 60% curcuminoids (TurmXtra 60N), referred to as WDTE60N, compared to standard turmeric extract 95% (STE95). METHODS: This open-label, two-way crossover, single oral dose, comparative pharmacokinetic study, randomized 14 subjects to receive one capsule of WDTE60N (150 mg curcuminoids) or three capsules of STE95 (500 mg curcuminoids each). The resulting dose ratio of actives for WDTE60N:STE95 was 1:10. KEY FINDINGS: Peak plasma levels of free curcumin, total curcuminoids, tetrahydrocurcumin and demethoxycurcumin were similar (P > 0.05). Cmax of total curcumin was higher (P = 0.0253) for WDTE60N at a 10-fold lower dose compared to STE95 (43.5 ± 28.5 vs. 21.3 ± 10.7 ng/ml). Mean AUC0-t was higher (P < 0.001) for free curcumin and comparable for total curcumin and total curcuminoids with WDTE60N than with STE95. Five adverse events were reported in three subjects (mild in severity) and were unrelated to study products. CONCLUSION: WDTE60N showed higher absorption and comparable exposure for free curcumin, total curcumin and total curcuminoids at a 10-fold lower dose than STE95.

Nanomicellar curcuminoids attenuates renal ischemia/reperfusion injury in rat through prevention of apoptosis and downregulation of MAPKs pathways.

Renal ischemia/reperfusion (I/R) injury is considered as a main problem in clinical practice. Curcuminoids, the active constituents of turmeric, seem to have potential renoprotective effects. However, the poor bioavailability of curcuminoids restricts their therapeutic effects. In the present study, the effect of nanomicellar curcuminoids (NC) treatment on renal function, histology, total antioxidant capacity (TAC), total oxidative stress (TOS), caspase-3 level as well as mitogen activated protein kinases (MAPKs: JNK, p38 and ERK) phosphorylation were evaluated following renal I/R. Adult male Sprague-Dawley rats were administered NC at the dose of 25 mg/kg 1 h before renal ischemia induction. The animals were subjected to bilateral renal ischemia for 60 min and reperfusion for 24 h. Subsequently, blood urea nitrogen (BUN), creatinine (Cr), renal histopathology, TAC, TOS, and oxidative stress index, cleaved caspase-3 level, Bax and MAPKs signaling were evaluated. The results indicated that NC pretreatment at the dose of 25 mg/kg significantly improved renal function as well as histolopatholgical damages. Moreover, NC reduced the level of renal oxidative stress, cleaved caspase-3 and Bax (as the proapoptotic proteins) and suppressed the activated Jun N-terminal Kinase (JNK), p38 and extracellular receptor kinase (ERK) signaling induced by renal I/R. The findings of the current study indicate that NC might prevent the injury induced by renal I/R through suppression of oxidative stress, apoptosis and MAPKs pathways.

Demethoxycurcumin analogue DMC-BH exhibits potent anticancer effects on orthotopic glioblastomas.

Demethoxycurcumin (DMC) has anti-glioma effects in vitro and in subcutaneous xenotransplanted tumors. Our previous study confirmed that the molecule also has mild anti-glioma effects on orthotopic glioblastomas in vivo. In this study, we found that DMC-BH, a DMC analogue, exhibited more potent in vitro and in vivo activities than did DMC. DMC-BH was cytotoxic against various glioma cells including SHG-44, C6, U251, U87, A172 and primary glioma cells. DMC-BH activity was characterized by low acute toxicity and an appropriate pharmacokinetic profile. We evaluated the anti-tumor effects of DMC-BH in an ectopic xenograft model, an orthotopic glioblastoma xenograft model and a patient-derived tumor xenograft (PDTX) model. DMC-BH exhibited potent anti-tumor activity in both the ectopic xenograft and PDTX models. Indeed, bioluminescence measurements showed that DMC-BH exerted a significantly greater anti-tumor effect on orthotopic glioma growth than DMC. Immunohistochemical analysis revealed that DMC-BH inhibited expression of Ki67 and increased the incidence of TUNEL-positive cells. Western blotting showed that DMC-BH significantly decreased p-Akt and p-mTOR expression in orthotopic glioma tissues. These results suggest that the DMC analogue DMC-BH has potent anti-tumor properties that warrant further study.

Demethoxycurcumin analogue DMC-BH inhibits orthotopic growth of glioma stem cells by targeting JNK/ERK signaling.

Glioma stem cells (GSCs) play an important role in glioblastoma resistance to conventional therapies and disease recurrence. Here, we assessed the therapeutic effect of a demethoxycurcumin analogue, DMC-BH, on GSCs, and investigated the underlying mechanisms. Our in vitro data demonstrate that DMC-BH inhibits GSC proliferation, and induces apoptosis and autophagy in GSCs. In addition, our results show that DMC-BH effectively crosses the blood-brain barrier to inhibit the growth of intracranial GSC tumors in vivo. DMC-BH significantly increased phosphorylation levels of JNK, ERK and c-Jun in GSCs. Inhibition of JNK and ERK activities reversed the pro-apoptotic effect of DMC-BH in GSCs, indicating that the DMC-BH-induced apoptosis in GSCs is mediated via the JNK/ERK signaling pathway. These results suggest that DMC-BH could potentially serve as a effective therapy against GSCs that acts by targeting the JNK/ERK signaling pathway.

A novel predict-verify strategy for targeted metabolomics: Comparison of the curcuminoids between crude and fermented turmeric.

Curcuminoids are the major bioactive constituents of turmeric, the application of which are limited by the poor bioavailability. In this study, turmeric was fermented by the Monascus purpureus and Eurotium cristatum fungi to enhance its bioavailability. To explore the variations in the curcuminoids contents in fermented turmeric, a targeted predict-verify strategy was established. For targeted analysis of curcuminoids, a compound library containing all possible curcuminoids based on their structural skeleton was predicted and built for targeted scanning. Then, the MS data were automatically matched with the predicted library to verify the corresponding curcuminoids. As a result, 115 curcuminoids (48 novel compounds and 14 compounds reported in turmeric for the first time) were fully characterized in crude and fermented turmeric. Among these curcuminoids, 31 were newly generated in fermented turmeric. The established predict-verify strategy allows for an efficient and automatic metabolomic analysis to screen for curcuminoids with potentially better bioavailability.

Phospholipid/hydroxypropyl-ß-cyclodextrin supramolecular complexes are promising candidates for efficient oral delivery of curcuminoids.

Curcumin (Cur) and demethoxycurcumin (Dcur) are two natural analogues of phenol extracted from turmeric, possessing various pharmacological properties. However, their therapeutic potentials are substantially limited by their rather poor aqueous solubility and bioavailability. Herein, novel soluble supramolecular complexes of the two curcuminoids were firstly prepared by integrating phospholipid (PC) compound technology and a hydroxypropyl-ß-cyclodextrin (HPßCD) inclusion technique to enhance the bioavailability of the curcuminoids. The PC-HPßCD supramolecular complexes were demonstrated to show improved solubility, augmented drug release, enhanced in situ gastrointestinal absorption, and increased oral bioavailability. The significantly increased bioavailability might be attribute to the appropriate particle sizes (<200 nm), the near-neutral suface charges as well as the additional effects of PC and HPßCD. Overall, the PC-HPßCD supramolecular complexes may be considered as promising candidates for the efficient oral delivery of the curcuminoids; moreover, they are inexpensive, simple to prepare, and have good market prospects. Interestingly, the two natural analogues were found to be different in their in vivo bioavailability with or without supramolecular complexing, probably owing to the difference in the phenylmethoxy group. Therefore, Dcur may have a broader prospect in the pharmaceutical industry, based on its remarkable improvement in bioavailability and reported physiological activity.

Effect of different oleogelators on lipolysis and curcuminoid bioaccessibility upon in vitro digestion of sunflower oil oleogels.

Sunflower oil enriched with curcuminoid compounds (CUs) was gelled by adding 5% (w/w) saturated monoglycerides (MG), rice bran waxes (RW) or a mixture of ß-sitosterol and γ-oryzanol (PS). The resulting oleogels differed for rheological properties and firmness due to the difference in gel network structure. PS oleogel was the firmest sample followed by RW and MG ones. Upon in vitro digestion, fatty acid release as a function of digestion time was greatly affected by oleogel structure: the extent of lipolysis decreased as oleogel strength increased (PS < RW < MG). On the other hand, the nature of the oleogelator affected CUs bioaccessibility, which was lower in oleogels containing crystalline particles (MG and RW). These findings appear interesting in the attempt to develop oleogels able to control lipid digestion as well as to deliver bioactive molecules in food systems.

Pharmacokinetics and Tissue Distribution of Alnustone in Rats after Intravenous Administration by Liquid Chromatography-Mass Spectrometry.

Alnustone, a nonphenolic diarylheptanoid, first isolated from Alnus pendula (Betulaceae), has recently received a great deal of attention due to its various beneficial pharmacological effects. However, its pharmacokinetic profile in vivo remains unclear. The purpose of this study is to establish a fast and sensitive quantification method of alnustone using liquid chromatography tandem mass spectrometry (LC-MS/MS) and evaluate the pharmacokinetic and tissue distribution profiles of alnustone in rats. The sample was precipitated with acetonitrile with 0.5% formic acid and separated on BEH C18 Column. The mobile phase was composed of 0.1% formic acid in water and methanol at a flow rate of 0.3 mL/min. Alnustone and the internal standard (caffeine) were quantitatively monitored with precursor-to-product ion transitions of m/z 262.9→105.2 and m/z 195.2→138.0, respectively. The calibration curve for alnustone was linear from 1 to 2000 ng/mL. The intra- and inter-day assay precision (RSD) ranged from 1.1-9.0 % to 3.3-8.6%, respectively and the intra- and inter-day assay accuracy (RE) was between -8.2-9.7% and -10.3-9.9%, respectively. The validated method was successfully applied to the pharmacokinetic studies of alnustone in rats. After single-dose intravenous administration of alnustone (5 mg/kg), the mean peak plasma concentration (Cmax) value was 7066.36 ± 820.62 ng/mL, and the mean area under the concentration-time curve (AUC0-t) value was 6009.79 ± 567.30 ng/mL∙h. Our results demonstrated that the residence time of alnustone in vivo was not long and it eliminated quickly from the rat plasma. Meanwhile, the drug is mainly distributed in tissues with large blood flow, and the lung and liver might be the target organs for alnustone efficacy. The study will provide information for further application of alnustone.

Curcuminoids plus piperine improve nonalcoholic fatty liver disease: A clinical trial.

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) as a prevalent hepatic disease is associated with an increased risk of morbidity and mortality related to the liver and cardiovascular disease (CVD). Lifestyle modification and good metabolic control is the first line of treatment, but not always efficacious in reversing NAFLD pathogenesis. Curcumin is a dietary phytochemical with hepatoprotective activities, though its low bioavailability is considered as a major challenge for clinical applications. Therefore, in this study, in order to improve the bioavailability of curcumin, it was coadministered with piperine and we investigated the effects of this bioavailability-enhanced curcumin on serum hepatic enzymes, lipid profile, and glycemic indices in patients with NAFLD. METHODS: In this randomized controlled parallel-group trial, 70 subjects with ultrasound-determined NAFLD were randomized to either 500 mg curcuminoids coadministered with 5 mg piperine daily or placebo for 12 weeks. NAFLD severity (on the basis of sonography) and hepatic function was assessed at baseline and at the study end. RESULTS: Seventy subjects completed the study. Supplementation with curcuminoids plus piperine significantly reduced the hematocrit (P = 0.027), erythrocyte sedimentation rate (P = 0.048) and the serum concentrations of alanine aminotransferase (P = 0.035), aspartate aminotransferase (P = 0.042), alkaline phosphatase (P = 0.004), cholesterol (P < 0.016), low-density lipoprotein cholesterol (P < 0.017), Iron (P = 0.026), and Hemoglobin (P = 0.025) and increased total iron-binding capacity (P = 0.003). However, except albumin, changes in other parameters were not statistically different between groups. In addition, administration of curcuminoids plus piperine significantly improved NAFLD severity (P < 0.001), which was statistically different compared with the placebo group (P = 0.022). Also, the percentage of improved patients was marginally higher in the curcuminoids plus piperine group when compared with the placebo group (P = 0.058). CONCLUSION: This study suggested beneficial effects of combined curcuminoids and piperine supplementation on disease severity in patients with NAFLD.

Development and validation of an LC-MS/MS method for the determination of DPHB in rat plasma and its application in pharmacokinetic studies.

The aim of the present study was to develop a rapid, specific and sensitive LC-MS/MS method for the determination of DPHB [7-(4″-hydroxy-3″-methoxyphenyl)-1-phenyl-4-hepten-3-one] in rat plasma using yakuchinone A as an internal standard (IS). n-Hexane was used for the extraction of DPHB from rat plasma. Chromatographic separation of DPHB was achieved using a Kinetex XB-C18 column (2.10 × 50 mm, 2.6 µm) at 40°C. The mobile phase consisted of water (containing 0.1‰ formic acid, A) and acetonitrile (containing 0.1‰ formic acid, B) under a gradient elution at a flow rate of 0.3 mL min-1 . Positive electrospray ionization and multiple reaction monitoring mode were used for detection. The selected precursor ion to product ion pairs, m/z 311.3 → 137.0 for DPHB and m/z 313.1 → 137.0 for yakuchinone A, were monitored. Good linearity was observed over the concentration range from 2 to 2000 ng mL-1 (r = 0.9969). The recovery efficiency of DPHB from rat plasma was 54.8-69.7%, while the matrix effect ranged from 99.7 to 113%. Intra- and inter-day precision and accuracy values were within ±15% at three different quality control concentration levels. This validated method was successfully applied to pharmacokinetic studies in rats after a single p.o. or i.v. dose of DPHB solution. The route of administration significantly influenced systemic exposure to DPHB, and low bioavailability of DPHB was observed. The method developed here will be further improved and used in future pharmacokinetic studies.

Isoxazole-tethered diarylheptanoid analogs: Discovery of a new drug-like PAR2 antagonist.

A new class of isoxazole-tethered diarylheptanoids having characteristic 1,3-syn-diol and 1,3-anti-diol chemophoric moieties, e.g. 4a-d and 5a-c respectively, have been designed and synthesized starting from d-glucose following a stereo-conserved general synthetic strategy. The isoxazole heterocycle was installed using our recently elaborated methodology deploying Magtrieve™ as a selective oxidizing agent. Two of these new analogs 4a and 5a exhibited significantly improved in vitro drug-like properties including solubility, metabolic stability, cell permeability and lack of nonspecific cytotoxicity when compared with curcumin-I. In a HEK293 cell-based intracellular calcium [Ca2+]i release assay, 4a and 5a, when tested at 30 µM, inhibited the trypsin agonist induced protease-activated receptor-2 (PAR2) activity by 80% and 70% respectively. IC50 of 4a (SB70) has been determined as 6 µM which is in the same range of current benchmarks for PAR2 antagonists.

Increased in situ intestinal absorption of phytoestrogenic diarylheptanoids from Curcuma comosa in nanoemulsions.

Curcuma comosa has long been used as a gynecological medicine. Several diarylheptanoids have been purified from this plant, and their pharmacological effects were proven. However, there is no information about the absorption of C. comosa components to support the formulation usage. In the present study, C. comosa hexane extract and the mixture of its two major compounds, (4E,6E)-1,7-diphenylhepta-4,6-dien-3-ol (DA1) and (6E)-1,7-diphenylhept-6-en-3-ol (DA2), were formulated into nanoemulsions. The physical properties of the nanoemulsions and the in situ intestinal absorptions of DA1 and DA2 were evaluated. The results demonstrated the mean particle sizes at 0.207 ± 0.001 and 0.408 ± 0.014 µm, and the zeta potential at -14.57 ± 0.85 and -10.47 ± 0.32 mV for C. comosa nanoemulsion (C.c-Nano) and mixture of diarlylheptanoid nanoemulsions (DA-Nano), respectively. The entrapments of DA1 and DA2 were 76.61% and 75.41%, and 71.91% and 71.63% for C.c-Nano and DA-Nano, respectively. The drug loading ratios of DA1 and DA2 were 351.47 and 614.53 µg/mg, and 59.48 and 126.72 µg/mg for C.c-Nano and DA-Nano. The intestinal absorption rates of DA1 and DA2 were 0.329 ± 0.015 and 0.519 ± 0.026 µg/min/cm2 in C.c-Nano, and 0.380 ± 0.006 and 0.428 ± 0.036 µg/min/cm2 in DA-Nano, which were five to ten times faster than those in oil. In conclusion, the formulation in nanoemulsion forms obviously increased the intestinal absorption rate of diarylheptanoids.

Pharmacokinetics and organ distribution of diarylheptanoid phytoestrogens from Curcuma comosa in rats.

Curcuma comosa is widely used as a traditional herbal medicine for gynecological diseases in South East Asia. Previous studies reported that it has phytoestrogenic activity, and several diarylheptanoids were found to be the active constituents. In this study, the pharmacokinetics profile and organ distribution of three active compounds of C. comosa hexane extract were investigated. Rats were separately administered C. comosa hexane extract intravenously at the dose of 125 mg/kg and orally at the doses of 125 and 250 mg/kg body weight, after which blood and target organs were collected at specified time intervals from 0 to 24 h. HPLC was used to measure the concentration of three major compounds, (6E)-1,7-diphenylhept-6-en-3-one (DPH1), (4E,6E)-1,7-diphenylhepta-4,6-dien-3-ol (DPH2), and (6E)-1,7-diphenylhept-6-en-3-ol (DPH3), which were found to be present in the blood and tissues and were subsequently used as markers. In the intravenous study, the volumes of distribution (V(d)) were 1.06, 8.57, and 6.56 L/kg and clearance values (CL(s)) were 0.28, 5.56, and 3.39 L/kg/h for DPH1, DPH2, and DPH3, respectively. After oral administration, the three major compounds of both doses reached a maximum systemic concentration at 2 h with maximum concentration (C(max)) of 0.85, 0.17, and 0.53 mg/L for the lower dose and 1.46, 0.17, and 0.61 mg/L for the higher dose. The bioavailabilities were 31.2, 24.01, and 31.56% for lower dose and 22.61, 17.66, and 17.73% for higher dose with a terminal half-life (t(1/2)) of 10.86, 6.3, and 4.62 h for lower dose and 3.85, 2.77, and 2.10 h for higher dose for DPH1, DPH2, and DPH3, respectively. These three major compounds are all found distributed in the brain, liver, kidneys, ovaries, and uterus after oral and intravenous administration and their related pharmacokinetic parameters are described. This study provides the essential pharmacokinetic data for diarylheptanoid phytoestrogenic compounds of C. comosa extract which are required for clinical dose and dosage design.