Simultaneous determination of curcumin diethyl disuccinate and its active metabolite curcumin in rat plasma by LC-MS/MS: Application of esterase inhibitors in the stabilization of an ester-containing prodrug

Validated HPLC method for simultaneous quantitative determination of dimethylcurcumin and resveratrol in pluronic-F127 nanomicelles: Formulation with enhanced anticancer efficacy

Nano-micelles offer a promising vehicle for the delivery various therapeutically significant biologicals. Development of convenient and efficient chromatographic methods for the quantitative determination of the active pharmaceutical ingredients in such systems is of immense importance. In this study pluronic-F-127 nano-micelles were prepared and loaded with dimethylcurcumin (DMC) and resveratrol (Res). A simple, convenient and effective HPLC method was developed for the quantitative estimation of DMC and Res in the polymeric nano-micelles through a single injection. A reverse-phase ACE® C18 column (250 mm × 4.6 mm) was used with a gradient mobile phase system consisting of 1 % MeOH and 0.1 % H3PO4:100 % acetonitrile at 1 mL/min flow rate with UV detection for Res, and fluorescence detector for DMC. The calibration curves generated for both the compounds were found linear with r2 values of 1.000 over a concentration range of 2-25 µg/mL with low limit of detection (LOD) values of 0.37 and 0.16 µg/mL for DMC and Res respectively and limit of quantification (LOQ) values of 1.23 and 0.55 µg/mL for DMC and Res respectively. Similarly, accuracy was found in a range of 98.80 -102.47 % for DMC and 100.58-101.77 % for Res. Furthermore, the within-run precisions (%RSD) were 0.073 - 0.444% for DMC and 0.159 - 0.917% for Res, while between-run precisions (%RSD) were 0.344 - 1.47 for DMC and 0.458 - 1.651 for Res. Moreover, the DMC with Res co-loaded nanomicelles showed higher activity against MCF-7 and MDA-MB 231 compared to DMC and Res alone. Overall, this study presented a simple, convenient, precise and accurate method for the quantitative determination of DMC and Res in polymeric nano-micelles which have anticancer potential.•A simple HPLC for the quantitative determination of DMC and Res in nanomicelles having anti-cancer potential.•Non complicate with high degree of recoveries of sample preparation process.•This method can be used to determine a mixture of DMC and Res in pharmaceutical formulation in single injection.

Development of a rapid, sensitive, and selective LC-MS/MS method for quantifying curcumin levels in healthy human urine: Effect of pepper on curcumin bioavailability

Curcumin (CCM), a culinary spice, is widely consumed for its health benefits for managing oxidative and inflammatory conditions, metabolic syndrome, arthritis, and hyperlipidemia. However, due to its extensive metabolism, the oral bioavailability of CCM is very low. In this study, we developed a rapid, sensitive, and selective assay to examine the hypothesis that piperine improves CCM bioavailability after piperine co-ingestion. We developed a selective, sensitive, and robust LC-MS/MS method to quantify CCM in human urine. The method was linear over a concentration range 0.625-40 ng/mL with LLOQ and LLOD of 0.625 ng/mL and 0.312 ng/mL, respectively. Healthy volunteers have consumed test meals of CCM as turmeric powder with and without black pepper with 1 week wash out. Urine samples were collected for 24 hours and analyzed for CCM excretion. Black pepper increased CCM half-life from 2.2 ± 0.79 h (CCM alone) to 4.5 ± 0.80 h (CCM + pepper). The CCM 24-h urinary excreted amount was higher in individuals consuming CCM + pepper (218.14 ± 94.98 μg) than those who received CCM only (49.45 ± 12.94 μg). This preliminary study indicates that piperine significantly increased CCM oral absorption, reduced systemic clearance, and improved bioavailability.

Pharmacokinetic study of Tdp1 inhibitor resulted in a significant increase in antitumor effect in the treatment of Lewis lung carcinoma in mice by its combination with topotecan

We have previously shown that the Tdp1 inhibitor, enamine derivative of usnic acid, the agent OL9-116, enhances the antitumor activity of topotecan. In the present study, we developed and validated LC-MS/MS method for the quantification of OL9-116 in mouse whole blood and studied pharmacokinetics of the agent. The substance OL9-116 was shown to be stable in the whole blood in vitro. Sample preparation included two steps: mixing 10 µL of a blood sample with 10 µL of 0.2 M ZnSO4 aqueous solution, followed by protein precipitation with 100 µL of acetonitrile containing internal standard. Quantification of the compound was performed using SCIEX 6500 QTRAP mass spectrometer in MRM mode following chromatographic separation on a C8 reversed-phase column. The method was validated in terms of selectivity, linearity, accuracy, precision, recovery, and stability of the prepared sample. When the agent OL9-116 was administered intragastrically at a dose of 150 mg/kg, the maximum concentration in the blood (about 5000 ng/mL) was reached after 2-4 h followed by the distribution and elimination of the compound. A study of the antitumor activity of a combination of OL9-116 and topotecan against Lewis lung carcinoma revealed that administration of topotecan 3 h after OL9-116 resulted in the most pronounced antitumor effect compared to simultaneous or individual administration of both compounds.

Hydrolytic Metabolism of Withangulatin A Mediated by Serum Albumin Instead of Common Esterases in Plasma

BACKGROUND AND OBJECTIVES

The oral bioavailability of withangulatin A (WA) is low and may undergo first-pass metabolism because of the presence of two esters bonds. This study aimed to identify the hydrolysis behavior and mechanism of WA, thus enriching its structure-pharmacokinetic relationship.

METHODS

The in vivo pharmacokinetic studies of WA in rats were first investigated, followed by in vitro assays including metabolic stability, phenotyping identification and metabolic kinetics assays. After screening out the responsible enzymes with higher catalytic capacity, molecular docking study was performed to demonstrate the interaction mode between WA and metabolic enzymes. Then, metabolites in human serum albumin (HSA) were identified by LC-TOF-MS/MS.

RESULTS

In rats, the oral bioavailability of WA was only 2.83%. In vitro, WA was hydrolyzed in both rat and human plasma and could not be inhibited by selective esterase inhibitors. Physiologic concentration of HSA not recombinant human carboxylesterases (rhCES) could significantly hydrolyze WA, and it had a similar hydrolytic capacity with human plasma to WA. Furthermore, WA could stably bind to HSA by forming hydrogen bonds with Lys199 and Arg410, accompanied by the metabolic reaction of the lactone ring opening.

CONCLUSION

The study showed that WA underwent obvious hydrolysis in rat and human plasma, which implied a strong first-pass effect. Serum albumin rather than common esterases primarily contributed to the hydrolytic metabolism of WA in plasma.

Synthesis of N-heterocyclic amides based on (+)-camphoric acid and study of their antiviral activity and pharmacokinetics

Efficient conditions for the synthesis of nitrogen-containing heterocyclic derivatives of (1R,3S)(+)-camphoric acid were selected. A series of heterocyclic compounds based on (+)-camphoric acid bearing pharmacophoric fragments was synthesized using the developed methodology. The compounds were tested for their antiviral activity against SARS-CoV-2 and H1N1 influenza viruses, and efficient inhibitors were identified that are of significant interest for further studies. The stability of the compounds and pharmaco-kinetics of the leader compound were studied when administered intragastrically and intramuscularly to mice at a dose of 200 mg kg^-1 using the HPLC-MS/MS method.

Stability Study, Quantification Method and Pharmacokinetics Investigation of a Coumarin-Monoterpene Conjugate Possessing Antiviral Properties against Respiratory Syncytial Virus

The stability of a new coumarin derivative, agent K-142, bearing α-pinene residue and possessing antiviral activity against respiratory syncytial virus (RSV) was studied in whole mice blood in vitro, and a method for its quantification in this matrix was developed and validated. The sample preparation method was precipitation of whole blood with a mixture of 0.2 M ZnSO₄ with MeOH (2:8 v/v) containing 2-adamantylamine hydrochloride as an internal standard (IS). Analysis was carried out by HPLC-MS/MS using reversed phase chromatography and a triple quadrupole mass spectrometer 6500 QTRAP (SCIEX) in multiple reaction monitoring (MRM) mode. The transitions 351.2 → 217.1 Da and 152.2 → 93.1/107.2 Da were monitored for K-142 and the IS, respectively. The method was validated in terms of selectivity, calibration curve, LLOQ, accuracy and precision, stability, recovery and carry over. The developed method was used for a pharmacokinetics study of the compound after its oral administration to mice at a dose of 20 mg/kg.

Physicochemical investigation of a novel curcumin diethyl γ-aminobutyrate, a carbamate ester prodrug of curcumin with enhanced anti-neuroinflammatory activity

Curcumin is a polyphenol compound that alleviates several neuroinflammation-related diseases including Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy and cerebral injury. However, the therapeutic efficacy of curcumin is limited by its poor physicochemical properties. The present study aimed to develop a new carrier-linked curcumin prodrug, curcumin diethyl γ-aminobutyrate (CUR-2GE), with improved physicochemical and anti-neuroinflammatory properties. CUR-2GE was designed and synthesized by conjugating curcumin with gamma-aminobutyric acid ethyl ester (GE) via a carbamate linkage. The carbamate linkage was selected to increase stability at acidic pH while GE served as a promoiety for lipophilic enhancement. The synthesized CUR-2GE was investigated for solubility, partition coefficient, stability, and bioconversion. The solubility of CUR-2GE was less than 0.05 μg/mL similar to that of curcumin, while the lipophilicity with log P of 3.57 was significantly increased. CUR-2GE was resistant to chemical hydrolysis at acidic pH (pH 1.2 and 4.5) as anticipated but rapidly hydrolyzed at pH 6.8 and 7.4. The incomplete hydrolysis of CUR-2GE was observed in simulated gastrointestinal fluids which liberated the intermediate curcumin monoethyl γ-aminobutyric acid (CUR-1GE) and the parent curcumin. In plasma, CUR-2GE was sequentially converted to CUR-1GE and curcumin within 1 h. In lipopolysaccharide (LPS)-stimulated BV-2 microglial cells, CUR-2GE effectively attenuated the pro-inflammatory mediators by decreasing the secretion of nitric oxide and cytokines (TNF-α and IL-6) to a greater extent than curcumin due to an increase in cellular uptake. Altogether, the newly developed acid-stable CUR-2GE prodrug is a potential pre-clinical and clinical candidate for further evaluation on neuroprotective and anti-neuroinflammatory effects.

Curcumin: Biological Activities and Modern Pharmaceutical Forms

Curcumin (1,7-bis-(4-hydroxy-3-methoxyphenyl)-hepta-1,6-diene-3,5-dione) is a natural lipophilic polyphenol that exhibits significant pharmacological effects in vitro and in vivo through various mechanisms of action. Numerous studies have identified and characterised the pharmacokinetic, pharmacodynamic, and clinical properties of curcumin. Curcumin has an anti-inflammatory, antioxidative, antinociceptive, antiparasitic, antimalarial effect, and it is used as a wound-healing agent. However, poor curcumin absorption in the small intestine, fast metabolism, and fast systemic elimination cause poor bioavailability of curcumin in human beings. In order to overcome these problems, a number of curcumin formulations have been developed. The aim of this paper is to provide an overview of recent research in biological and pharmaceutical aspects of curcumin, methods of sample preparation for its isolation (Soxhlet extraction, ultrasound extraction, pressurised fluid extraction, microwave extraction, enzyme-assisted aided extraction), analytical methods (FTIR, NIR, FT-Raman, UV-VIS, NMR, XRD, DSC, TLC, HPLC, HPTLC, LC-MS, UPLC/Q-TOF-MS) for identification and quantification of curcumin in different matrices, and different techniques for developing formulations. The optimal sample preparation and use of an appropriate analytical method will significantly improve the evaluation of formulations and the biological activity of curcumin.

Thermal desorption bridged the gap between dielectric barrier discharge ionization and dried plasma spot samples for sensitive and rapid detection of fentanyl analogs in mass spectrometry

Guided by finite element simulations and 3D-printing, we constructed a semi-covered flat-TD surface for sufficient thermal desorption and ionization of fentanyl analogs from dried plasma/blood spot samples.

Curcumin as a great contributor for the treatment and mitigation of colorectal cancer

Cancer is one of the life-taking diseases worldwide and among cancer-related death; colorectal cancer is the third most. Though conventional methods of treatment are available, multidrug resistance and side effects are predominant. Physicians and scientists are working side by side to develop an effective medicament, which is safe and cost-effective. However, most failures are obtained when focused on the clinical perspective. This review mainly brings out the correlation between the curcumin and its use for the mitigation of colorectal cancer, the use of curcumin as a chemotherapeutic agent, chemosensitizer, and in a combination and synergistic approach. The pharmacokinetics and pharmacodynamics properties of curcumin and its formulation approach helps in giving an idea to develop new approaches for the treatment of colorectal cancer using curcumin.

Stability of Ketoprofen Methylester in Plasma of Different Species

BACKGROUND

Pharmacokinetic and pharmacodynamic assessment of ester-containing drugs can be impacted by hydrolysis of the drugs in plasma samples post blood collection. The impact is different in the plasma of different species.

OBJECTIVE

This study evaluated the stability of a prodrug, ketoprofen methylester (KME), in commercially purchased and freshly collected plasma of mouse, rat, dog, cat, pig, sheep, cattle and horse.

METHODS

KME hydrolysis was determined following its incubation in commercially purchased and freshly collected plasma of those species. Different esterase inhibitors were evaluated for prevention of the hydrolysis in rat, dog and pig plasma.

RESULTS

KME was rapidly hydrolyzed in both commercially purchased and freshly collected plasma of mouse, rat, and horse. The hydrolysis was initially quick and then limited in cat plasma. KME hydrolysis was minimum in commercially purchased plasma of dog, pig, sheep and cattle but substantial in freshly collected plasma of those species. Different esterase inhibitors showed different effects on the stability of KME in rat, dog and pig plasma.

CONCLUSION

These results indicate that plasma of different species has different hydrolytic activities to estercontaining drugs. The activities in commercially purchased and freshly collected plasma may be different and species-dependent. Esterase inhibitors have different effects on preventing hydrolysis of the ester-containing drugs in the plasma of different species.

Biostability study, quantitation method and preliminary pharmacokinetics of a new antifilovirus agent based on borneol and 3-(piperidin-1-yl)propanoic acid

The stability of the new antifiloviral agent AS-358, which is a derivative of borneol and 3-(piperidin-1-yl)propanoic acid, was studied in the blood and blood plasma of rats in vitro. It was found that both in the blood and in the plasma stabilized by EDTA or heparin, the compound is rapidly hydrolyzed at the ester bond. When sodium fluoride was added to the whole blood, the decomposition of the compound was significantly slowed down, which made it possible to develop and validate a method for the quantitative determination of the agent in this matrix. The method was validated in terms of selectivity, calibration dependence, LLOQ, accuracy and precision, stability in an autosampler, recovery, and carry-over. A 8:2 v/v mixture of methanol containing 2-adamantylamine hydrochloride (internal standard, IS) with 0.2 M aqueous zinc sulfate was used for blood sample treatment and protein precipitation. Analysis was performed by HPLC-MS/MS using reversed phase chromatography. MS/MS detection was performed on a triple quadrupole mass spectrometer 6500 QTRAP (SCIEX) in multiple reaction monitoring (MRM) mode. The transitions 294.5→158.2/98.1 and 152.2→107.2/93.1 were monitored for AS-358 and the IS, respectively. The calibration curve was built in the concentration range of 1-500 ng/mL, the intra-day and inter-day accuracy and precision, carry-over and recovery were within the acceptable limits. The developed method was used for a preliminary study of the pharmacokinetics of the agent AS-358 after its oral administration to rats. It was shown that when the substance was administered at a dose of 200 mg/kg, its concentration in the blood of animals reached 550 ng/mL after 1 h, despite its instability in blood.

Chitosan-alginate nanoparticles as effective oral carriers to improve the stability, bioavailability, and cytotoxicity of curcumin diethyl disuccinate

Curcumin diethyl disuccinate (CDD) is an ester prodrug of curcumin that has better chemical stability in phosphate buffer (pH 7.4) and anticancer activities against MDA-MB-231 human breast cancer cells and Caco-2 cells than curcumin. However, a major drawback of CDD is its poor water solubility and low bioavailability in the gastrointestinal tract. To overcome these problems, a nanoformulation was developed using chitosan/alginate nanoparticles (CANPs) under the optimal condition as previously derived by statistical optimization. The CDD-loaded CANPs (CDD-CANPs) were found to exhibit good stability after exposure to simulated digestive fluids and ultraviolet light, and a sustained-release profile of CDD in the simulated digestive and body fluids. The in vitro release pattern fitted well to the Peppas-Sahlin model, indicating that the release of CDD was mainly governed by diffusion. Compared to free CDD, the CDD-CANPs showed better stability, bioaccessibility, bioavailability, cellular uptake, and cytotoxicity against HepG2 cells.

In Vitro Hepatic Metabolism of Curcumin Diethyl Disuccinate by Liver S9 from Different Animal Species

Liver S9 (LS9) is a nearly complete collection of all hepatic drug-metabolizing enzymes. It is a low-cost model for predicting drug metabolic activity. This study aimed to identify the suitability of using LS9 of different animal sources in drug metabolism profiling with respect to the possible translation of the in vitro outcomes to clinical studies. The in vitro hepatic metabolism of curcumin diethyl disuccinate (CDD) in LS9 of rats, dogs, monkeys, and humans was evaluated. The identity of CDD metabolites and the metabolism kinetic parameters, including degradation rate constant, in vitro/in vivo intrinsic clearance, and half-life, were determined. CDD was rapidly metabolized into monoethylsuccinyl curcumin and curcumin in LS9 of all tested species mainly by carboxylesterases (CESs), including CES1 and CES2, and butyrylcholinesterase. The in vitro intrinsic clearance of CDD was in the order of human > dog > monkey > rat, whereas that of monoethylsuccinyl curcumin in the order of dog > monkey > human > rat; this parameter was not correlated with their respective in vivo clearance, which followed the order of dog > monkey > rat > human. Therefore, in vitro drug metabolism data inferred from LS9 of nonhuman origin, especially from monkeys and dogs, cannot be used as preclinical data for human trials, as humans have a smaller liver-to-body weight ratio than monkeys, dogs, and rats. The in vivo drug metabolism is dictated by the anatomical factors of the test subject.

A stability-indicating UPLC method for the determination of curcumin diethyl disuccinate, an ester prodrug of curcumin, in raw materials

A stability-indicating reversed-phase ultra-performance liquid chromatographic (UPLC) method for quantitative analysis of curcumin diethyl disuccinate (CDD) in raw materials was developed for applications in product development and quality control. Chromatographic separation was performed using the Waters ACQUITY UPLC® H-Class system consisting of an ACQUITY UPLC® BEH C18 (1.7 μm, 2.1 × 50 mm) column and a photodiode array detector set at a wavelength of 400 nm. The mobile phase consisting of 2%v/v acetic acid in water and acetonitrile was delivered at a flow rate of 0.3 mL/min under gradient elution program. The method was validated according to the ICH Q2(R1) guideline for the validation of analytical procedures. The method was found to be linear over the concentration range of 8-12 μg/mL with the coefficient of determination >0.995. The accuracy of the method established as %recovery ranged from 98.3 - 100.8%. The precision of the method expressed as %CV was found to be <1%. The coelution of degradation products from six stress test conditions was not observed. The method was robust under the variation of chromatographic parameters. The method was successfully applied in the determination of CDD content in raw materials.

Curcumin: Biological, Pharmaceutical, Nutraceutical, and Analytical Aspects

Turmeric is a curry spice that originated from India, which has attracted great interest in recent decades because it contains bioactive curcuminoids (curcumin, demethoxycurcumin, and bisdemethoxycurcumin). Curcumin (1,7-bis-(4-hydroxy-3-methoxyphenyl)-hepta-1,6-diene-3,5-dione), a lipophilic polyphenol may work as an anticancer, antibiotic, anti-inflammatory, and anti-aging agent as suggested by several in vitro, in vivo studies and clinical trials. However, poor aqueous solubility, bioavailability, and pharmacokinetic profiles limit curcumin’s therapeutic usage. To address these issues, several curcumin formulations have been developed. However, suboptimal sample preparation and analysis methodologies often hamper the accurate evaluation of bioactivities and their clinical efficacy. This review summarizes recent research on biological, pharmaceutical, and analytical aspects of the curcumin. Various formulation techniques and corresponding clinical trials and in vivo outcomes are discussed. A detailed comparison of different sample preparation (ultrasonic, pressurized liquid extraction, microwave, reflux) and analytical (FT-IR, FT-NIR, FT-Raman, UV, NMR, HPTLC, HPLC, and LC-MS/MS) methodologies used for the extraction and quantification of curcuminoids in different matrices, is presented. Application of optimal sample preparation, chromatographic separation, and detection methodologies will significantly improve the assessment of different formulations and biological activities of curcuminoids.

Curcumin diethyl disuccinate, a prodrug of curcumin, enhances anti-proliferative effect of curcumin against HepG2 cells via apoptosis induction

Curcumin (Cur) has been reported to have anti-hepatocellular carcinoma activity but its poor oral bioavailability limits its further development as a chemotherapeutic agent. We synthesized previously a succinate ester prodrug of Cur, curcumin diethyl disuccinate (CurDD) with better chemical stability in a buffer solution pH 7.4. Here, we further investigated and compared the cellular transport and anti-proliferative activity against HepG2 cells of CurDD and Cur. Transport of CurDD across the Caco-2 monolayers provided a significantly higher amount of the bioavailable fraction (BF) of Cur with better cytotoxicity against HepG2 cells compared to that of Cur (p < 0.05). Flow cytometric analysis showed that the BF of CurDD shifted the cell fate to early and late apoptosis to a higher extent than that of Cur. The Western blot analysis revealed that CurDD increased Bax protein expression, downregulated Bcl-2 protein, activated caspase-3 and -9 and increased LC3-II protein level in HepG2 cells. Flow cytometric and immunoblotting results suggest that CurDD can induce HepG2 cell death via an apoptotic pathway. We suggest that CurDD can overcome the limitations of Cur in terms of cellular transport with a potential for further extensive in vitro and in vivo studies of anti-hepatocellular carcinoma effects.

Scale-Up Synthesis and In Vivo Anti-Tumor Activity of Curcumin Diethyl Disuccinate, an Ester Prodrug of Curcumin, in HepG2-Xenograft Mice

Previously, we synthesized curcumin and a succinate ester prodrug of curcumin namely curcumin diethyl disuccinate (CurDD) in the lab scale, which yielded hundred milligrams to few grams of the compounds. CurDD was found to be more stable in a phosphate buffer pH 7.4 and exhibited better cytotoxicity against Caco-2 cells than curcumin. Here, the one-pot syntheses of curcumin and CurDD were scaled up to afford multigram quantities of both compounds for preclinical studies using a 10-L chemical reactor. The key steps for the synthesis of curcumin were the formation of boron-acetylacetone complex and the decomplexation of boron-curcumin complex. The synthesis of CurDD could be achieved via a one-step esterification between curcumin and succinic acid monoethyl ester chloride using 4-(N,N-dimethylamino)pyridine as a catalyst. The synthesized curcumin and CurDD were then investigated and compared for an anti-tumor activity in HepG2-xenograft mice. CurDD could reduce the tumor growth in HepG2-xenograft mice better than curcumin. CurDD also exerted the stronger inhibition on VEGF secretion, COX-2 and Bcl-2 expression and induced higher Bax expression in comparison with curcumin. The results suggest that CurDD is a promising prodrug of curcumin and has a potential to be further developed as a therapeutic agent or an adjuvant for the treatment of hepatocellular carcinoma.

Interspecies differences in stability kinetics and plasma esterases involved in hydrolytic activation of curcumin diethyl disuccinate, a prodrug of curcumin

The investigation of in vitro plasma metabolism of ester prodrugs is an important part of in vitro ADME assays during preclinical drug development. Here, we show that the in vitro metabolism including plasma stability and metabolizing enzymes of curcumin diethyl disuccinate (CDD), an ester prodrug of curcumin, in dog and human plasma are similar but markedly different from those in rat plasma. HPLC and nonlinear regression analyses indicated that the hydrolysis of CDD in plasma followed a consecutive pseudo-first order reaction. The rapid hydrolytic cleavage of CDD in rat, dog, and human plasma was accelerated by plasma esterases in the following order: rat ≫ human > dog. LC-Q-TOF/MS analysis showed that the cleavage of ester bonds of CDD is preferential at the phenolic ester. Monoethylsuccinyl curcumin is the only intermediate metabolite found in plasma metabolism of CDD in all tested species. Further investigation using different esterase inhibitors revealed that carboxylesterase is the major enzyme involved in the hydrolysis of CDD in rats while multiple plasma esterases play a role in dogs and humans. Thus, the difference in the hydrolysis rates and the metabolizing enzymes of CDD metabolism in rat, dog and human plasma observed here is of benefit to further in vivo studies and provides a rationale for designing ester prodrugs of CUR with esterase-specific bioactivation.

Curcumin diethyl disuccinate is metabolized at different rates and hydrolyzed by different esterases in rat, dog and human plasma.

A Novel Triple Stage Ion Trap MS method validated for curcumin pharmacokinetics application: A comparison summary of the latest validated curcumin LC/MS methods

Even through more sensitive methods for quantifying trace levels of curcumin in plasma were urgently needed, beyond tandem mass spectrometry, the Paul trap MS/MS/MS has never been tested for curcumin quantification. Because of its unique trap function to accumulate target compounds selectively by optimizing multiple stage MS experiments, it showed great potential to remove background issues reported at low concentration ranges. A novel Triple stage Ion Trap Mass Spectrometry coupled with High Performance Liquid Chromatography (HPLC-ITMS/MS/MS) method has been developed and validated as a curcumin quantification method, for the first time. The use of isotope labeled curcumin-d6 as a novel internal standard (IS) is suggested and tested according to FDA validation procedure. A simplified sample preparation is introduced and validated by coupling a novel acetonitrile precipitation with molecular weight cut-off size exclusion method. This method demonstrated excellent recovery rate of 96.69%-109.26% and minimum matrix effect of 95.40%-110.98%. The lower limit of detection (LLOD) and lower limit of quantification (LLOQ) for curcumin in rat plasma were 0.1 ng/ml and 1 ng/ml respectively. The linear calibration curve for quantifying curcumin in rat plasma was 1-3000 ng/ml (r² > 0.99) with intra-day and inter-day RSD and accuracy within ±5.11%. Its application in a Pharmacokinetics (PK) study demonstrated detection of curcumin at a very low plasma level (1.0 ng/ml) and it would be applied to larger sample size animal and clinical pharmacokinetic studies. The presented ITMS/MS/MS quantification method has shown its advantages, including better sensitivity, accuracy, precision, wider calibration range and simplicity in sample preparation, when comparing with other curcumin LC/MS analysis methods in the latest 4 years.

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

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