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  • Molecularly imprinted polymers for cleanup and selective extraction of curcuminoids in medicinal herbal extracts.

Molecularly imprinted polymers for cleanup and selective extraction of curcuminoids in medicinal herbal extracts.

Analytical and bioanalytical chemistry (2014-07-25)
Meyliana Wulandari, Javier L Urraca, Ana B Descalzo, M Bachri Amran, Maria C Moreno-Bondi
ABSTRACT

This paper describes the synthesis of novel molecularly imprinted polymers (MIPs), prepared by a noncovalent imprinting approach, for cleanup and preconcentration of curcumin (CUR) and bisdemethoxycurcumin (BDMC) from medicinal herbal extracts and further analysis by high-performance liquid chromatography with fluorescence detection (HPLC-FLD). Two molecular mimics, a mixture of reduced BDMCs and 4-(4-hydroxyphenyl)-2-butanone (HPB), have been synthesized and applied as templates for MIP synthesis. The polymers were prepared using N-(2-aminoethyl) methacrylamide (EAMA) as functional monomer, ethylene glycol dimethacrylate (EDMA) as the cross-linker (in a 1:5 molar ratio), and a mixture of acetonitrile/dimethylsulfoxide (90%, v/v) as porogen. MIPs prepared using a mixture of reduced BDMCs as template showed higher selectivity for CUR and BDMC than those obtained with HPB, with imprinting factors of 3.5 and 2.7 for CUR and BDMC, respectively, using H2O/acetonitrile (65:35, v/v) as mobile phase. The adsorption isotherms for CUR in the MIP and the nonimprinted polymer (NIP) were fitted to the Freundlich isotherm model, and the calculated average binding affinities for CUR were (17 ± 2) and (8 ± 1) mM(-1) for the MIP and the NIP, respectively. The polymers were packed into solid-phase extraction (SPE) cartridges, and the optimized molecularly imprinted solid-phase extraction (MISPE-HPLC) with fluorescence detection (FLD) method allowed the extraction of both curcuminoids from aqueous samples (50 mM NH4Ac, pH 8.8) followed by a selective washing with acetonitrile/NH4Ac, 50 mM at pH 8.8 (30:70%, v/v), and elution with 3 × 1 mL of MeOH. Good recoveries and precision ranging between 87 and 92%, with relative standard deviation (RSD) of <5.3% (n = 3), were obtained after the preconcentration of 10-mL solutions containing both CUR and BDMC at concentrations in the range of 0-500 μg L(-1). The optimized method has been applied to the analysis of both curcuminoids in medicinal herbal extracts.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Hydrogen chloride solution, 3 M in cyclopentyl methyl ether (CPME)
Sigma-Aldrich
Methanol, NMR reference standard
USP
Dehydrated Alcohol, United States Pharmacopeia (USP) Reference Standard
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Resorcinol, BioXtra, ≥99%
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Bisdesmethoxycurcumin, United States Pharmacopeia (USP) Reference Standard
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Hydrochloric acid solution, 32 wt. % in H2O, FCC
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Resorcinol, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
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Tetrabutylammonium hydroxide solution, 53.5-56.5% in H2O
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4-(4-Hydroxyphenyl)-2-butanone, 99%
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Ammonium acetate, LiChropur, eluent additive for LC-MS
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Resorcinol, meets analytical specification of Ph. Eur., BP, 98.5-100.5% (calc. to the dried substance)
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Tetrabutylammonium hydroxide solution, ~40% in water, suitable for ion chromatography
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Hydrogen chloride – methanol solution, ~1.25 m HCl (T), for GC derivatization, LiChropur
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Tetrahydrofuran, Selectophore, ≥99.5%
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Ammonium acetate solution, BioUltra, for molecular biology, ~5 M in H2O
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Ammonium acetate, 99.999% trace metals basis
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Ethanol solution, certified reference material, 2000 μg/mL in methanol
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4-(4-Hydroxyphenyl)-2-butanone, natural, ≥98%, FCC, FG
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4-(4-Hydroxyphenyl)-2-butanone, ≥98%, FCC, FG
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Valeronitrile, 99.5%
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Tetrabutylammonium hydroxide solution, 1.0 M in methanol
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Tetrabutylammonium hydroxide solution, 40 wt. % in H2O
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Resorcinol, ≥98%, FG
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Ammonium acetate, BioUltra, for molecular biology, ≥99.0%
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Hydrochloric acid solution, volumetric, 0.1 M HCl (0.1N), endotoxin free
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Hydrochloric acid solution, 1.0 N, BioReagent, suitable for cell culture