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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
4-(4-Hydroxyphenyl)-2-butanone, ≥98%, FCC, FG
Supelco
Ethanol solution, certified reference material, 2000 μg/mL in methanol
Sigma-Aldrich
Bisdemethoxycurcumin, ≥98% (HPLC), solid
Sigma-Aldrich
Methanol, NMR reference standard
USP
Resorcinol, United States Pharmacopeia (USP) Reference Standard
USP
Bisdesmethoxycurcumin, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
Methanol, ACS reagent, ≥99.8%
Sigma-Aldrich
Methanol, suitable for HPLC, gradient grade, ≥99.9%
Sigma-Aldrich
Methanol, suitable for HPLC, gradient grade, suitable as ACS-grade LC reagent, ≥99.9%
Resorcinol, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Methanol, puriss., meets analytical specification of Ph Eur, ≥99.7% (GC)
Sigma-Aldrich
Hydrogen chloride solution, 1.0 M in acetic acid
Sigma-Aldrich
Hydrogen chloride solution, 1.0 M in diethyl ether
Sigma-Aldrich
Tetrahydrofuran, contains 250 ppm BHT as inhibitor, puriss. p.a., ACS reagent, reag. Ph. Eur., ≥99.9%
Sigma-Aldrich
Hydrochloric acid, ACS reagent, 37%
Sigma-Aldrich
Hydrochloric acid, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., fuming, ≥37%, APHA: ≤10
Sigma-Aldrich
Methanol, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.8% (GC)
Sigma-Aldrich
Hydrochloric acid, 37 wt. % in H2O, 99.999% trace metals basis
Sigma-Aldrich
Hydrogen chloride solution, 2.0 M in diethyl ether
Sigma-Aldrich
Hydrochloric acid, meets analytical specification of Ph. Eur., BP, NF, fuming, 36.5-38%
Sigma-Aldrich
Hydrochloric acid, puriss., 24.5-26.0%
Supelco
Residual Solvent - Acetonitrile(solution in DMSO), Pharmaceutical Secondary Standard; Certified Reference Material
Hymecromone impurity A, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Methanol, anhydrous, 99.8%
Supelco
Tetrahydrofuran, HPLC grade, ≥99.9%, inhibitor-free
Sigma-Aldrich
4-(4-Hydroxyphenyl)-2-butanone, natural, ≥98%, FCC, FG
Sigma-Aldrich
Resorcinol, ≥98%, FG
Sigma-Aldrich
Tetrahydrofuran, anhydrous, ≥99.9%, inhibitor-free
Sigma-Aldrich
4-(4-Hydroxyphenyl)-2-butanone, 99%
Supelco
Hydrogen chloride – ethanol solution, ~1.25 M HCl, for GC derivatization, LiChropur