Malate Complex Research Articles

Heteroleptic oxidovanadium(IV)-malate complex improves glucose uptake in HepG2 and enhances insulin action in streptozotocin-induced diabetic rats.

Diabetes mellitus, a complex and heterogeneous disease associated with hyperglycemia, is a leading cause of mortality and reduces life expectancy. Vanadium complexes have been studied for the treatment of diabetes. The effect of complex [VO(bpy)(mal)]·H2O (complex A) was evaluated in a human hepatocarcinoma (HepG2) cell line and in streptozotocin (STZ)-induced diabetic male Wistar rats conditioned in seven groups with different treatments (n = 10 animals per group). Electron paramagnetic resonance and 51V NMR analyses of complex A in high-glucose Dulbecco's Modified Eagle Medium (DMEM) revealed the oxidation and hydrolysis of the oxidovanadium(IV) complex over a period of 24h at 37°C to give low-nuclearity vanadates "V1" (H2VO4-), "V2" (H2V2O72-), and "V4" (V4O124-). In HepG2 cells, complex A exhibited low cytotoxic effects at concentrations 2.5 to 7.5μmol L-1 (IC50 10.53μmol L-1) and increased glucose uptake (2-NBDG) up to 93%, an effect similar to insulin. In STZ-induced diabetic rats, complex A at 10 and 30mgkg-1 administered by oral gavage for 12days did not affect the animals, suggesting low toxicity or metabolic impairment during the experimental period. Compared to insulin treatment alone, complex A (30mgkg-1) in association with insulin was found to improve glycemia (30.6 ± 6.3mmol L-1 vs. 21.1 ± 8.6mmol L-1, respectively; p = 0.002), resulting in approximately 30% additional reduction in glycemia. The insulin-enhancing effect of complex A was associated with low toxicity and was achieved via oral administration, suggesting the potential of complex A as a promising candidate for the adjuvant treatment of diabetes.

Thermo analytical study of phase transformation of TiO2 nanoparticles prepared using mono and di α-hydroxy acid water-soluble precursor by hydrothermal technique

ABSTRACT In this article, the isoconversional crystallization behavior of TiO2 nanoparticles prepared using titanium glycolate and titanium malate water-soluble precursors at alkaline and acidic conditions was investigated. Thermal decomposition experiments were carried out using thermo gravimetric (TG) analysis and the phase structure was determined by powdered X-ray diffraction (PXRD) analysis. The phase stability of the TiO2 NPs prepared using titanium malate complex was found to be better than that prepared using titanium glycolate water-soluble complex, especially in terms of loss in weight per cent and decomposition analysis. Apparent activation energies were also determined for both the samples prepared at pH 2, 4, 6, 8, 10 and 12. These results showed the ability of primary and secondary nucleation in shifting decomposition temperature that in turn increases the phase transformation temperature, by minimizing the energy through fraction reacted required to reach the crystalline state.

295-LB: Metformin Biphasic Effect on Human Cardiac Mitochondria

Mechanisms by which metformin (Mtf) protects human heart in type 2 diabetes remain debated. We hypothesize that Mtf has a biphasic effect on mitochondria: it causes activation of respiration at low doses via AMPK signaling and inhibition at high doses by directly affecting the activity of complex I and reducing oxidative stress. Cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CMs) and mitochondria isolated from human cardiac tissue were exposed to different doses of Mtf (0-20 mM) for 24h and acutely. Oxygen consumption rate (OCR) was assessed in the cells and mitochondria energized by glutamate and malate (complex I substrates) using XF96 Extracellular Flux Analyzer. Superoxide production was measured by monitoring changes in fluorescence intensity of dihydroethidium (DHE). At low doses (0.1 - 1 mM), Mtf significantly increased OCR in hiPSC-CMs (Fig. 1A). The highest OCR was observed at 0.5 mM Mtf. This effect was abrogated by compound C, an inhibitor of AMP-kinase (Fig. 1A). Mtf did not increase OCR in isolated mitochondria (Fig. 1B). At higher doses (1-20 mM), it inhibited OCR both in the cells and isolated mitochondria. This was associated with reduction of superoxide production in the mitochondria (Fig. 1C). In the human heart, Mtf improves cardioprotection due to its biphasic effect on mitochondria. This can be a beneficial alternative to patients with impaired endogenous cardioprotective responses. Disclosure L. Emelyanova: None. X. Bai: None. T. Rudic: None. C. Warner: None. F. Rizvi: None. G. Ross: None. D. Kress: None. A. Jahangir: None. Funding Aurora Health Care (N-570-3657)

Effect of Natural and Artificial Light on Fe(III) Organic Complexes Photolysis: Case of Fe (III)-Malonate and Fe(III)-Malate

Abstract The photolysis of iron(III) organic complexes in the presence of natural and simulated light was a concern for the role it plays within the environment in terms of producing hydroxyl radicals able to degrade organic products. In the present work, the study focused on two iron(III) organic complexes. The characterization of these complexes by spectrometry allowed to show their stability in environment with a stability constant equal to Log β = 13.13 for the complex Fe(III)-malonate, and Log β = 20.85 for the Fe(III)-malate complex. Photolysis of these complexes was carried out using a lamp at 365 nm at different pHs, and followed by several assay Fe(II), H2O2 and •OH. The complexes present different photo-reactivities, in the case of Fe(III)-malate, the photolysis is favored by the Fenton process and generates hydroxyl radicals, contrarily to Fe(III)-malonate photolysis which generates an oxidizing •CH2COOH radical without formation of H2O2 nor of •OH. The presence of oxygen and the addition of isopropanol and chloroform show different effects on the complex photolysis. Complexes mineralization at natural irradiation was also studied using chemical oxygen demand (COD).

Formation of Metal Complexes with Malate Anions: Quantum-Chemical Modeling

Quantum-chemical modeling of anionic forms of malic acid H2mal and the model complex [VV(O)2(mal)]– in which the mal2– ligand is coordinated to the metal ion through its carboxyl and hydroxyl oxygen atoms has been performed by the DFT M06/631G(d,p) method. It has been demonstrated that the participation of the hydroxyl group, which loses its proton only in an alkaline medium, in the formation of malate complexes in an acidic medium is not due to its acid dissociation, but to the process of competitive replacement by a more electropositive metal ion. Calculations show that the simultaneous absence of the protons at the carboxyl and hydroxyl groups leads to electron excess in the region of the –CH2–CHO– bonding. The formation of bonds with electropositive metal ions decreases the electron density in this region, which results in the stabilization of the doubly charged anion.

Thermodynamic and Structural Studies on the Ln(III)/An(III) Malate Complexation.

The complexation of the trivalent lanthanides Nd(III) and Eu(III) and of the actinide Am(III) with malate was studied using a multi-method approach. The combination of structural and thermodynamic studies was required for the interpretation of the stoichiometry and thermodynamic data (log β0, Δr H0m, Δr S0m, Δr G0m) of the lanthanide/actinide malate complexes leading to a profound molecular understanding of the system. The structure-sensitive methods vibrational spectroscopy and extended X-ray absorption fine structure spectroscopy complemented with quantum-mechanical ab initio molecular dynamics calculations revealed a tridentate ring structure of the respective metal complexes. The metal is coordinated by two carboxylate groups and a hydroxyl group. UV-vis, laser fluorescence, and calorimetric studies consistently yielded two complex species having a 1:1 and a 1:2 (metal/malate) stoichiometry. Parallel factor analysis and iterative transformation factor analysis were applied to decompose experimental spectra into their single components and to determine stability constants. The 1:1 and 1:2 Nd(III) malate complexation constants determined by isothermal titration calorimetry were extrapolated to zero ionic strength using the specific ion interaction theory, yielding log β10 and log β20 of about 6 and 9, respectively. The respective complexation enthalpies Δr H0m,1 and Δr H0m,2 showed average values of 5 kJ·mol-1 which are typical for small organic molecules. The comparison of Nd(III) and Am(III) malate complexes showed that the malate binding motif, the speciation, and the thermodynamics can be transferred from lanthanides(III) to actinides(III) supporting the 4f/5f element homology.

Effects of organic acids on uptake of nutritional elements and Al forms in Brassica napus L. under Al stress as analyzed by 27Al-NMR

Hydroponic experiments were performed to investigate the effects of exogenous organic acids on Al accumulation and Al forms in two rape genotypes, Heza No. 7 (Al-tolerant) and Zhongnongyou No. 6 (Al-sensitive) under Al stress. Results showed there exhibited diverse effects on different varieties of rape. Citrate can significantly improve the absorption of Al in Heza No. 7. Al content in Al + citrate increased by 50 % compared with single-Al treatment. In Zhongnongyou No. 6, the highest Al content was observed under mixed treatment with citrate and malate. Organic acids significantly promoted the absorption of Mg, Ca, K, and Fe in roots of Zhongnongyou No. 6, but there were fewer effects on elemental absorption by Heza No. 7. Al-NMR results showed that Al in rape root mainly existed in the form [AlO4Al12(OH)24(H2O)12]7+, with a chemical shift of about 63 ppm. Upon addition of exogenous organic acids, Al mainly existed as non-phytotoxic forms of Al–citrate and Al–malate complexes and showed fewer Al–F complex, Al(OH) 2 4+ , and Al(OH) 2 4+ species. This finding can explain why rape root accumulates large amounts of Al upon treatment with exogenous organic acids but shows no serious toxicity symptoms. We thus conclude that Al–citrate and Al–malate play important roles during Al detoxification in rape.

Degradation of trimethoprim antibiotic by UVA photoelectro-Fenton process mediated by Fe(III)–carboxylate complexes

A UVA photoelectro-Fenton (PEF) process mediated by Fe(III)–carboxylate complexes was applied to the removal of trimethoprim (TMP) antibiotic from water using a 2.2L lab-scale flow plant equipped with a double compound parabolic collector (CPC) and an electrochemical cell composed of a boron-doped diamond (BDD) anode and a carbon–PTFE air-diffusion cathode. The presence of Fe(III)–carboxylate complexes enhances the regeneration of Fe3+ to Fe2+, allows to maintain iron in solution at higher pH values and can decrease the formation of Fe(III)–sulfate, Fe(III)–chloride and some Fe(III)–pollutants complexes. First, the efficiency of different carboxylate ligands like oxalate, citrate, tartrate and malate was assessed, followed by the application of various initial Fe(III)-to-carboxylate molar ratios and pH values. The PEF process with Fe(III)–oxalate, Fe(III)–citrate and Fe(III)–tartrate complexes revealed similar ability to degrade the antibiotic solution with the employment of 1:3, 1:1 and 1:1 Fe(III)-to-carboxylate molar ratios, respectively, and using pH of 4.5, Fe3+ concentration of 2.0mgL−1 (total iron emission limit for the discharge of treated effluents according to the Portuguese legislation), current density of 5mAcm−2 and 20°C. The PEF process mediated by Fe(III)–malate complexes was much less effective. 1:6 and 1:9 Fe(III)-to-oxalate molar ratios were required to yield similar TMP removal kinetics at pH 5.0 and 5.5 compared to pH 4.5, respectively. Additionally, the influence of initial TMP content and solution temperature on the PEF process with Fe(III)–carboxylate complexes was assessed and the role of the different reactive oxidizing species was clarified by the addition of scavenging agents. Generated low-molecular-weight carboxylic acids were monitored by ion-exclusion HPLC.

Photoredox of Cr(III)–Malate Complex and Its Impacting Factors

The transformation of less toxic Cr(III) species to harmful Cr(VI) is worth concerning. Compared with free Cr(III), however, the photo-oxidation of Cr(III)–organic acid complexes is seldom reported. In this study, Cr(III)–malate complex was synthesized and purified, and its photo-oxidation was investigated to reveal the potential conversion pathway of Cr(III) to Cr(VI). The results indicated that Cr(III)–malate complex could be gradually photo-oxidized to Cr(VI) through a ligand–metal charge transfer path. Higher pH and stronger light intensity promoted the conversion process. A 50-μM Cr(III)–malate complex was almost completely oxidized to Cr(VI) within 420-min irradiation of 500 W medium-pressure mercury lamp at pH 12. The introduction of H2O2, considered as a direct source of hydroxyl radicals (·OH) in the presence of Cr(II), markedly enhanced the yield of Cr(VI), and a complete oxidation of Cr(III)–malate complex (50 μM ) was realized within 20 min. Under a weak acidic condition, the production of Cr(VI) was coupled with the reduction of Cr(VI) by malic acid and its free radical generated from Cr(III)–malate complex, leading a gradual decrease in Cr(VI) concentration with the reaction.

Spectroscopic and calorimetric investigation of interaction of chromium(III) malate complex with human serum albumin and apo-transferrin

Spectroscopic and calorimetric investigation of interaction of chromium(III) malate complex with human serum albumin and apo-transferrin

Kinetic studies of the oxidation of transition metal(II) malate complexes by peroxomonosulphate

The kinetics of oxidation of malic acid by peroxomonosulphate (PMS) in the presence of Cu(II) (2.50 × 10−4–5.00 × 10−3 M), Co(II) (2.00 × 10−6–1.00 × 10−5 M) and Ni(II) (5.00 × 10−4–6.00 × 10−3 M) were studied in the pH range 4.05–5.89. The oxidation of Ni(II) malate follows simple first-order kinetics with respect to both [PMS] and [Ni(II)], while the oxidations of Cu(II) malate and Co(II) malate show autocatalysis. There is an appreciable induction period in the Cu(II) malate oxidation, while Co(II) malate oxidation follows a simple curve. The initial oxidation product for all three systems was identified as malonic semialdehyde. Alcohol quenching studies suggest that, even in the Co(II) malate-PMS system, no radical intermediates such as $$ {\text{SO}}_{4}^{ - .} $$ or $$ {\text{OH}}{}^{.} $$ are detected. The malonic semialdehyde intermediate may react with M(II) malates to give a hemiacetal, which may be more reactive.

Enhanced Anti-Diabetic Activity of a Combination of Chromium(III) Malate Complex and Propolis and its Acute Oral Toxicity Evaluation

In order to obtain the additional benefit of anti-diabetic activity and protective effects of liver injury for diabetes, the anti-diabetic effect and acute oral toxicity of a combination of chromium(III) malate complex (Cr(2)(LMA)(3)) and propolis were assessed. The anti-diabetic activity of the combination of the Cr(2)LMA(3) and propolis was compared with Cr(2)(LMA)(3) and propolis alone in alloxan-induced diabetic mice by daily oral gavage for a period of 2 weeks. Acute oral toxicity of the combination of the Cr(2)LMA(3) and propolis was tested using ICR mice at the dose of 1.0-5.0 g/kg body mass by a single oral gavage and observed for a period of 2 weeks. The results of the anti-diabetic activity of the combination from the aspects of blood glucose level, liver glycogen level, and the activities of aspartate transaminase, alanine transaminase, and alkaline phosphatase indicated that the increased anti-diabetic activity and the protective efficacy of liver injury for diabetes were observed. In acute toxicity study, LD(50) (median lethal dose) value for the combination was greater than 5.0 g/kg body mass. The combination of Cr(2)LMA(3) and propolis might represent the nutritional supplement with potential therapeutic value to control blood glucose and exhibit protective efficacy of liver injury for diabetes and non-toxicity in acute toxicity.

Anti-hyperglycemic Activity of Chromium(III) Malate Complex in Alloxan-Induced Diabetic Rats

The synthesis, characterization, anti-hyperglycemic activity, oxidative DNA damage capacity, and acute toxicity of chromium(III) malate complex [Cr2(LMA)3] were described. [Cr2(LMA)3] was synthesized in a single-step reaction by chelating chromium(III) with L-malic acid in aqueous solution. Based on elemental analysis, thermodynamic analysis, and spectroscopy studies, the molecular formula of [Cr2(LMA)3] was inferred as Cr2(C4H4O5)3·5H2O. Daily treatment with 2.85-17.10 mg/kg body mass of [Cr2(LMA)3] in alloxan-induced diabetic rats for 2 weeks indicated that low-molecular-weight organic chromium complex [Cr2(LMA)3] had better bioavailability and more beneficial influences on the improvement of controlling blood glucose, serum lipid, and liver glycogen levels compared with CrCl3·6H2O. [Cr2(LMA)3] did not cause oxidative DNA damage under physiologically relevant conditions. Acute toxicity studies revealed no-measurable toxicity of the [Cr2(LMA)3]. Collectively, these results suggest that [Cr2(LMA)3] may represent a novel, proper chromium supplement with potential therapeutic value to control blood glucose and serum lipid in diabetes.

Iron(III)‐Complexes Engaged in the Biochemical Processes in Seawater. II. Voltammetry of Fe(III)‐Malate Complexes in Model Aqueous Solution

AbstractCharacteristics of iron(III) complexes with malic acid in 0.55 mol L−1 NaCl were investigated by voltammetric techniques. Three iron(III)‐malate redox processes were detected in the pH range from 4.5 to 11: first one at −0.11 V, second at −0.35 V and third at −0.60 V. First process was reversible, so stability constants of iron(III) and iron(II) complexes were calculated: log K1(FeIII(mal))=12.66±0.33, log β2(FeIII(mal)2)=15.21±0.25, log K1(FeII(mal))=2.25±0.36, and log β2(FeII(mal)2)=3.18±0.32. In the case of second and third reduction process, conditional cumulative stability constants of the involved complexes were determined using the competition method: log β(Fe(mal)2(OH)x)=15.28±0.10 and log β(Fe(mal)2(OH)y)=27.20±0.09.

Re-evaluating the effects of organic ligands on copper toxicity to barley root elongation in culture solution

In the presence of weak ligands, both free ion activity and organic complexes of Cu should b considered when predicting Cu toxicity in aquatic and soil-plant systems. However, there is littl information about the quantitative contribution of Cu that is organically complexed to Cu toxicity. In thi study, a bioassay using barley root elongation in culture solution was used to investigate the effects o organic ligands with different conditional stability constants on Cu toxicity and the quantitativ contribution of the organically complexed Cu to the Cu toxicity. The results indicated that a significan decrease (p<0.05) in Cu toxicity, assessed by barley root elongation, was observed in response to th addition of organic ligands. The decrease differed, to some extent, with different organic ligands o disodium ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), oxalate and malate at low and constant free Cu2+ activity. Addition of EDTA or NTA resulted in strong reduction of Cu toxicity while modest reduction of Cu toxicity was observed for the addition of malate as the relatively wea ligand. Furthermore, the results of the present study revealed that the CuNTA− and CuEDTA2− complexes were not toxic, while the Cu–malate complexes were mildly toxic to barley root elongation More importantly, it was found that the toxicity of Cu–malate complexes were nearly 0.5-fold less than that of free Cu2+ ions.

PH and molar ratio dependent formation of monomeric, dimeric and tetrameric cobalt malate complexes

The reactions of cobalt(II) chloride with racemic malic acid (H 3mal = C 4H 6O 5) result in the isolation of monomeric, dimeric and tetrameric cobalt malato complexes: (NH 4) 2[Co( R-Hmal)( S-Hmal)] · 2H 2O ( 1), [Co 2( R-Hmal)( S-Hmal)(H 2O) 4] n · 2 nH 2O ( 2), K 4[Co 4(OH) 2( R-mal) 2( S-mal) 2(H 2O) 4] · 10H 2O ( 3) and trans-[Co( R-H 2mal)( S-H 2mal)(H 2O) 2] · 2H 2O ( 4). The formations of the malato complexes are dependent on the pH value, the molar ratio of the solutions, the reaction temperature and the counterions. In the water-soluble compound 1, the Co II ion is octahedrally coordinated by two tridentate malates via their α-hydroxy, α-carboxy and β-carboxy groups. The malate ligands in 2 coordinate with the cobalt ion via their α-hydroxy and α-carboxy groups, while the β-carboxy group acts as a bridging ligand for the other two cobalt ions, forming a novel dimeric unit [Co 2( R-Hmal)( S-Hmal)(H 2O) 4], which further connects into a layered structure through links from the oxygen atoms of the β-carboxy groups. Complex 3 is a tetranuclear mixed-valence species. Both of the Co II ions exist in trans-[Co( R-mal)( S-mal)(H 2O) 2] units, which are linked by a Co III 2(OH) 2 unit with bridging α-alkoxy and β-carboxy groups. Compound 4 is the main product of reaction between cobalt chloride and excess malate under weakly acidic conditions.

Syntheses, spectroscopies and structures of zinc complexes with malate

Reactions of zinc(II) ion with racemic malic acid (C 4H 6O 5 = H 3mal) result in the isolation of four new zinc(II) malato complexes: (NH 4)[Zn( R-H 2mal) 3] · H 2O ( 1), trans-[Zn( R-H 2mal)( S-H 2mal)(H 2O) 2] · 2H 2O ( 2), (NH 4) 2[Zn( R-Hmal)( S-Hmal)] · 2H 2O ( 3), and [Zn 2( R-Hmal)( S-Hmal)(H 2O) 4] n · 2 nH 2O ( 4). Three R-malic acids in 1 act as bidentate ligands via their alcoholic and the central carboxy groups with Zn(II) ion, leaving the terminal carboxylic acid groups free. The R- and S-malates of 2 coordinate in a bidentate manner with zinc ion in trans-form. In 3, Zn(II) ion is coordinated by R- and S-malates in a tridentate fashion via their alcoholic and two carboxy groups. Complex 4 forms a two-dimensional layered structure through the links of a new dimeric unit [Zn 2( R-Hmal)( S-Hmal)(H 2O) 4] with one of the oxygen atoms from the terminal carboxy group of malate ligand. The coordination of malates depends on pH variation, on Zn:malate ratio, and also on temperature. Tridentate chelation of malate in 3 is found between pH 4.5–9.0. The soluble monomeric species 1– 3 have been investigated using 13C NMR spectra by long-time acquisition. The solution NMR spectra indicate that zinc malate complexes dissociate in H 2O (D 2O). Obvious downfield shifts of the central carboxy carbon atoms in 1– 3 are observed compared with those of free malate, which indicate that these zinc malate complexes dissociate in aqueous solution.

Separation and characterization of aluminium malate species by ion chromatography

Aluminium malate complexes have a high relevance in biological systems. The anionic species present in an aqueous aluminium malate mixture can be investigated by ion chromatography coupled online with inductively coupled plasma atomic emission spectroscopy. As malic acid is a chiral ligand, the experiments were carried out using the racemic and the enantiopure forms. In both systems four anionic complexes are observable in the model solutions. One of two crystallized and well-characterized anions, [Al(4)Malate(6)](6-) and [Al(4)Malate(4)](2-), serves as a reference anion for the assignment of one of the species occurring in the model solutions. The main species in the enantiopure aluminium malate model with biological relevance over a wide pH range is the [Al(4)Malate(4)](2-) anion. The [Al(4)Malate(6)](6-) anion is not present in the racemic model solution. This anion suffers complete species disintegration after dissolution. The kinetics of the decay is first order and the activation energy of the decomposition is 74 kJ/mol. A retention model for ion chromatography was used for the determination of the effective charges of the species. The effective charge obtained by the retention model was calibrated in relation to nominal charges of the anions by using several well-defined and differently charged anions and anionic aluminium species.

Synthesis and Structural Characterization of Two Aluminium Malate Complexes

AbstractThe crystalline aluminium‐malate‐complex, (NH4)6[Al4(D‐C4H3O5)3(L‐C4H3O5)3]·6H2O (1), can be isolated from solutions containing a ratio of 1:2 aluminium to DL‐malic acid in a pH‐range of 5–6. Complex 1 crystallizes in space group $P{\bar 1}$, with a = 9.974(1) Å, b = 10.721(1) Å, c = 12.332(1) Å, α = 102.51(1)°, β = 112.16(1)°, γ = 104.44(1)°, V = 1109.5(2) Å3, and Z = 1. A second crystalline aluminium‐malate‐complex, (C3N2H5)2[Al4(L‐C4H3O5)4(OH)2 (H2O)4]·7H2O (2b), is available from solutions with pH 3 containing a ratio of 1:1 aluminium to L‐malic acid. Complex 2b crystallizes in space group P21, with a = 7.7596(5) Å, b = 25.290(1) Å, c = 10.5393(7) Å, β = 104.855(5)°, V = 1999.1(2) Å3, and Z = 2. A third structure with the same complex anion as it was found in complex 2a is available using aqueous ammonia for pH‐adjustment. The presence of pronounced disorder affecting the positions of the nitrate ion and solvent molecules prohibited a complete structure determination in this case. The two new crystallized complex anions can be used as a powerful tool for aluminium speciation with malic acid ligands. The solution chemistry of the dissolved malate complexes is investigated by NMR spectroscopy.

Cerium isotope effects in Ce(III) malate and lactate complex formation studied by long-distance displacement chromatography

Isotope effects of cerium were observed in malate and lactate complex formations during the long-distance displacement chromatographic processes at 313 K. Heavier isotopes were found fractionated in the frontal edges of the Ce adsorption bands in both the systems, registering a preference of the heavier isotopes for the Ce(III) complexes in the solution phase over the simply hydrated Ce(III) ions in the resin phase. The fractionation coefficients ϵ for the 136Ce/140Ce, 138Ce/140Ce and 142Ce/140Ce isotopic pairs were 7.1 × 10−6, 5.2 × 10−6 and −2.1 × 10−6 for the malate system, and 4.8 × 10−6, 4.5 × 10−6 and−2.6×10−6 for the lactate system, respectively. They all show the mass-dependent law if the deviation of ϵ for the 138Ce/140Ce pair was considered merely due to the isobaric interference in Ce isotopic ratio measurements, suggesting the molecular vibration, rather than the nuclear field shift, mainly contributes to the Ce isotope effects in the complex formation systems. The absolute values of ϵ between the two systems are comparable, suggesting no instinct difference in structural properties between Ce malate and lactate complexes involved. Revised version of a paper presented at the International Conference ‘Isotope 2005 Bath’, 27 June to 1 July 2005, Bath, UK.