Nuclear magnetic resonance analysis of extra virgin olive oil: classification through secoiridoids

BACKGROUND

Extra virgin olive oil (EVOO), a natural product with a multidisciplinary role, has been and is continuing to be studied from several points of view. Among them, its chemical analysis is of major importance and several methods have been used. Nuclear magnetic resonance (NMR) spectroscopy has inherent advantages, among them monitoring the chemical constituents without the need for a separation technique and without, for instance, possible carry-over effects. Additionally, several magnetic resonance spectroscopic techniques can provide a novel powered insight into the nature and properties of a sample under study. Moreover, -omics procedure can reveal new information and can lead to the classification of populations under study. The main objective of the present work was the possible classification of the EVOO samples based on their aldehyde content using a proposed unreferenced 1 H-NMR spectroscopic quantification method combined with a metabolomic approach. Moreover, the study of the impact of such elevated aldehyde content on several spectra regions of importance in the proton NMR spectra led to the proposal of a possible new isomer indicator.

RESULTS

Univariate analysis of 12 EVOO samples showed that oleacein, oleocanthal, elenolic acid, hydroxytyrosol/hydroxytyrosol derivatives and tyrosol/tyrosol derivatives strongly differentiated two classes of EVOO: OEH (for high aldehyde EVOO content) and OE (for non-high aldehyde content). Moreover, we pointed out the 'impact' of such elevated secoiridoid and derivatives content, through their moieties' units, on a range of several resonances of the 1 H-NMR spectrum. The metabolomic approach demonstrated the classification of EVOO samples based on their secoiridoid and derivatives content. Multivariate analysis showed a strong influence on the discrimination of the EVOO classes based on the protons resonating at the aldehyde region of the 1 H-NMR spectrum; the aldehyde protons corresponding to 5S,4R-ligstrodial and 5S,4R-oleuropeindial, oleacein, oleocanthal, elenolic acid, p-HPEA-EA, 3,4-DHPEA-EA, 5S,4R- and 5S,4S-ligstrodial and the proton corresponding to a new compound were reported for the first time. This isomer compound, reported for the first time, could serve as a possible indicator for EVOO classification.

CONCLUSIONS

An unreferenced quantification method was proposed and EVOO samples were classified into two classes: OEH and OE, according to their aldehyde content, gaining thus probably higher nutrient and possible pharmacological value. Moreover, we point out the 'impact' of such elevated aldehyde content on several spectral regions of the 1 H spectrum. Finally, a new compound was detected in the OEH samples and is reported for the first time. This compound could possibly be an indicator. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

NMR Analysis of Extra Virgin Olive Oil of the Epirus Region of Greece with Emphasis on Selected Phenolic Compounds

Extra virgin olive oil (EVOO) is recognized for its numerous health benefits, attributed to its rich phenolic components. NMR has emerged as a prevalent technique for precisely identifying these compounds. Among Mediterranean countries, Greece stands as the third-largest producer of olives, with the Epirus region notably advancing in olive cultivation, contributing significantly to the dynamic growth of the region. In this study, an NMR method was employed based on the acquisition of a 1H NMR spectrum along with multiple resonant suppression in order to increase the sensitivity. Using the above method, 198 samples of extra virgin olive oil, primarily sourced from the Epirus region, were analyzed, and both the qualitative and quantitative aspects of the phenolic compounds were obtained. In addition, we examined the effects of various factors such as variety, harvest month, and region origin on the phenolic compounds' concentration. The results revealed an average total phenolic content of 246 mg/kg, closely approaching the EU health claim limit of 250 mg/kg. Approximately 15% of the samples were confidently characterized as high-phenolic olive oil. The highest concentrations were observed in the Thesprotia samples, with several Lianolia varieties exceeding the total phenolic content of 400 mg/kg. Statistical tests demonstrated a significant influence of the olive variety and the month of fruit harvest on phenolic component concentration, followed by the region of origin. A very strong correlation was noted between the total phenolics content and the levels of oleocanthal and oleacein, with a correlation coefficient (r) of 0.924. Upon optimization of all factors affecting olive oil quality, the majority of the EVOOs from the Epirus region have the potential to be characterized as high in phenolic content.

Ruthenium-Cyclopentadienyl-Cycloparaphenylene Complexes: Sizable Multicharged Cations Exhibiting High DNA-Binding Affinity and Remarkable Cytotoxicity

Two novel sizable multicharged cationic complexes, of the formulae [(η6--[12]CPP)[Ru(η5--Cp)]12]Χ12 and [(η6--[11]CPP)[Ru(η5--Cp)]11]Χ11, CPP = cycloparaphenylene, Cp = cyclopentadienyl, X = [PF6]-, (1), (3) and [Cl]-, (2), (4), were synthesized and characterized using NMR techniques, high-resolution mass spectrometry, and elemental analyses. Complexes (1) and (3) were stable in acetone and acetonitrile solutions over 48 h. In contrast, the water-soluble (2) and (4) begin to decompose in aqueous media after 1 h, due to the [Cl]- tendency for nucleophilic attack on ruthenium of the {Ru(η5--Cp)} units. Fluorescence quenching experiments conducted during the stability window of (2) with the d(5'-CGCGAATTCGCG-3')2-EtBr adducts revealed remarkably high values for Ksv = 1.185 × 104 ± 0.025 M-1 and Kb = 3.162 × 105 ± 0.001 M-1. Furthermore, the cytotoxic activity of (2) against A2780, A2780res, and MCF-7 cancer cell lines shows that it is highly cytotoxic with IC50 values in the range of 4.76 ± 1.85 to 16 ± 0.81 μΜ.

Synthesis and Characterization of Ruthenium-Paraphenylene-Cyclopentadienyl Full-Sandwich Complexes: Cytotoxic Activity against A549 Lung Cancer Cell Line and DNA Binding Properties

Novel full-sandwich (η5-Cp)-Ru-paraphenylene complexes with the general formula [(η5-Cp)nRu(η6-L)](PF6)n where n = 1-3 and L = biphenyl, p-terphenyl and p-quaterphenyl, were synthesized and characterized by means of spectroscopic and analytical techniques. The structures of the complexes [(η5-Cp)Ru(η6-biphenyl)](PF6) (1), [(η5-Cp)Ru(η6-terphenyl)](PF6) (3) and [(η5-Cp)2Ru(η6-terphenyl)](PF6)2 (4) was determined by X-ray single crystal methods. The interaction of the complexes [(η5-Cp)Ru(η6-quaterphenyl)]Cl, (6)Cl, and [(η5-Cp)2Ru(η6-quaterphenyl)]Cl2, (7)Cl2, with the DNA duplex d(5'-CGCGAATTCGCG-3')2 was studied using NMR techniques. The results showed that both complexes interacted non-specifically with both the minor and major grooves of the helix. Specifically, (6)Cl exhibited partial binding through intercalation between the T7 and T8 bases of the sequence without disrupting the C-G and A-T hydrogen bonds. Fluorometric determination of the complexes' binding constants revealed a significant influence of the number of connected phenyl rings in the paraphenylene ligand (L) on the binding affinity of their complexes with the d(5'-CGCGAATTCGCG-3')2. The complexes (6)Cl and (7)Cl2 were found to be highly cytotoxic against the A549 lung cancer cell line, with complex (6) being more effective than (7) (IC50 for (6)Cl: 17.45 ± 2.1 μΜ, IC50 for (7)Cl2: 65.83 ± 1.8 μΜ) and with a selectivity index (SI) (SI for (6)Cl: 1.1 and SI for (7)Cl2: 4.8).

Dual-Emissive Rectangular Supramolecular Pt(II)-p-Biphenyl with 4,4'-Bipyridine Derivative Metallacycles: Stepwise Synthesis and Photophysical Properties

Mixed-ligand tetranuclear supramolecular coordination complexes (SCCs) of Pt(II)-p-biphenyl and bridging ligands derivatives of 4,4'-bypiridine (8)-(10), were synthesized and characterized. The SCCs were synthesized stepwise, starting from the Pt-p-biphenyl -Pt core. The crystal structure of complex {[Pt(2,2'-bpy)]4(μ-bph)2(μ-(4,4'-bpy)2}{PF6}4 (2,2'-bpy = 2,2'-bipyridine, bph = p-biphenyl and 4,4'-bpy = 4,4' bipyridine), was determined using single-crystal diffraction methods. The emission profile of the tetranuclear complexes (8)-(10) was influenced by the length of the bridging ligands and was found to depend on solvent polarity. Dual-emission patterns in methanol-water mixtures were observed only in the cases of complexes (9) and (10), attributed to aggregation-induced emission phenomena.

Synthesis, characterization, interactions with the DNA duplex dodecamer d(5'-CGCGAATTCGCG-3')2 and cytotoxicity of binuclear η6-arene-Ru(II) complexes

The novel binuclear η⁶-arene-Ru(II) complexes with the general formula {[(η⁶-cym)Ru(L)]₂(μ-BL)}(PF₆)₄, and their corresponding water soluble {[(η⁶-cym)Ru(L)]₂(μ-BL)}Cl₄, where cym = p-cymene, L = 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen), BL = 4,4'-bipyridine (BL-1), 1,2-bis(4-pyridyl)ethane (BL-2) and 1,3-bis(4-pyridyl)propane (BL-3), were synthesized and characterized. The structure of {[(η⁶-cym)Ru(phen)]₂(μ-BL-1)}(PF₆)₄ was determined by X-ray single crystal methods. The interaction of {[(η⁶-cym)Ru(phen)]₂(μ-BL-i)}Cl₄ (i = 1, 2, 3; (4), (5) and (6) correspondingly) with the DNA duplex d(5'-CGCGAATTCGCG-3')₂ was studied by means of NMR techniques and fluorescence titrations. The results show that complex (4) binds with a K_b = 12.133 × 10³ M^-1 through both intercalation and groove binding, while (5) and (6) are groove binders (K_b = 2.333 × 10³ M^-1 and K_b = 3.336 × 10³ M^-1 correspondingly). Comparison with the mononuclear complex [(η⁶-cym)Ru(phen)(py)]²⁺ reveals that it binds to the d(5'-CGCGAATTCGCG-3')₂ with a K_b value two orders of magnitude lower than (4) (K_b = 0.158 × 10³ M^-1), indicating that for the binuclear complexes both ruthenium moieties participate in the binding. The complexes were found to be cytotoxic against the A2780 and A2780 res. cancer cell line with a selectivity index (SI) in the range of 3.0-5.9.

Synthesis, characterization, interactions with 9-MeG and cytotoxic activity of heterobimetallic RuII-PtII complexes bridged with 2, 2'-bipyrimidine

The complexes [(η⁶-bz)Ru(bpm)Cl]PF₆, (1)PF₆, [(η⁶-bz)ClRu(μ-bpm)PtCl₂]PF₆, (2)PF₆, [(η⁶-cym)ClRu(μ-bpm)PtCl₂]PF₆, (3)PF₆, [(η⁶-cym)ClRu(μ-bpm)PdCl₂]PF₆, (4)PF₆, [Pt(bpm)(cbdca)], (5) and [(η⁶-cym)ClRu(μ-bpm)Pt(cbdca)]PF₆, (6)PF₆, (bz = benzene, bpm = 2,2'-bipyrimidine, cym = p-cymene, cbdcaH₂ = 1,1-cyclobutanedicarboxylic acid),were synthesized and characterized by means of ¹H NMR and high-resolution ESI mass spectrometry. The complexes were transformed to the corresponding chloride salts to become soluble in aqueous media, and to be studied regarding their biological properties. However, while the heterobimetallic complexes (3)Cl and (6)Cl were almost stable, (2)Cl and (4)Cl were decomposed. The interaction of 9-MeG (9-MeG = 9-methylguanine) with (3)Cl and (6)Cl revealed that it coordinates only to the platinum center through N7. Decomposition of the heterobimetallic complexes takes place after the coordination of 9-MeG, mainly forming the complex [Pt(bpm)(9-MeG-N7)Cl]⁺. Notably, the cytotoxic activity of (6)Cl in cancer cells was found to be moderate when compared to cisplatin, but higher in comparison with its corresponding monomers.

Stepwise synthesis, characterization, DNA binding properties and cytotoxicity of diruthenium oligopyridine compounds conjugated with peptides

Although the interactions of oligopyridine ruthenium complexes with DNA have been widely studied, the biological activity of similar diruthenium oligopyridine complexes conjugated with peptides has not been investigated. Herein, we report the stepwise synthesis and characterization of diruthenium complexes with the general formula [(L^a)Ru(tppz)Ru(L^b)]ⁿ⁺ (tppz = 2,3,5,6-tetra(2-pyridyl)pyrazine, L^a = 2,2':6',2''-terpyridine or 4-phenyl-2,2':6',2''-terpyridine and L^b = 2,2':6',2''-terpyridine-4'-CO(Gly¹-Gly²-Gly³-LysCONH₂) (5), (6), n = 5; 2,2':6',2''-terpyridine-4'-CO(Gly¹-Gly²-Lys¹-Lys²CONH₂) (7), (8), n = 6; 2,2':6',2''-terpyridine-4'-CO(Ahx-Lys¹Lys²CONH₂) (9), (10), n = 5, Ahx = 6-aminohexanoic acid). The compounds [(trpy)Ru(tppz)Ru(trpy-CO₂H)](PF₆)₄, (2)(PF₆)₄, [(ptrpy)Ru(tppz)Ru(trpy-CO₂H)](PF₆)₄, (3)(PF₆)₄ and [(ptrpy)Ru(tppz)Ru(trpy)](PF₆)₄, (4)(PF₆)₄ were also characterized by single crystal X-ray methods. Moreover, the interactions of the chloride salts (5), (6) and (4) with the self-complementary dodecanucleotide duplex d(5'-CGCGAATTCGCG-3')₂ were studied by NMR spectroscopic techniques. The results show that complex (4) binds in the central part of the oligonucleotide, from the minor groove through the ligand ptrpy, while the ligand trpy, which was located on the other side of the diruthenium core, does not contribute to the binding. Complex (5) binds similarly, through the ligand ptrpy. However, the induced upfield shifts of the ptrpy proton signals are significantly lower than the corresponding ones in the case of (4), indicating much lower binding affinity. This is clear evidence that the tethered peptide Gly¹-Gly²-Gly³-Lys¹CONH₂ hinders the complex binding, even though it contains groups that are able to assist it (e.g., the positively charged amino group of lysine, the peptidic backbone, the terminal amide). Complex (6) shows a non-specific binding, interacting through electrostatic forces. The chloride salts of (4), (5) and (6) had insignificant effects on the cell cycle distribution and marginal cytotoxicity (IC₅₀ > 750 μM) against human lung cancer cell lines H1299 and H1437, indicating that their binding to the oligonucleotide is not a sufficient condition for their cytotoxicity.

Synthesis, reactivity and characterization of Pt(ii) complexes with N,N′ chelating ligands; structure and dimethylsulfoxide reactivity relationship

Chelated N-heterocycles can be replaced from the coordination sphere of square planar Pt(ii) complexes by DMSO.

Synthesis and characterization of ruthenium(II)-oligopyridine-peptide conjugates. Interactions of the diasteromeres Δ- and Λ-[Ru(bpy)2(4-COY-4'-Mebpy)]Cl2 (Y=Gly-Lys(1)-Lys(2)CONH2, Lys(1)-Gly-Lys(2)CONH2, Lys(1)-Lys(2)-GlyCONH2) with the oligonucleotide d(5'-CGCGAATTCGCG-3')2

Diastereomeric complexes of the general formulae Λ- and Δ-[Ru(bpy)2(4-COY-4'-Mebpy)]Cl2 where bpy=2,2'-bipyridine and Y=Gly-Lys(1)-Lys(2)CONH2, Lys(1)-Gly-Lys(2)CONH2, Lys(1)-Lys(2)-GlyCONH2, were synthesized and characterized. The ability of these compounds to bind to the oligonucleotide duplex d(5'-CGCGAATTCGCG-3') was studied with NMR techniques. Complex Λ-2, Λ-[Ru(bpy)2(4-COLys(1)-Gly-Lys(2)CONH2),4'-Mebpy)]Cl2 (Mebpy=methyl-2,2'-bipyridine), interacts non-specifically causing changes for both complex and oligonucleotide (1)H NMR signals. Both Λ-1, Λ-[Ru(bpy)2(4-COGly-Lys(1)-Lys(2)CONH2),4'-Mebpy)]Cl2 and Λ-3, Λ-[Ru(bpy)2(4-COLys(1)-Lys(2)-GlyCONH2),4'-Mebpy)]Cl2, were bound to the oligonucleotide through both lysine aliphatic chains, indicating that the side chains of the sequential lysines create a kind of "clamp" to connect the complex with the oligonucleotide. Complex Δ-1, Δ-[Ru(bpy)2(4-COGly-Lys(1)-Lys(2)CONH2),4'-Mebpy)]Cl2, interacts with the oligonucleotide duplex with both lysine side chains in a manner similar to Λ-1. Δ-2, Δ-[Ru(bpy)2(4-COLys(1)-Gly-Lys(2)CONH2),4'-Mebpy)]Cl2, interacts with the oligonucleotide with the bipyridine ligands. In addition, the formation of a hydrogen bond between the Gly-NH and the carbonyl groups of the oligonucleotide bases was detected. A completely different binding mode was observed for Δ-3 Δ-[Ru(bpy)2(4-COLys(1)-Lys(2)-GlyCONH2),4'-Mebpy)]Cl2, which at a ratio of 1:1 ([Ru]/[nucleotide]) opens the oligonucleotide strands. In addition, participation of all three peptidic NH of Δ-3 in hydrogen bonds was observed.

Oligopyridine-ruthenium(II)-amino acid conjugates: synthesis, characterization, DNA binding properties and interactions with the oligonucleotide duplex d(5'-CGCGCG-3')2

Diastereomeric oligopyridine-ruthenium(II)-amino acid conjugated complexes of the general formulas Lambda- and Delta-[Ru(bpy)(2)(4,4'(CO(2)Y)(2)-bpy)](2+), where Y = L-AlaCONH(2), L-LysCONH(2), L-HisCONH(2), L-TyrCONH(2)), were synthesized and characterized. Their binding properties with ct-DNA and the oligonucleotide duplex d(5'CGCGCG-3')(2), by means of circular dichroism (CD), NMR spectroscopy and DNA thermal denaturation (T(m)) curves were studied. CD and T(m) data indicate that all diastereomeric complexes bind to the DNA major groove, Delta-diastereomers in a similar manner, while Lambda-diastereomers in dependence of the nature of the amino acid. NMR studies of d(5'CGCGCG-3')(2), and the complexes Delta-1, Delta-2, Lambda-1 and Lambda-2 indicate that Delta-1 and Delta-2 were bound having the ancillary bpy ligands towards the DNA groove, while the corresponding Lambda-1 and Lambda-2 were orientated in a similar way, facing the ligand 4,4'(CO(2)Y)(2)bpy towards the DNA major groove. Photoinduced DNA cleavage was observed in all cases studied, which take place through singlet oxygen production. Delta-4 and Lambda-4 show the lower photoinduced cleavage yield, probably because the singlet oxygen ((1)O(2)) oxidizes not only the DNA phosporodiesteric bonds but the tyrosine's phenolic OH bond as well.

Synthesis, characterization and DNA binding properties of oligopyridine-ruthenium(II)-amino acid conjugates

The DNA-binding properties of a number of ruthenium oligopyridine complexes with conjugated amino acids having the general formulae [Ru(terpy)(4-COY-4'-Mebpy)(X)](n)(+), X=NO (n=3), X=Cl (n=1) and NO(2) (n=1) and Y=AlaCONH(2) and TrpCONH(2) are reported. The new complexes were spectroscopically characterized and their DNA-binding properties were studied by means of circular dichroism (CD), (23)Na and (31)P NMR spectroscopy. The results show that the chlorido complexes interact by coordination to the DNA bases with the conjugated amino acid able to provide an additional interaction with the DNA helix. In addition, electrostatic interactions between all studied complexes and the DNA polyanion were observed. The nitro complexes were found to be insignificant, affecting only the (31)P NMR signal, probably due to changes in the hydration sphere of the DNA close to the phosphates.

Synthesis, Characterization, and DNA-Binding Studies of Nitro(oligopyridine)ruthenium(II) Complexes

The complexes of general formulas [RuII(terpy)(4-CO2H-4'-Mebpy)(X)]n+ (X = NO (n = 3) and NO2 (n = 1); 1, 2) and [RuII(terpy)(4-COGHK-4'-Mebpy)(X)] (X = NO (n = 3) and NO2 (n = 1); 3, 4) were synthesized and characterized. The complex [RuII(terpy)(4-CO2-4'-Mebpy)(NO2)]_7.5H2O has also been characterized by X-ray crystallographic studies. It crystallizes in the triclinic system: a = 9.4982(1) A, b = 13.1330(1) A, c = 14.2498(2) A; alpha = 110.5870(6) x bc, beta = 98.4048(5) x bc, gamma = 106.4353(5), P1, Z = 2. The crystal structure reveals an extended hydrogen-bonding network. Two water molecules form strong hydrogen bonds with the nitro and the carboxylic oxygen atoms of two separate units of the complex, resulting in a dimeric unit. The dimers are bridged by a (H2O)15 cluster, consisting of two cyclo-(H2O)6 species, while an exo-H2O(8) connects them. Two more exo-H2O molecules are joined together and connect the cyclo-(H2O)6 units with the H2O(1) of the dimeric unit. It was found that complexes 1 and 3 can be transformed into their nitro derivatives in aqueous media at neutral pH. Photorelease of NO in dry MeCN solutions was observed for complexes 1 and 3. Also, complex 2 partially releases (NO2)- in MeCN upon visible light irradiation. Complex 2 interacts with short fragments (70-300 bp) of calf thymus DNA shortening slightly the apparent polynucleotide length, while the conjugation of the peptide GHK to it (2) affects its DNA-binding mode. The peptide moiety of complex 4 was found to interact with the DNA helix in a synergistic way with the whole complex. Preliminary results of photocleavage of DNA by complex 2 are also reported.

NMR analysis of duplex d(CGCGATCGCG)2 modified by Λ- and Δ-[Ru(bpy)2(m-GHK)]Cl2 and DNA photocleavage study

The interaction of the diastereomeric complexes Lambda-[Ru(bpy)2(m-GHK)]Cl2 and Delta-[Ru(bpy)2(m-GHK)]Cl2 (bpy is 2,2'-bipyridine, GHK is glycine-L-histidine-L-lysine) with the deoxynucleotide duplex d(5'-CGCGATCGCG)2 was studied by means of 1H NMR spectroscopy. At a Delta-isomer to DNA ratio of 1:1, significant shifts for the metal complex are observed, whereas there is negligible effect on the oligonucleotide protons and only one intermolecular nuclear Overhauser effect (NOE) is present at the 2D nuclear Overhauser enhancement spectroscopy spectrum. The 1Eta NMR spectrum at ratio 2:1 is characterized by a slight shift for the Delta-isomer's bpy aromatic protons as well as significant shifts for the decanucleotide G4 H1' and Eta2'', A5 H2, G10 H1', T6 NH and G2 NH protons. Furthermore, at ratio 2:1, 11 intermolecular NOEs are observed. The majority of the NOEs involve the sugar Eta2' and Eta2'' protons sited in the major groove of the decanucleotide. Increasing the Delta-isomer to d(CGCGATCGCG)2 ratio to 5:1 results in noteworthy spectral changes. The Delta-isomer's proton shifts are reduced, whereas significant shifts are observed for the decanucleotide protons, especially the sugar protons, as well as for the exchangeable protons. Interaction is characterized by the presence of only one intermolecular NOE. Furthermore, there is significant broadening of the imino proton signals as the ratio of the Delta-isomer to DNuAlpha increases, which is attributed to the opening of the two strands of the duplex. The Lambda-isomer, on the other hand, approaches the minor groove of the oligonucleotide and interacts only weakly, possibly by electrostatic interactions. Photocleavage studies were also conducted with the plasmid pUC19 and a 158-bp restriction fragment, showing that both diastereomers cleave DNA with similar efficiency, attacking mainly the guanines of the sequence probably by generating active oxygen species.

Interaction of Lambda- and Delta-[Ru(bpy)2(pbmz)](PF6)2 with the oligonucleotide duplex d(CGCGAATTCGCG)2

The interaction of the enantiomeric complexes Lambda- and Delta-[Ru(bpy)(2)(pbmz)](PF(6))(2) (bpy=2,2'-bipyridine, pbmz=2-(2'-pyridyl)benzimidazole) with the DNA duplex d(CGCGAATTCGCG)(2) was investigated by means of 2D NMR techniques. The synthesis of the enantiomers was based on the optically pure complexes Lambda- and Delta-[Ru(bpy)(2)(py)(2)](2+) and were characterized by CD and NMR spectroscopy. NMR data indicate that both enantiomers bind weakly to the oligonucleotide, approaching from the minor groove at the centre of the helix. The perturbation of the B-DNA conformation is minor with an apparent absence of enantioselectivity. Molecular modelling calculations in conjunction with the NOE data support the suggestion that more than one binding modes are present. The imidazole amine group of the pbmz ligand is probably hydrogen bonded to the DNA phosphodiesteric backbone at the AATT step, and this may provide an explanation for the diminished enantioselectivity observed.

Synthesis and characterization of the diastereomers Lambda- and Delta-[Ru(bpy)2(m-bpy-L-Arg-Gly-L-Asn-L-Ala-L-His-L-Glu-L-Arg)]Cl2 1H NMR studies on their interactions with the deoxynucleotide duplex d[(5'-GCGCTTAAGCGC-3')2] and d[(5'-CGCGATCGCG-3')2]

The diastereomeric complexes Lambda- and Delta-[Ru(bpy)(2)(m-bpy-7p)]Cl(2), (bpy=2,2'-bipyridine, m-bpy-7p=4-methyl-4'-Arg-Gly-Asn-Ala-His-Glu-Arg-CONH(2)-2,2'-bipyridine) were synthesized and characterized and their binding properties to the deoxynucleotide duplexes d(5'-CGCGATCGCG-3')(2) and d(5'-GCGCTTAAGCGC-3')(2) were studied by means of (1)H NMR spectroscopy. 7p is part of the recognition loop of the restriction endonuclease MunI, a type II restriction enzyme from Mycoplasma unidentified which recognizes the palindromic hexanucleotide sequence C/AATTG and cleaves it as indicated by the slash. The Delta-isomer binds to the terminal CG/GC major groove of d(CGCGATCGCG)(2) decanucleotide, whereas the Lambda-isomer approaches the GCT/CGA sequence. On the other hand, weak binding of the Delta-isomer to the end of d(GCGCTTAAGCGC)(2) into two different orientations is observed. In the case of the Lambda-isomer, the bpy ligand(s) are located into the major groove of the central TT/AA sequence. The role of appended peptide sequences in sequence selectivity binding to DNA is being addressed.

Synthesis, characterization, in vitro antitumor activity, DNA-binding properties and electronic structure (DFT) of the new complex cis-(Cl,Cl)[RuIICl2(NO+)(terpy)]Cl

The complex cis-(Cl,Cl)-[RuCl2(terpy)(NO)]Cl (1) has been synthesized by the reaction of [RuCl3(H2O)2(NO)] with terpyridine (terpy) and characterized by various spectroscopic, analytical techniques and using electronic structure calculation (DFT) methods. The cytotoxic activity and the DNA-binding properties of have also been studied using biochemical techniques. The results establish unequivocally that corresponds to a so-called [RuNO]6 species, which readily releases the nitrosyl ligand upon irradiation with a mercury lamp in acetonitrile solution. DFT calculations provided a satisfactory description of structural, bonding, electronic and related properties of the new compound and throw light on the mechanism of the photo-induced NO release. Screening on A2780 (human ovarian carcinoma) cell lines showed significant cytotoxicity with an IC50 value of 0.49 microM. 31P and 23Na NMR spectroscopy along with electrophoretic mobility studies illustrated that complex primarily binds by coordination to DNA without any pi-interaction between the planar terpy ligand and the DNA bases, while weak electrostatic interactions could not be excluded. Studies on the inhibition of the restriction enzymes DraI and SmaI revealed that prefers the guanine and cytosine bases of DNA.

Solid-phase synthesis, characterization and DNA binding properties of the first chloro(polypyridyl)ruthenium conjugated peptide complex

A general method for the synthesis of chloro(polypyridyl)ruthenium conjugated peptide complexes via a solid-phase strategy is described. The method is applied to synthesize two positional isomers of the complex [Ru(terpy)(4-CO2H-4'-Mebpy-Gly-L-His-L-LysCONH2)Cl](PF6). Even though the separation of the isomers was only partially achieved chromatographically, the isomers were unambiguously assigned by NMR spectroscopy. The interactions of the complex [Ru(terpy)(4-CO2H-4'-Mebpy-Gly-L-His-L-LysCONH2)Cl](PF6) with CT-DNA and plasmid DNA, have been studied with various spectroscopic techniques, showing that (i) the complexes coordinatively bind to DNA preferring the bases guanine and cytosine over the bases thymine and adenine after hydrolysis of the coordinated chloride, (ii) electrostatic interactions between the complex cation and the polyanionic DNA chain assist this binding (iii) only in the case of one isomer the peptide does interact further with DNA as evidenced from 31P NMR spectroscopy, (iv) DNA unwinding occurs in all cases with high binding ratio (Ru/base) values (r > 0.3).

Enantioselective binding of lambda- and delta-[Ru(bpy)(2)(HPIP)]Cl2 (HPIP=2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthroline) to the hexanucleotide [d(5'-GTCGAC-3')2]

Multidimensional NMR techniques (1D (1)HNMR, 2D DQF (1)H(1)H COSY and 2D (1)H(1)H NOESY), electrospray ionization mass spectrometry (ESI-MS) and electronic spectroscopy, were performed to study the interactions of the enantiomers lambda- and delta-[Ru(bpy)(2)(HPIP)]Cl(2), (HPIP=2-(2-hydroxyphenyl)imidazo[4,5-f][1,10]phenanthro-line) with the self complementary hexanucleotide duplex d(5'-GTCGAC-3')(2). The results show that the delta-[Ru(bpy)(2)(HPIP)]Cl(2) binds tightly to the oligonucleotide, by intercalation of the ligand HPIP, between the A5 and C6 base sequence of the same strand, probably through the minor groove. Lambda-enantiomer binds weakly, suggesting groove interactions with the hexanucleotide duplex. ESI-MS spectrometry and UV-vis spectroscopy also confirmed these observations.

Sequence-selective metal ion binding to DNA oligomers

Sequence-selective interactions between DNA oligonucleotides and Pt(II) and Pd(II) complexes have been studied by 1D and 2D NMR spectroscopy. Titration of DNA oligomers with diamagnetic metal ion complexes induces chemical shifts of proton resonances close to the site of interaction. Conformational changes in the helical structure were monitored by measuring cross-peak intensities in 2D NOESY maps. Two duplex deoxynucleotides were studied, [d(CGCGCG)]2 and [d(CGCGAATTCGCG)]2, respectively. The hexamer was titrated in the duplex form with cis-[Pt(NH3)2Cl2]2+ (cis-DDP or cisplatin). The dodecamer was titrated with NO(3-)-salts of Pd(aq)2+, [Pd(en)(H2O)2]2+ and [Pd(dien)(H2O)]+, respectively. The reaction between cis-DDP and the hexamer at conditions where the duplex form is retained proceeded exceedingly slowly. In the initial phase of the titration the NOESY map indicates conformational changes induced by noncovalent adduct formation between the intact hexamer and cis-DDP. The more reactive Pd compounds show a tendency towards sequence-selective binding to the duplex dodecamer. The 'naked' Pd ion is very reactive and exhibits selectivity towards the thymine T8 imino proton and N7 on G4. At a Pd(II)/dodecamer ratio of 4:1 the metal ions induce helix-->coil transition. The mono- and bifunctional Pd complexes with 'bulky' ligands attack the dodecamer at the terminal GC base pairs, leaving the central Watson-Crick base pairs intact.

Interaction of cis-Pt(ino)2Cl2 with amino acids

The reactions of cis-Pt(ino)2Cl2 with the amino acids Gly, L-Ala, L-Val, L-Ileu, L-Phe and L-Pro were studied in methanolic solutions. The (1:1) adducts of the formulas cis-[Pt(ino)2(am-ac)]Cl were isolated from these reactions in the solid state, which in turn produce the cis-[Pt(ino)2(am-acH)Cl]Cl complexes, by treating the former with equivalent amounts of HCl, in aqueous solutions. The complexes were characterized with elemental analysis, conductivity measurements, IR, 1H NMR, and 13C NMR spectra. The results show that the purine ring of inosine interacts with the aliphatic side chain of the amino acids. The platination increases the percentage of the C3'-endo-anti conformation of the sugar part of inosine.