Almost all antibiotics target either bacterial function or biofilms but do not consider the damage due to host responses, thus, even if the bacteria are eliminated, the tissue damage cannot be prevented. The mucoid phenotype and oxidative stress severely limit the efficacy of current therapeutics for chronic respiratory infections (CRI) of Pseudomonas aeruginosa in cystic fibrosis (CF) patients. In the present study, we examined the activity of a novel set of VitaminK3 derivatives on biofilms of the mucoid variants of P.aeruginosa. Acyl-homoserine lactones (AHLs) an important signaling molecules in the quorum sensing gene regulatory processes found in numerous gram-negative species of bacteria were evaluated. Further, the radical scavenging ability and antibiofilm activities were studied. The compounds were also screened for cytotoxic activity by the MTT assay on HeLa cell lines. This work highlights the aggravation of the CF lung caused due to biofilm formation, and exacerbation occurring due to oxidative stress, which is a host response. This study thus presents VitaminK3 derivatives as antimicrobial compounds which also prevent oxidative stress and thus serve a dual function. Consequently, further development and use of these compounds is likely to complement current CF therapeutics.

Menadione (Vitamin K3) comprises of 1,4-naphthoquinone (NQ) moiety that can form redox isomers such as napthosemiquinone (NSQ) and catechol by accepting one or two electrons, respectively. The quinone redox cycling ability leads to the generation of "reactive oxygen species" (ROS) as well as arylation reactions, which are of biological relevance. This ability can be modulated with the help of suitable derivatization. A pharmacophore can be appended at suitable position of Vitamin K3 to have a synergistic or additive effect. In the present review, an attempt has been made to accrue such derivatives modified at 1 or 2 position and evaluated for their cytotoxicity activity on different series of human cancer cell lines such as HeLa, HL-60 and MCF- 7 etc. Production of reactive oxygen species (ROS) and mitochondrial dysfunction caused by Vitamin K3 derivatives leads to apoptosis and tumor inhibition. Recently, the CR-108 compound has shown to exhibit oxidative path together with non-oxidative phosphorylation of p38 MAP kinase in human breast cancer cells. Thus the chemical-biological interactions have been discussed which can be further extrapolated for the development of a potent anticancer drug.

1,1'-Methide-bi-vitamin K-3 (B) has been isolated as a dinaphthoquinone methide radical (DNQM) by the transformation of 1-imino(acetylhydrazino)-vitamin K-3 (A). The transformation follows a biomimetic activation pathway mediated via Cu(II) ion catalyzed oxidative coupling. Single crystal X-ray and electron spin resonance (ESR) experiments combined with density functional calculations elucidate the "resonance structure" of the DNQM radical (B). Fluorescence investigations reveal that DNQM facilitates interaction with the cysteine residue. As compared to the parent substrate, B shows a depletion in the level of GSH, triggering apoptosis in HeLa cells.

Compound 1 [1-imino (acetyl hydrazino)–Vitamin K3], displays valence tautomerically related electronic isomers as Form I and Form II. Form I exhibits 2D packing fragment with 1D ribbon chains of N–H⋯O hydrogen bonds and shows EPR silent features. While Form II is EPR active and exhibits biradical nature with double quantum transitions at g=2.0040. 1H NMR of compound 2, [1-imino (hydrazino carboxylate)–Vitamin K3] and Form II exhibit π delocalization via resonance assisted H-bonding [RAHB] effect compared to Form I. Molecular interactions in Form I and II are visualized by DSC. The electronic structures of compounds 1 and 2 have been correlated to their API values by measuring anticancer activities, mitochondrial potentials and DNA shearing patterns. Form II and compound 2 indicate mitochondria mediated apoptosis (∼75% cell death) while Form I causes 35% cell death.

Crystal engineering based on halogen bonding together with host–guest interactions of water molecules via H-bonding, stabilizing supramolecular architecture in chloro 1, bromo 2 and iodo 3oximes of lawsone, is discussed. 1 and 2 crystallize in orthorhombic, non-centrosymmetric space group Pna21 while 3 crystallizes in monoclinic P21/n space group. Non-covalent competitive interactions of asymmetric solvation and halogen bonding can have a large influence on the spin distribution in 1, 2 and 3 derivatives of spin carrier lawsone live polymer as revealed by single crystal X-ray and EPR studies. The significant C3–Cl/Br⋯O, C3–Cl/Br⋯H, O–H⋯OC, C–H⋯π and π⋯π interactions have been identified in the molecular assemblies leading to net magnetostructures of halo-oximes. Dimer-of-dimer-type tetrameric radical assembly of 3 and interacting bi- and monoradical chain on 21 axis in 1 and 2 have been identified. The proton-coupled electron transfers possibly govern the antioxidant nature in halooximes of spin carrier lawsone in terms of oxygen reduction to water molecules. Such activity is found to be directly proportional to the spin (radical) concentrations in 1 to 3 and increases in order 1 < 2 < 3 according to halogen bonding effect. The antioxidant chemical DPPH assays for scavenging of such free radicals result in similar trend of increasing order like 1 < 2 < 3, but the chemical in vitro as well as ex vivoSOD antioxidant activities and biological anticancer activity on MCF-7, Hela and HL-60 cell lines show the increasing order 3 < 2 < 1 according to H-bonding effect. This probably could be attributed to the conversion of superoxide radical ions into H2O2, which leads to greater oxidative stress leading to apoptosis.

Electronic structure and spectroscopic properties of the novel diiron active site of oxidized mammalian purple acid phosphatase analogues, Fe-6: [Fe 2 (μ-O) (μ-OAc) (4HNSQ ox ) ∸ (ONSQ ox ) 2∸ (H 2 O) 4 ] and Fe-7: [Fe 2 (μ-O) (μ-OAc)(ONSQ ox ) 2∸ (OAc)(H 2 O) 4 ] are described. Magnetic susceptibility SQUID data of Fe-6 are best fitted to Heisenberg's isotropic spin pair (S = 5/2, 3/2) model using magnetic parameters g = 2 and J = - 36.8 cm -1 with R factor = 6.4 x 10 -4 . The antiferromagnetic exchange establishes Fe(III)-O-Fe(III) dimeric core with Fe(III) site having two radical ligations in the naphthosemiquinone oxime form of lawsone oxime. In the model compound Fe-7 of oxidized purple acid phosphatase, bridged and terminal acetate functions are identified according to their different energies of activations, i.e, ~34 and 58 kJ mol - respectively. Also, the reduced naphthoquinone oxime form of ligand is characterized by its energy of activation (~15 kJ mol -1 ) from pyrolytic reaction. Mossbauer parameters, δ = 0.4 mm s -1 and ΔE Q = 0.8 mm s -1 , are characteristics of oxidized Fe(III) in high spin octahedral site. Only Fe-6 shows analogous physiological DNA cleavage activity on pUC19 plasmid and acts as a good model of oxidized purple acid phosphatase enzyme.

Crystal structure, 1H NMR and cyclic voltammetric investigations of 2-(o-hydroxy-anilino)-1,4-napthoquinone (HAN), resulting from coupling of aminophenol with 2-hydroxy-1,4-napthoquinone, have been carried out. X-ray structure reveals that the HAN ligand crystallizes in orthorhombic space group Pca21 with Z=4, forming a chain via inter-molecular O2⋯H1AO1 and C15H15⋯O3 interactions. Both 1H NMR and cyclic voltammetry experiments suggest the titled ligand is associated and exists as dimer in d6-DMSO while the monomer has been predicted in CDCl3 solution. Density functional calculations can be utilized to gauge the strength of hydrogen-bonded interactions from the 1H chemical shifts in the NMR spectra. Self-consistent reaction field (SCRF) calculations further support the inferences drawn from cyclic voltammetry experiments.

The molecular mass of acid phosphatase (APase) from Solanum tuberosum is estimated as 111 kDa using denaturing SDS-PAGE. The prime catalytic di-iron Fe 2+ /Fe 3+ site (1.62 ± 0.2 mole) together with the co-catalytic sites of manganese, zinc and trace copper (0.397 ± 0.135 mole) in the enzyme have been determined by the GF-AAS technique. The quantitation of the biphasic release of iron species from the enzyme has been carried out spectrophotometrically. The reduction (~70-72%) in biological activity of APase after removal of the divalent metal constellation of co-catalytic site made up of Fe 2+ , Mn 2+ , Cu 2+ and Zn 2+ is established after duplicate treatment of enzyme from a Chelex-100 column. The significance of redox active Fe 2+ /Fe 3+ metal cofactors at the active site of the enzyme correlates well with the affinity of substrate binding towards the di-iron site in terms of kinetic parameters. A physiological defense activity of APase is established in terms of its quantitative pUC-19 plasmid DNA cleavage activity.

Three polymorphs of 3-iodolawsone (I–III) have been isolated and characterized by single crystal X-ray diffraction, electron paramagnetic resonance (EPR) spectroscopy and differential scanning calorimetry (DSC) techniques. Polymorphs I and II were crystallized from methanol in two different valence tautomeric forms: hydroxynaphthoquinone (HNQ) and hydroxynaphthosemiquinone (HNSQ) as needles and thick plates, respectively. Polymorph III was crystallized from ethanol in HNQ form, as thin plates. Chiral crystals of I belongs to the orthorhombic P212121 space group; II and III belong to the monoclinic non-centrosymmetric space group Cc. The molecules are packed via OH⋯O bonding and π⋯π stacking interactions. The study reveals that relatively stronger intermolecular H-bonding (2.02Å) and most favoured π⋯π stacking (∼3.49Å) interactions lead II to HNSQ radicals, presence of which was confirmed by EPR (g=2.0052) spectroscopy. Interestingly, these materials exhibit crystal-to-crystal magnetic phase transition from polymorph I (diamagnetic) to polymorph II (paramagnetic structure) at 171.1°C as identified by DSC and X-ray crystallographic studies.

Temperature-induced packing polymorphism is observed for vitamin K3 (menadione, 3-methyl-1,4-naphthoquinone, 1). Form 1a crystallizes at 300K and 1b at 277K both in the same space group P21/c. Form 1b contains one molecule per asymmetric unit, performing anisotropy in g-factor viz. gz=2.0082, gy=2.0055 and gx=2.0025, whereas form 1a contains two molecules in its asymmetric unit. Vitamin K3 family members 2, [2-hydroxy vitamin K3] and 3, [2-hydroxy-1-oximino vitamin K3] also perform intrinsic neutral active naphthosemiquinone valence tautomers even in dark having spin concentrations due to hydrogen bonding and aromatic stacking interactions which are compared to vitamin K3. The significant lateral C–H⋯O and O–H⋯π bifurcated or π–π∗ interactions are discussed for molecular associations and radical formations. X-ray structure of 3 revealed π–π∗ stack dimers as radicals signatured in EPR as triplet with five hyperfine splits [Ā(14N)=11.9G]. The centrosymmetric biradicals in 3 show diamagnetism at high temperature but below 10K it shows paramagnetism with μeff as 0.19 B.M. Vitamin K3 and its family members inhibit biological activities of acid phosphatase (APase), which are proportional to their spin concentrations. This may relate to their probable anti-oncogenic candidature in future.

Purple acid phosphatase, (PAP), is known to contain dinuclear Fe2  + 2, + 3 site with characteristic Fe + 3 ← Tyr ligand to metal charge transfer in coordination. Phthiocoloxime (3-methyl-2-hydroxy-1,4-naphthoquinone-1-oxime) ligand L, mimics (His/Tyr) ligation with controlled and unique charge transfers resulting in valence tautomeric coordination with mixed valent diiron site in model compound Fe-1: [μ-OH-Fe2  + 2, + 3 (o-NQCH3ox) (o-NSQCH3ox)2 (CAT) H2O]. Fe-2: [Fe + 3(o-NQCH3ox) (p-NQCH3ox)2]2 a molecularly associated dimer of phthiocoloxime synthesized for comparison of charge transfer. 57Fe Mössbauer studies was used to quantitize unusual valences due to ligand in dimeric Fe-1 and Fe-2 complexes which are supported by EPR and SQUID studies. 57Fe Mössbauer spectra for Fe-1 at 300 K indicates the presence of two quadrupole split asymmetric doublets due to the differences in local coordination geometries of [Fe + 3]A and [Fe + 2]B sites. The hyperfine interaction parameters are δ A = 0.152, (ΔE Q)A = 0.598 mm/s with overlapping doublet at δ B = 0.410 and (ΔE Q)B = 0.468 mm/s. Due to molecular association tendency of ligand, dimer Fe-2 possesses 100% Fe + 3(h.s.) hexacoordinated configuration with isomer shift δ = 0.408 mm/s. Slightly distorted octahedral symmetry created by NQCH3ox ligand surrounding Fe + 3(h.s.) state generates small field gradient indicated by quadrupole split ΔE Q = 0.213 mm/s. Decrease of isomer shifts together with variation of quadrupole splits with temperature in Fe-1 dimer compared to Fe-2 is result of charge transfers in [Fe2  + 2, + 3 SQ] complexes. EPR spectrum of Fe-1 shows two strong signals at g 1 = 4.17 and g 2 = 2.01 indicative of S = 3/2 spin state with an intermediate spin of Fe + 3(h.s.) configuration. SQUID data of \(\chi _m^{{\rm corr}} \mbox{.T}\) were best fitted by using HDVV spin pair model S = 2, 3/2 resulting in antiferromagnetic exchange (J = −13.5 cm − 1 with an agreement factor of R = 1.89 × 10 − 5). The lower J value of antiferromagnetic exchange leads to Fe+3μ-(OH) Fe + 2 bridging in Fe-1 dimer instead of μ-oxo bridge. The intermolecular association through H-bonds may lead to weakly coupled antiferromagnetic interaction between two Fe-2 molecules having Fe + 3(h.s.) centers. Using S = 5/2, 5/2 spin pair model we obtained best-fitted parameters such as J = −12.4 cm − 1, g = 2.3 with R = 3.58 × 10 − 5. Synthetic strategy results in non-equivalent iron sites in Fe-1 dimer analogues to PAP enzyme hence its reconstitution results in pUC-19 DNA cleavage activity, as physiological functionality of APase. It is compared with nuclease activity of Fe-2 RAPase.

Thermal, magnetic and electrochemical properties of the complex 1, [Cu-2 (mu-CO3) (ONQ)(2) (4HNQ)(2)] are discussed [where ONQ=2-oxido-1, 4-napthoquinone and 4HNQ=4-hydroxy-1, 2-naphthoquinone]. The coordination of the ligand is in tautomeric forms viz. ONQ and 4HNQ in 1. The carbonate anion acts as a bridge between two Cu (II) centers showing bidentate (mu-eta(1) -eta(1) -CO32-) coordination mode with distorted square based pyramidal geometry for each Cu(II) ion. Temperature-dependent zero field splitting (zfs) interactions (D and E) are resolved from X- (300K and 77 K) and Q-band (300K) EPR spectra. At 300K, E>D and at 77K, D>E. It reveals temperature dependent modes of coordination viz. syn-anti and anti-anti of ancillary ligand in 1. Variable temperature magnetic susceptibility (SQUID) measurements show a weak antiferromagnetic coupling between the two Cu (II) centers. The susceptibility data was best fitted with HDVV model and the coupling constant found to be J=-4.8 cm(-1) with agreement factor R=2.41*10(- 8). Metal based redox couple assigned at E-1/2 =+0.18 V with Delta E=0.125 V corresponds to two electrons transfer in the Cu (II)double left right arrow Cu (0) redox couple.

Investigation on solvent-induced polymorphism in X-ray structures of 2-hydroxy-1,4-naphthoquinone (Lawsone) 1, is carried out. In protic methanol, 1 crystallizes in monoclinic space group P21/c (1a) comprising of 2D hydrogen bonded network via cyclic dimers. In aprotic solvent such as acetone on the other hand, 1 exhibits orthorhombic space group Pna 21 (1b) and emerges with 1D catemeric chain. Solvent-induced topological isomerism of cyclic dimers and helical catemeric chains arising from (i) bifurcated intra- and inter molecular hydrogen bondings viz. OH⋯OC interactions between C(2) hydroxyl and C(1), C(4) carbonyls, (ii) CH⋯O interactions viz. C(3)H⋯O(1)C(1) have been discussed. A signal for radical in 1 at g=2.0058 is signatured by EPR spectrum and it's oxime derivative viz. 2-hydroxy-4-naphthoquinone-1-oxime 2, in solid state shows biradical and monoradical formation with aggregation of dimer and monomer due to non-covalent hydrogen bonds. Zero field split parameters for 2 are estimated to be D=215G, Ex=13G, Ey=47G at 298K. A half field signal at 77K indicates triplet ground state. Frozen glass EPR of 2 resolves as regioregular dimeric–monomeric species showing hyperfine interactions with 1-oximino nitrogen in dimer A¯(14N)=15.5G].

To reveal reaction mechanism of PS-II, the reaction products of photolysis may be compared with their thermolytic products. According to required molecular assemblies in manganese clusters at WOC of PS-II, we have strategically synthesized dimers (M-1, M-2), trimers (M-3A, M-3B) and tetramer (M-4) using spin carrier imino-phenol functionalized ligands viz. Lawsone Oxime (L-1) and Phthiocol Oxime (L-2) of naturally occurring quinones .These are characterized by elemental analyses, thermogravimetric analyses, differential thermal analyses, powder X-ray diffraction and infrared spectroscopy. Stabilization energies for molecular associations of ligands in various redox and stereoisomeric forms via hydrogen bondings are compared with thermal energies required for their expulsion from the coordination polymers calculated with the help of Coats and Redfern’s relation of rising temperatures. Activation energy required for establishing tetramer (M-4) and dimer (M-2) in coordination sphere by counter ion using same synthetic route is found to be comparable (~37.48±1 kJ mol-1). Quantitized energies from TG-DTA data for valence tautomers of redox active ligands play significant role in formation of resultant model compound. viz. tetramer, dimer of dimer and trimer. The role of oxo, acetato and spin carrier ligands in model cluster compounds are proposed with respect to their expulsion energies.

The reaction of CuCl with 2HNQ, ( viz. 2- hydroxy- 1,4- naphthoquinone), in methanol results in [Cu-2( II, II)(4HNSQ)(2)(ONQ)(2)(H2O)(4)], Cu- 3 complex; [ where ONQ is the deprotonated oxidized form of ligand ( viz. 2- oxido- 1,4- naphthoquinone) and 4HNSQ one electron reduced tautomeric form of the ligand (i.e. 4- hydroxy - 1,2- naphthosemiquinone)]. The mixed valent redox ligation is confirmed in [ 9] by us. In present report complex Cu- 3 investigated by variable temperature magnetic susceptibility measurements ( SQUID), X and Q- band EPR, DSC and CV techniques. A break is observed in the chi(-1)(m) vs. T plot similar to 200 K in Cu- 3 which is attributed to a phase transition. In Cu- 3 a quintet state ( S= 2) is populated above 200 K by the molecular association of two exo Cu( II)( 4HNSQ) units via hydrogen bonding between Cu(ONQ) unit of endo ligands in dimer. Magnetic susceptibility data is treated with tetramer model with S= 1/2,1/2,1/2,1/2. The interdimer triplet- triplet interaction ( J) in two [ Cu( 4HNSQ)] units and intradimer ( zJ(1)) interaction between [ Cu( II)( 4HNSQ)] are best fitted with J= -50 cm(-1) and zJ(1)= 28 cm(-1), respectively, using g= 2.2. 'Quintet- triplet' phase transition occurs with an enthalpy change of 31.83 kJ mol(-1) estimated from DSC. Cu( II)double left right arrow Cu( I) and NSQ double left right arrow CAT redox couples at E-1/2= 0.68 V and E-1/2 = -1.12 V, respectively are result of exo ligands and Cu( II) ions interaction, while shifts of ligand based peaks viz. NQ -> NSQ and NSQ double left right arrow CAT at - 0.44 and - 0.67 V towards positive potential on complexation are due to electron transfer interactions between endo ligand and Cu( II) ion.

Amphi-syn stereoisomers with 62: 38 compositional ratio existing in 3-nitrolawsoneoxime [ S. Y. Rane et al., 1990] leads to two configurational forms in its copper (II) complex 1 viz. [Cu(NO2-LwOx)(2)] center dot 3H(2)O. The D-4h: D-2h geometries of 1 have been detected in 70: 30 ratio from solution EPR spectra. Line width alternation effect with superimposition of metal-ligand hyperfine splits lead to anisotropic magnetic parameters. Best fitted bonding parameters of 1 are compared with (OO)-O-boolean AND and (NO)-O-boolean AND donor complexes.

Self-assemblies of 2-hydroxy-1,4-naphthoquinone (HNQ) have been investigated using the (HNQ) n (n=1–4) series as modeled systems employing ab initio Hartree–Fock calculations. The energetics and charge distribution in these molecular systems are presented. As revealed from the electron density in the highest occupied molecular orbital of the lowest energy conformers of (HNQ) n (n=1–4) the charge ‘percolates’ to the end unit of the assembly. This has been supported by the molecular electrostatic potential topography.

Supramolecular [Cu(II)(ONQ)2(H2O)2]n (1) a complex of the 2-hydroxy-1,4-naphthoquinone ligand (2HNQ), has been synthesized using CuCl2·2H2O. ONQ is the deprotonated oxidized form of the ligand (viz. 2-oxido-1,4-naphthoquinone). The complex has been characterised by X-ray crystallography, variable temperature magnetic susceptibility measurements (SQUID), EPR and CV studies. The crystal structure of 1 has been solved at 295 and 161 K. The cell volume decreases from 435.3(6) Å3 at 295 K to 427.9(6) Å3 at 161 K. The monomeric units of 1 are linked by three types of intermolecular hydrogen bondings through coordinated ONQ ligands and water molecules, which results in a supramolecular three dimensional hydrogen bonding network. The magnetic susceptibility data of 1 were best fitted with the Bonner Fisher equation with the coupling parameter J=−3.2 cm−1, indicating a weak antiferromagnetic interaction along the chain.

Syntheses of phthiocol complexes with Cu(II) in inert media resulted in anhydrous monomer Cu-4: [Cu(NQ)2] and dimer Cu-5: [Cu(NQ)(NSQ)]2, however synthesis in air generates polymeric hydrated Cu-6: [Cu(NQ)2(H2O)2]n. Media and colligation give rise to charge transfers in coordination compounds and lead to different redox ligations of 3-methyl-2-hydroxy-1,4-naphthoquinone. These redox forms are determined from quantitization of activation energies (E a) of different pyrolytic steps in TG using the rising temperature expression of Coats and Redfern. 'Tyrosinase'-type mechanism is discussed for the redox-type ligation. Characteristic six-line EPR signals of dimeric Cu-5 lead to zero field splitting parameters D=0.01608 cm-1and E=0.01576 cm-1. Cu-6 shows molecular association through hydrogen bonding. Variable temperature magnetic measurement data of Cu-6 from 6 to 300 K is fitted to the polymeric expression of Bonner and Fisher model. The best fit was obtained with antiferrromagnetic exchange coupling constantJ=-2 cm-1, g=2.2 having R=4.2·10-4.

Hartree–Fock and hybrid density functional methods have been used to determine the structure and energetics of keto and nitrosophenol tautomers of 2-hydroxy-3-methyl-1,4-naphthoquinone-1-oxime (1). The charge distribution and vibrational spectra of keto form of 1 have been studied. The structure derived from X-ray diffraction on the single crystal has also been presented. Both the theory and experiment predict that 1 exists predominantly as amphi conformer (keto form), which is 23.54 and 41.08kJmol−1 more stable relative to the anti and syn conformers, respectively. This has partly been attributed to the five-membered ring formation resulting from the N⋯H–O (2.06Å) intramolecular hydrogen bond. The X-ray determined crystal structure shows extended three-dimensional network comprising of CO⋯H intermolecular hydrogen bonds (1.87Å) as well. Quantum mechanically calculated molecular electrostatic potential investigations provide insights for the formation of supramolecular assemblies. The frequencies of the CN and CO stretching vibrations from the density functional theory agree well with those observed experimentally. The intramolecular hydrogen bonded interactions (N⋯H–O) give a broad band near 3125cm−1 in the measured infrared spectrum whereas the 3365cm−1 peak originates from the associated OH stretching.