Search

Camptothecin (CPT) and its analogs are gaining prominence for its promising anti-cancer activity and are used throughout the world for the treatment of colorectal, breast, and lung cancers in particular. Nothapodytes nimmoniana (J. Graham) Mabb. (Olacaceae), a plant native to India's Western Ghats, has been harnessed for the production of CPT. The endangered nature of its wild population has urged plant tissue culture and engineering techniques to increase CPT production in multifold levels by adapting elicitation methods using chemical stress-inducing substances called elicitors. The main objective of this study is to increase the CPT production through in vitro cell suspension culture of N. nimmoniana by treating it with 5 different biotic elicitors such as chitin, chitosan, pullulan, glutathione, and jasmonic acid. The preliminary quantification of CPT in methanolic extracts of wild N. nimmoniana revealed that the bark extracts showed higher level of CPT than the leaf extracts. Further, column chromatography technique was employed to obtain CPT with 99.25 % purity. The elemental composition and structure of the purified compound was confirmed through HR-MS and Proton NMR spectroscopy. Shake flask in vitro elicitation of CPT was observed at a maximum level in 10 % chitin treated elicited culture with a yield of 15.06 μg/150 ml culture followed by 5 % jasmonic acid amounting to 6.025 μg/150 ml of culture as compared with other elicitors and control. LC-MS/MS fragmentation analysis was utilized for the structural confirmation of CPT. In conclusion, the biotic elicitor chitin 10 % treated suspension cells of N. nimmoniana showed maximum level (11.48-fold) of CPT elicitation followed by 4.65-fold in 5 % jasmonic acid treatment as compared with other elicitors and control suspension cells.

Uropathogenic Escherichia coli (UPEC) are the most common cause of UTI, accounting for more than 90% infections in the normal and unobstructed urinary tracts. Multi-drug resistance (MDR) is an emerging threat to the mankind and hence, there is an urge to develop alternative therapies. Targeting quorum sensing (QS), a cell-cell communication process regulates various biofilm and virulence factors would be a most promising alternate which curbs the pathogenesis without killing the bacteria, unlike antibiotics. SdiA, a quorum regulator is well-known to control the behavioural changes of UPEC in establishing biofilm and virulence. Therefore, we have hypothesized that the SdiA-selective inhibitors derived from the plant, Melia dubia using the molecular docking would be a remarkable therapeutic candidate to down regulate the UPEC biofilm and virulence phenotypes. In this study, we have designed, synthesized and characterized the fructose-furoic acid ester by NMR and ESI-MS. In vitro studies revealed that the QSI-MD selectively inhibits UPEC adherence and confocal laser scanning microscopy (CLSM) analysis showed the effectiveness of QSI-MD to inhibit the UPEC biofilm. Genetic studies using qRT-PCR revealed the down-regulation of quorum sensing regulated genes (fimA, csgA, espA). Based on the findings, we could propose that the QSI-MD could possibly act through SdiA and show target-specific inhibition of biofilm and virulence. It is notable that more than 70 bacterial species execute their communication through the SdiA homologues (LuxIR system). Hence, the QSI-MD could be further developed as a broad-spectrum anti-infective drug.

A unique recyclable Pd catalyst (‘SiO2’-NH2-Pd) for Suzuki-Miyaura coupling reaction of azaheteroaryl halides is developed. The catalytic system is working under mild aqueous condition with low Pd loading and without the use of phosphine ligand. The plausible mechanism is proposed based on the formation of undesired symmetrical biaryl from the coupling reaction of azaheteroaryl chlorides due to the oxidative homocoupling of nucleophilic arylboronic acid. This catalytic system represents an attractive and promising approach for the synthesis of azaheterobiaryls with high product yields. The catalyst has demonstrated an excellent recyclability.

Indole thiosemicarbazone ligands were prepared from indole-3-carboxaldehyde and N-(un)substituted thiosemicarbazide. The Ru(η6-p-cymene) complexes [Ru(η6-p-cymene)(HL1)Cl]Cl (1) and [Ru(η6-p-cymene)(L2)]2Cl2 (2*) were exclusively synthesized from thiosemicarbazone (TSC) ligands HL1 and HL2, and [RuCl2(p-cymene)]2. The compounds were characterized by analytical and various spectroscopic (electronic, FT-IR, 1D/2D NMR, and mass) tools. The exact structures of the compounds (HL1, HL2, 1, and 2*) were confirmed by single-crystal X-ray diffraction technique. In complexes 1 and 2*, the ligand coordinated in a bidentate neutral (1)/monobasic (2*) fashion to form a five-membered ring. The complexes showed a piano-stool geometry around the Ru ion. While 2* existed as a dimer, 1 existed as a monomer, and this was well explained through free energy, bond parameter, and charge values computed at the B3LYP/SDD level. The intercalative binding mode of the complexes with calf thymus DNA (CT DNA) was revealed by spectrosc...

A series of Ru(II)-benzene organometallic compounds (1–6) constructed from [RuCl2(η6-benzene)]2 and chiral aroylthiourea ligands (L1-L6) obtained from D/L-phenylalanine, was fully characterized. The chiral complexes along with 2-propanol and NaOH effected the asymmetric hydrogenation of aromatic ketones at 82 °C within 8–10 h. The reduction reactions proceeded with excellent conversions and enantiomeric excesses (up to 99%).

A new series of p-[N,N-bis(2-chloroethyl)amino]benzaldehyde substituted chalcone derivatives were designed and synthesized, and their structures were characterized by spectroscopic techniques and single crystal XRD studies. Compounds 3a-f crystallized in the triclinic system with a centrosymmetric space group P (1) over bar, except for crystal 3c which crystallized in the monoclinic crystal system with a centrosymmetric space group P21/c. Molecular docking studies were utilized to reveal the binding mode of the derivatives to identify new tubulin inhibitors. Density functional theory calculations were performed to understand the structural and electronic properties of these chalcones. The DFT results show that the HOMOs of all the chalcones lie in the range of -5.65 to -6.17 eV and the LUMOs in the range of -2.01 to -3.21 eV. The experimental results are well supported by the theoretical structural analysis. The biological activity of these compounds showed high potency of growth inhibitory effects with sub-micromolar IC50 values ranging from 0.089 to 0.200 mu M against A549 and HepG2 cancer cell lines. Furthermore, these compounds exhibited a strong inhibitory effect on tubulin polymerization. 3e showed the highest mean activity against both the cancer cells and in tubulin inhibition. This correlated well with the theoretical results from the pharmacophore binding model. Hence, these six compounds, particularly 3e, could be considered as potential leads in the development of new anticancer agents.

A series of new chiral aroylthiourea ligands was derived from unprotected D/L-phenylalanine: (R)/(S)-2-(3-benzoylthioureido)-3-phenylpropanoic acid (L1/L2), (R)/(S)-2-(3-(thiophene-2-carbonyl)thioureido)-3-phenylpropanoic acid (L3/L4) and (R)/(S)-2-(3-(furan-2-carbonyl)thioureido)-3-phenylpropanoic acid (L5/L6). Chiral Ru(II) complexes (1–6) were obtained from the reactions between the chiral ligands (L1–L6) and [RuCl2(p-cymene)2]2 through in situ catalytic esterification of the ligand in the presence of methanol solvent. The ligands and complexes were characterized by analytical and spectral (1H NMR, 13C NMR, Mass, FT-IR, electronic) techniques. The molecular structure of the ligand L1 showed the presence of an unprotected acid group and that of the representative complexes confirmed the conversion of acid to ester. The X-ray structure of two of the complexes (3 and 6) revealed the sulfur only monodentate coordination of the aroylthiourea ligands. All the chiral complexes turned out to be efficient catalysts for the enantioselective reduction of aromatic pro-chiral ketones in the presence of 2-propanol and NaOH to produce chiral alcohols in excellent conversions (up to 99%) and enantiomeric excesses (up to 99%) within 10–12 h.

Two novel pyrazole based thiourea palladium(II) complexes, [PdCl(PPh3)(C9H8NO2S-pz)] (1) and [PdCl(PPh3)(C14H10NO2S-pz)] (2) [pz = pyrazole (C3H2N2)] have been obtained unexpectedly from chromone thiosemicarbazones (L1 and L2) and [PdCl2(PPh3)2]. The compounds have been fully characterized by physicochemical studies. The single crystal X-ray diffraction and spectral studies revealed square planar geometry for the complexes. The conversion of chromone thiosemicarbazone into pyrazole based thiourea might have happened through coordination to palladium(II) ion after enolization, Michael addition and ring opening followed by cyclization. To the best of our knowledge, this is the first report for the conversion of chromone thiosemicarbazone into pyrazole based thiourea moiety. Plausible mechanism was proposed based on the spectroscopic studies. Calf thymus (CT) DNA binding of the compounds was explored using various spectroscopic and molecular docking methods. DNA cleavage studies suggested that complexes 1 and 2 had the capacity to cleave the supercoiled DNA (pUC19) to its naked form. In vitro cytotoxic property of the ligands and complexes has been evaluated against three human cancer cells such as A549, HepG-2 and U937. Complex 2 exhibited potent cytotoxic activity against HepG-2 cells with the IC50 value of 10.4 μM. In addition, mechanistic studies showed that complex 2 induced apoptosis through mitochondrial signaling pathway in HepG-2 cells. Beneficially, complex 2 showed less toxicity against human lung (IMR90) normal cells and hence it emerges as a potential candidate for further studies.

The reactions of [RuCl2(η6-C6H6)]2 with chiral aroylthiourea ligands yielded pseudo-octahedral half-sandwich “piano-stool” complexes. All the Ru(II) complexes were characterized by analytical and spectral (UV-visible, FT-IR, 1H NMR and 13C NMR) studies. The molecular structures of the ligands (L2 and L4) and the complexes (2, 4 and 5) were confirmed by single crystal XRD. All the complexes were successfully screened as catalysts for the asymmetric transfer hydrogenation (ATH) of ketones using 2-propanol as the hydrogen source in the presence of KOH. The ATH reactions proceeded with excellent yields (up to 99%) and very good enantioselectivity (up to 99% ee). The scope of the present catalytic system was extended to substituted aromatic ketones and few hetero-aromatic ketones. Density functional theory (DFT) calculations predicted non-classical, concerted transition states for the ATH reactions. The catalytic activity of Ru–benzene complexes toward asymmetric reduction of ketones was significantly higher compared to that of p-cymene complex analogues. Such enhanced efficiency and product selectivity of Ru–benzene complexes compared to those of Ru–p-cymene complexes were rationalized by the computational study.

The new chiral ligands (R)-/(S)-N-((1-phenylethyl)carbamothioyl)benzamide (L1/L2), (R)-/(S)-N-((1-phenylethyl)carbamothioyl)thiophene-2-carboxamide (L3/L4), and (R)-/(S)-N-((1-phenylethyl)carbamothioyl)furan-2-carboxamide (L5/L6) were synthesized, characterized, and used to prepare novel chiral Ru(II) complexes. The chiral Ru(II) complexes 1–6 were obtained from reactions between the chiral ligands L1–L6 and [RuCl2(p-cymene)2]2. The complexes were characterized by analytical and spectroscopic (NMR, FT-IR, electronic) techniques. The solid-state structures of the ligands L1 and L3 and complexes 1, 4, and 6 were determined by single-crystal X-ray diffraction methods. In all of the complexes, the ligand is bound to the Ru(II) center only via the sulfur donor atom. This monodentate coordination of the acylthiourea ligands was observed for the first time with ruthenium. The Ru(II) complexes 1–6 all act as efficient catalysts for the asymmetric transfer hydrogenation of aromatic ketones in the presence of 2-pro...

We have developed a heterogenized catalyst (‘SiO 2 ’–NH 2 –Ru III ) by the immobilization of [Ru(acac) 2 (CH 3 CN) 2 ]PF 6 on SiO 2 . The catalyst was characterized by SEM, solid state NMR, EPR, FT-IR, ICP, and BET surface area analyses. ‘SiO 2 ’–NH 2 –Ru III catalyzed the selective oxidation of alcohols with periodic acid in water at room temperature. This protocol was applicable to the controlled oxidation of structurally diverse primary and secondary alcohols. The catalyst could be quantitatively recovered and reused up to six cycles without significant loss of catalytic activity.

Comparison of experimental and theoretical parameters pertaining to structural and spectral properties of two nickel(II) complexes containing triphenylphosphine and 5-methyl-N-(2-mercaptophenyl)salicylideneimine (1) or 5-chloro-N-(2-mercaptophenyl)salicylideneimine (2) are presented. The calculated structural results of these complexes show that the DFT can well reproduce the structure of title compounds. The UV, IR and NMR spectra of the title compounds are determined using both experimental and theoretical methods. The optical absorption properties of the title compounds are calculated using time-dependent density functional theory method (TD-DFT). The IR spectra are calculated from the harmonic vibrational frequencies at the ground-state geometry of the title-compounds. The NMR spectra are calculated using the gauge-independent atomic orbital (GIAO) method. The results calculated using theoretical methods coincide well with the experimental results.

Square planar palladium(II) complexes of the type [Pd(L)(PPh3)] (1–6) (where L is the dianion of N-(2-mercaptophenyl)salicylideneimine or 5-substituted-N-(2-mercaptophenyl)salicylideneimine or N-(2-mercaptophenyl)naphthylideneimine) have been synthesised from the reactions between [Pd(PPh3)4] and H2L in dichloromethane–ethanol mixture. The new complexes have been characterized by analytical and spectral (electronic, IR, 1H, 13C{1H} and 31P{1H} NMR spectroscopy) techniques. The structures of three complexes (1, 2 and 6) have been solved by single-crystal X-ray diffraction experiments which indicate square planar coordination geometries around palladium(II) by O, N, S and P donor atoms. The palladium(II) complexes (1–6) exhibited good catalytic activity in Suzuki–Miyaura cross-coupling reaction between phenylboronic acid and 4-bromotoluene in N,N-dimethylacetamide at 100 °C. Complex 3 (1 mol%) was found to be the most active and hence was used for probing the scope of possible substrates. Heterocyclic boronic acid and heterocyclic aryl bromides have also been used as substrates to provide heterocyclic biaryls.

Air stable Ni(II) and Pd(II) complexes viz. [Ni(LS)(P(OEt)3)] (1), [Ni(LN)(P(OEt)3)] (2), [Pd(LS)(P(OEt)3)] (3) and [Pd(LN)(P(OEt)3)] (4) [where LS and LN are dianions of N–(2–mercaptophenyl)salicylideneimine and N–(2–mercaptophenyl)naphthylideneimine respectively] have been synthesized and characterized by analytical and spectral (electronic, FT–IR, 1H, 13C and 31P NMR) methods. The 1H–31P HMBC spectrum established the coupling of phosphorus with the azomethine proton of the Schiff base and the aliphatic protons of triethylphosphite. Novel Ni(II) and Pd(II) complexes exhibited good catalytic activity in Kumada–Tamao–Corriu and Suzuki–Miyaura coupling reactions respectively.

2-[(E)-{(1S,2R)-1-hydroxy-1-phenylpropan-2-ylimino}methyl]phenol has been synthesized and its influence on corrosion of mild steel in 1 M HCl solution has been studied by means of weight loss and electrochemical measurements under various circumstances. The inhibitor showed a maximum of 91 % of inhibition efficiency at 100 ppm. Interestingly, the inhibition efficiency has decreased on increasing the inhibitor concentration. This abnormal behavior is attributed to the release of phenolic hydrogen from the molecule. The mechanism of corrosion inhibition follows Langmuir adsorption isotherm. The negative ∆G ads indicates the spontaneous adsorption of the inhibitor on mild steel surface. Potentiodynamic polarization studies show that it is a mixed type inhibitor with predominant cathodic inhibition. UV–Visible spectroscopy of the inhibitor and inhibitor adsorbed on the mild steel confirmed the chemical interaction of the inhibitor with the metal surface.

A series of 4-substituted N-(2-mercaptophenyl)salicylideneimine Schiff bases were synthesized and investigated for corrosion inhibition of mild steel in hydrochloric acid medium. Inhibition through adsorption mechanism is proposed for these inhibitors, which is well supported by electrochemical impedance spectroscopy, the Langmuir adsorption isotherm and Scanning Electron Microscope morphologies of inhibited and uninhibited mild steel specimens. The negative ∆Gads indicates the spontaneous adsorption of the inhibitor on a mild steel surface. Among all the examined inhibitors, 5-bromo-N-(2-mercaptophenyl)salicylideneimine showed a higher inhibition efficiency. In order to reveal the usefulness of these Schiff bases as corrosion inhibitors under various circumstances, weight loss measurements were performed at various temperatures, acid concentrations and immersion times.

Reactions of H2L with [RuHCl(CO)(PPh3)3] in toluene gives [Ru(L)(CO)(PPh3)2] (L = binegative tridentate ONS donor ligand derived from salicylaldehyde/4-substituted salicylaldehyde/2-hydroxy-1-naphthaldehyde and o-aminothiophenol) at room temperature. All the complexes were characterized by elemental analyses and UV–Visible, FT-IR, 1H, 13C and 31P NMR spectroscopic methods. 1H–1H COSY and 1H–31P HMBC spectra of [Ru(L4)(CO)(PPh3)2] have been studied. 1H–31P HMBC spectrum established the coupling of phosphorus atoms with azomethine proton. The single crystal X-ray analysis of [Ru(L5)(CO)(PPh3)2] revealed that Schiff base ligand is coordinated to the metal center, via dissociation of the two acidic protons, as a dianionic tridentate ONS donor and that ruthenium(II) ion adopts octahedral coordination with the phosphorus atoms in trans-disposition. Ruthenium complexes have been used in conjunction with N-methylmorpholine-N-oxide (NMO) for the catalytic oxidation of various alcohols at room temperature. Benzylic primary and secondary alcohols are oxidized in good to excellent yields, and aliphatic and cyclic alcohols give carbonyl compounds in moderate yields.

A series of norephedrine-based Schiff bases (1a–6a and 1b–6b) were synthesized by reacting substituted salicylaldehydes with d-norephedrine or l-norephedrine. The structure of these compounds was confirmed by elemental analyses and spectroscopic techniques. The molecular structures of 5a and 6a have been determined by X-ray crystallography, which revealed that the compounds are in the oxoamino form, with bent intramolecular N-H···O (N···O ≈ 2.58 A) hydrogen bonds and that they are associated in dimers bridged by linear intermolecular O-H···O (O···O ≈ 2.69 A) hydrogen bonds. The density functional theory calculations on 5a confirmed that the oxoamino form is more stable than the phenolimino form by 12.2 kcal/mol. All the compounds were evaluated for their antibacterial activity using resazurin dye as indicator by twofold dilution method against four bacteria namely, Bacillus subtilis (NCIM2718), Staphylococcus aureus (NCIM5021), Escherichia coli (NCIM2931), and Proteus vulgaris (NCIM2813).

Six different ruthenium(III) complexes of Schiff bases derived from 2-hydroxy-1-naphthaldehyde and o-aminophenol/o-aminothiophenol have been synthesized. The compounds with the general formula [RuX(EPh3)2(L)] (X = Cl or Br; E = P or As; L = bifunctional tridentate ONO/ONS donor Schiff base ligand) were characterized by infrared, electronic, electron paramagnetic resonance spectroscopy and elemental analyses. Spectroscopic investigation reveals coordination of Schiff base ligand through ONO/ONS donor atoms and octahedral geometry around ruthenium metal. Redox property of complexes has been examined by using cyclic voltammetry. The catalytic oxidation property of ruthenium(III) complexes were also investigated.

Mononuclear nickel(II) complex, viz. [Ni(L)(PPh 3)] (where L is dianion of N-(2-mercaptophenyl)-4-methoxysalicylideneimine) has been synthesized and characterized by means of elemental analysis, electronic, IR and NMR [ 1H, 13C{ 1H} and 31P{ 1H}, DEPT, 1H- 1H COSY, ge-HSQC, ge-HMBC] spectroscopic techniques. Structural analysis of the complex by single crystal X-ray crystallography indicated the presence of square planar coordination geometry (ONSP) about nickel. One of the phenyl rings of triphenylphosphine involve in CH?? interactions with H6b, H13 and H32 to form a three dimensional network which stabilizes the structure of complex. � 2010 Elsevier B.V.

Ruthenium acts as a good catalyst for the racemization reaction of secondary alcohols and amines. Ruthenium-catalyzed racemization is coupled with enzymatic kinetic resolution to prepare chiral compounds in 100% theoretical yield. Ten ruthenium complexes ( 1 – 10 ) act as a good catalyst the for racemization reaction and are also compatible with DKR process. Two other ruthenium complexes [RuCl 2 (PPh 3 ) 3 ] and [Cp ∗ RuCl(COD)] are active for racemization reaction but their successful compatibility with DKR has not yet been reported. Ru/γ-Al 2 O 3 and Ru–HAP are the heterogeneous catalysts used for the racemization reaction. They have also not been employed for DKR process. Polymer supported ruthenium is employed as a reusable racemization catalyst for aerobic DKR of alcohols.

Five mononuclear nickel(II) complexes, viz. [Ni(L1)(PPh3)] (1), [Ni(L2)(PPh3)] (2), [Ni(L3)(PPh3)] (3), [Ni(L4)(PPh3)] (4) and [Ni(L5)(PPh3)] (5) (where L1, L2, L3, L4 and L5 are dianions of N-(2-mercaptophenyl)salicylideneimine, 5-methyl-N-(2-mercaptophenyl)salicylideneimine, 5-chloro-N-(2-mercaptophenyl)salicylideneimine, 5-bromo-N-(2-mercaptophenyl)salicylideneimine and N-(2-mercaptophenyl)naphthylideneimine, respectively), have been synthesized and characterized by means of elemental analysis, electronic, IR, 1H, 13C and 31P NMR spectroscopy. Single crystal X-ray analysis of two of the complexes (1 and 5) has revealed the presence of a square planar coordination geometry (ONSP) about nickel. The crystal structures of the complexes are stabilized by intermolecular π–π stacking between the ligands (L) and by various C–H···π interactions.

The novel title catalyst is successfully employed to the selective oxidation of primary and secondary alcohols with periodic acid.

Ruthenium acts as a good catalyst for the racemization reaction of secondary alcohols and amines. Ruthenium-catalyzed racemization is coupled with enzymatic kinetic resolution to prepare chiral compounds in 100% theoretical yield. Ten ruthenium complexes ( 1 – 10 ) act as a good catalyst the for racemization reaction and are also compatible with DKR process. Two other ruthenium complexes [RuCl 2 (PPh 3 ) 3 ] and [Cp ∗ RuCl(COD)] are active for racemization reaction but their successful compatibility with DKR has not yet been reported. Ru/γ-Al 2 O 3 and Ru–HAP are the heterogeneous catalysts used for the racemization reaction. They have also not been employed for DKR process. Polymer supported ruthenium is employed as a reusable racemization catalyst for aerobic DKR of alcohols.

The Ni(II) atom in the title complex, [Ni(C(13)H(8)BrNOS)(C(18)H(15)P)], is coordinated by the N, O and S atoms of the dianionic tridentate ligand, and its square-planar geometry is completed by a phosphane P atom. The dihedral angle between the aromatic rings in the 4-bromo-2-[(2-sulfido-phen-yl)imino-meth-yl]phenolate ligand is 2.01 (14)°. The most prominent feature of the packing is the presence of supra-molecular chains aligned along the a axis, mediated by C-H⋯S inter-actions.