Evidence of Two Oxidative Reaction Steps Initiating Anaerobic Degradation of Resorcinol (1,3-Dihydroxybenzene) by the Denitrifying Bacterium Azoarcus anaerobius

The denitrifying bacterium Azoarcus anaerobius LuFRes1 grows anaerobically with resorcinol (1,3-dihydroxybenzene) as the sole source of carbon and energy. The anaerobic degradation of this compound was investigated in cell extracts. Resorcinol reductase, the key enzyme for resorcinol catabolism in fermenting bacteria, was not present in this organism. Instead, resorcinol was hydroxylated to hydroxyhydroquinone (HHQ; 1,2,4-trihydroxybenzene) with nitrate or K₃Fe(CN)₆ as the electron acceptor. HHQ was further oxidized with nitrate to 2-hydroxy-1,4-benzoquinone as identified by high-pressure liquid chromatography, UV/visible light spectroscopy, and mass spectroscopy. Average specific activities were 60 mU mg of protein⁻¹ for resorcinol hydroxylation and 150 mU mg of protein⁻¹ for HHQ dehydrogenation. Both activities were found nearly exclusively in the membrane fraction and were only barely detectable in extracts of cells grown with benzoate, indicating that both reactions were specific for resorcinol degradation. These findings suggest a new strategy of anaerobic degradation of aromatic compounds involving oxidative steps for destabilization of the aromatic ring, different from the reductive dearomatization mechanisms described so far.     

A strictly anaerobic nitrate-reducing bacterium growing with resorcinol and other aromatic compounds

With resorcinol as sole source of energy and organic carbon, two stains of gram-negative, nitrate-reducing bacteria were isolated under strictly anaerobic conditions. Strain LuBRes1 was facultatively anaerobic and catalase- and superoxide dismutase-positive. This strain was affiliated with Alcaligenes denitrificans on the basis of substrate utilization spectrum and peritrichous flagellation. Strain LuFRes1 could grow only under anaerobic conditions with oxidized nitrogen compounds as electron acceptor. Cells were catalase-negative but superoxide dismutase-positive. Since this strain was apparently an obligate nitrate reducer, it could not be grouped with any existing genus. Resorcinol was completely oxidized to CO₂ by both strains. Neither an enzyme activity reducing or hydrolyzing the resorcinol molecule, nor an acyl-CoA-synthetase activating resorcylic acids or benzoate was detected in cell-free extracts of cells grown with resorcinol. In dense cell suspensions, both strains produced a compound which was identified as 5-oxo-2-hexenoic acid by mass spectrometric analysis. This would indicate a direct, hydrolytic cleavage of the resorcinol nucleus without initial reduction.     

Effect of shock-loading of heavy metals on total organic carbon and phosphate removal in an anaerobic-aerobic activated sludge process

The effect of shock-loading of zinc, copper and cadmium ions on the removal of total organic carbon (TOC) and phosphate in an anaerobic-aerobic activated sludge process was investigated. TOC removal was not sensitive to shock-loading of Zn²⁺ and Cd²⁺ ions, and complete removal was achieved even at 20 mg Zn²⁺/l and 20 mg Cd²⁺/l. However, with over 1 mg Cu²⁺/1 TOC removal efficiency decreased. PO _inf4 ^sup3- removal, in contrast, was extremely sensitive to these metal ions, with the threshold being 1 mg Zn²⁺/l and 1 mg Cd²⁺/l. Higher concentrations adversely affected PO _inf4 ^sup3- removal. Copper again proved detrimental; no PO _inf4 ^sup3- removal was achieved even at 1 mg Cu/l. These results highlight the sensitivity of the removal efficiencies of TOC and PO _inf4 ^sup3- to shock loadings of these heavy metals.Y.P. Ting is with the Department of Chemical Engineering, National University of Singapore, Kent Ridge, 0511, Singapore; H. Imai and S. Kinoshita are with the Department of Chemical Process Engineering, Hokkaido University, Sapporo 060, Japan.     

Transformation of Chlororesorcinol by the Hydrocarbonoclastic Yeasts Candida maltosa,Candida tropicalis,and Trichosporon oivide

The inhibitory effects of chlorinated monoaromatic compounds on three hydrocarbonoclastic yeasts grown on glucose or resorcinol were examined. At concentrations of 1.0 M, all of the monoaromatic compounds were inhibitory. When the concentration of chlororesorcinol was significantly reduced (0.0005 M), the inhibition to each yeast was minimized. Extracts of the cultures of yeasts growing on resorcinol plus chlororesorcinol were analyzed for residual resorcinol and chlororesorcinol with high pressure liquid chromatography. Neither compound was detected in the culture broth of Candida maltosa, but several unidentified compounds were present. Only chlororesorcinol was detected in the culture broth of Trichosporon oivide, and both resorcinol and chlororesorcinol were present in extract from cultures of C. tropicalis. Cultures of C. maltosa grown on resorcinol-yeast nitrogen base, washed and suspended in phosphate buffer and subsequently incubated with chlororesorcinol, turned the culture broth a distinct pink color. The data indicate that C. maltosa has the potential to co-metabolize chlororesorcinol. Received: 28 January 1997 / Accepted: 7 March 1997     

Proliferation inhibition of novel diphenylamine derivatives

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most widely used drugs in the world but some NSAIDs such as diclofenac and tolfenamic acid display levels of cytotoxicity, an effect which has been attributed to the presence of diphenylamine contained in their structures. A novel series of diphenylamine derivatives were synthetised and evaluated for their cytotoxic activities and proliferation inhibition. The most active compounds in the cytotoxicity tests were derivative 6g with an IC₅₀ value of 2.5 ± 1.1 × 10⁻⁶ M and derivative 6f with an IC₅₀ value of 6.0 ± 3.0 × 10⁻⁶ M (L1210 cell line) after 48 h incubation. The results demonstrate that leukemic L1210 cells were much more sensitive to compounds 6f and 6g than the HEK293T cells (IC₅₀ = 35 × 10⁻⁶ M for 6f and IC₅₀ > 50 × 10⁻⁶ M for 6g) and NIH-3T3 (IC₅₀ > 50 × 10⁻⁶ M for both derivatives). The IC₅₀ values show that these substances may selectively kill leukemic cells over non-cancer cells. Cell cycle analysis revealed that a primary trend of the diphenylamine derivatives was to arrest the cells in the G₁-phase of the cell cycle within the first 24 h. UV–visible, fluorescence spectroscopy and circular dichroism were used in order to study the binding mode of the novel compounds with DNA. The binding constants determined by UV–visible spectroscopy were found to be in the range of 2.1–8.7 × 10⁴ M⁻¹. We suggest that the observed trend for binding constant K is likely to be a result of different binding thermodynamics accompanying the formation of the complexes.     

A new method for isolation of saprophytic cultures ofClaviceps fusiformis from sclerotia

The proposed method includes primary and secondary treatments. Of the various disinfectants tested, 1-propanol and 1-butanol as a primary treatment and phenol, resorcinol, HgCl₂ or NaCl as a secondary treatment completely eliminated the contamination hazard. 1-Butanol and phenol were not useful disinfectants since they inhibited the growth ofC. fusiformis along with the other contaminants. Primary and secondary treatment of sclerotia with 1-propanol and resorcinol, respectively, produced the maximum of stable cultures. Out of 120 cultures tested, 5 cultures demonstrated an appreciable yield of alkaloids under submerged cultural conditions.     

Effects of elevated CO2 and nitrogen addition on soil organic carbon fractions in a subtropical forest

Aims

The aim of this study was to investigate the effects of elevated CO₂ concentration and nitrogen addition on soil organic carbon fractions in subtropical forests where the ambient N deposition was high.

Methods

Seedlings of typical subtropical forest ecosystems were transplanted in ten open-top chambers and grown under CO₂ and nitrogen treatments. The treatments included: 1) elevated CO₂ (700?μmol?mol^-1); 2) N addition of 100?kg NH₄NO₃ ha^-1?yr^-1; 3) combined elevated CO₂ and N addition; and 4) control. We measured soil total organic carbon (TOC), particulate organic carbon (POC), readily oxidizable organic carbon (ROC), and microbial biomass carbon (MBC).

Results

Results showed that elevated CO₂ alone did not significantly affect soil TOC, POC and ROC after 4?years of treatment, but increased soil MBC and soil respiration compared to the control. N addition alone had no significant effect neither on soil TOC, POC and ROC, but decreased MBC and soil respiration over time. However, the elevated CO₂ and N addition together significantly increased soil POC and ROC, and had no significant effect on soil MBC.

Conclusions

This study indicated that even in N-rich subtropical forest ecosystems, inputs of N are still needed in order to sustain soil C accumulation under elevated CO₂.     

Anaerobic co-digestion of table olive debittering & washing effluent, cattle manure and pig manure in batch and high volume laboratory anaerobic digesters: effect of temperature

The prospective of table olive debittering & washing Effluent (DWE) as feed stock wastewater for anaerobic digestion (AD) systems was investigated in batch and continuous systems together with cattle and pig manures. While DWE considered unsuitable for biological treatment methods due to its unbalanced nature, the co-digestion of the wastewaters resulted in a 50% increase in the methane production/gram volatile solids_added (CH₄/gVS_added), accompanied by 30% phenol reduction and 80% total organic carbon removal (TOC). pH increase during the co-digestion period was not identified as an inhibitory factor and all reactors were able to withstand this operational condition change. Moreover, no volatile fatty acid (VFA) accumulation was observed, indicating that the reactors were not operating under stress-overloading state. Under thermophilic conditions a 7% increase on the TOC removal efficiency was achieved when compared to the mesophilic systems while, under mesophilic conditions phenolic compounds reduction was 10% higher compared to the thermophilic systems.     

The effect of chemical fertilizer on soil organic carbon renewal and CO2 emission—a pot experiment with maize

Background and Aims

Previous studies have clearly shown substantial increases of soil organic carbon (SOC) in agricultural soils of Yellow River reaches. Those soils did not receive organic fertilizer input, but did receive chemical fertilizer inputs. Thus, to investigate the hypothesis that the observed SOC increases were driven by chemical fertilizer additions, a maize pot experiment was conducted using a Fluvisol that developed under C₃ vegetation in the Yellow River reaches.

Methods

Using the natural ¹³C abundance method we calculated the SOC renewal ratio (C _renewal), and separated total soil organic carbon (TOC) into maize-derived soil organic carbon (SOC_maize) and original soil organic carbon (SOC_original). Carbon dioxide fluxes and microbial biomass carbon (MBC) were determined by closed chamber method and fumigation-extraction method, respectively. The experiment included five treatments: (1) NPK: application of chemical fertilizer NPK; (2) NP, application of chemical fertilizer NP; (3) PK: application of chemical fertilizer PK; (4) NK, application of chemical fertilizer NK; and (5) CK: unfertilized control.

Results

Fertilization increased maize biomass (including grain, straw and root), TOC, C _renewal, SOC_maize, maize-derived carbon (MDC: including SOC_maize, and root and stubble biomass carbon) and MBC, and these values among the treatments ranked NPK>NP>PK>NK>CK. The C _renewal was 5.54–8.50% across the treatments. Fertilization also increased soil CO₂ emission (including root respiration and SOC_original decomposition), while the SOC_original decomposition during the maize growing season only amounted to 74.0–93.4 and 33.5–46.1% of SOC_maize and MDC among the treatments, respectively. Thus input was larger than export, and led to SOC increase. Maize grain and straw biomass were positively and significantly correlated with soil δ¹³C, TOC, C _renewal, SOC_maize, MDC and MBC.

Conclusions

The study suggests that chemical fertilizer application could increase C _renewal by increasing crop-derived C and accelerating original SOC decomposition, and that as long as a certain level of crop yield or aboveground biomass can be achieved, application of chemical fertilizer alone can maintain or increase SOC level in Fluvisol in the Yellow River reaches.     

Sterilization effects of a TiO<Subscript>2</Subscript> photocatalytic film against a<Emphasis Type="Italic">Streptococcus mutans</Emphasis> culture

Streptococcus mutans is one of the more significant pathogens involved in the development of dental caries in humans. The purpose of this research was to design a TiO₂-coated dental instrument and to determine the bactericidal effects of the instrument onS. mutants. TiO₂ photocatalytic films were prepared by the low-pressure metal-organic chemical vapor deposition (LPMOCVD) method using titanium tetraisopropoxide (TTIP) as precursor. The photocatalytic reaction was carried out on a TiO₂-coated pyrex petri dish with an ultraviolet (UV) light emitting diode (LED) illuminator or a fluorescent lamp light source. Our data indicates that the relative survival ratio ofS. mutans when plated onto TiO₂ photocatalytic films and under exposure to UV-A light for 15 min was 0.01%. In addition, a fluorescent lamp light source also had bactericidal effects on theS. mutans plated TiO₂ photocatalytic films. These results indicate that TiO₂-coated dental materials or devices may be useful in dental treatments for the prevention of carious or enamel demineralization.     

Phenolic compounds inhibit the aldose reductase enzyme from the sheep kidney

Aldose reductase (AR) is the key enzyme for the polyol pathway and responsible for sorbitol accumulation during the hyperglycemia. The present article focuses on the role of phenol, pyrogallol, hydroquinone, resorcinol, catechol, and phloroglucinol in in vitro inhibition of AR. For this purpose, AR was purified from the sheep kidney with 5.33 EU mg^?1 specific activity and 0.64% yield using several chromatographic methods. Various concentrations of the compounds were tested on in vitro AR activity. IC₅₀ values were found for phenol, pyrogallol, hydroquinone, resorcinol, catechol, and phloroglucinol as 6.5, 1.13, 5.45, 2.21, 1.8, and 2.09 mM, respectively, and their K_i constant was calculated as 3.45 ± 0.92, 0.96 ± 0.28, 3.07 ± 0.46, 1.59 ± 0.43, 2.5 ± 0.35, and 2.54 ± 0.45 mM, respectively. Pyrogallol showed better inhibitory effect compared to the other compounds. The inhibition mechanisms of all compounds were noncompetitive. In the presents study, in vitro AR inhibition was examined by the phenolic compounds.     

Degradation and Mineralization of Phenol Compounds with Goethite Catalyst and Mineralization Prediction Using Artificial Intelligence

The efficiency of phenol degradation via Fenton reaction using mixture of heterogeneous goethite catalyst with homogeneous ferrous ion was analyzed as a function of three independent variables, initial concentration of phenol (60 to 100 mg /L), weight ratio of initial concentration of phenol to that of H₂O₂ (1: 6 to 1: 14) and, weight ratio of initial concentration of goethite catalyst to that of H₂O₂ (1: 0.3 to 1: 0.7). More than 90 % of phenol removal and more than 40% of TOC removal were achieved within 60 minutes of reaction. Two separate models were developed using artificial neural networks to predict degradation percentage by a combination of Fe³⁺ and Fe²⁺ catalyst. Five operational parameters were employed as inputs while phenol degradation and TOC removal were considered as outputs of the developed models. Satisfactory agreement was observed between testing data and the predicted values (R² _Phenol = 0.9214 and R²TOC= 0.9082).     

Reduction of the nitrogen and carbon content in swine waste with algae and bacteria

Animal waste causes environmental problems like eutrophication of ground and surface water or the pollution of the atmosphere because of its high NH₄ ⁺ content. The aim of our study was to fix the nitrogen of swine waste as biomass. Therefore, an isolated alga, Chlorella sp., and bacteria naturally living in liquid manure were grown in batch cultures (containing diluted swine waste supplied with a nutrient solution) and continuous cultures (undiluted liquid manure) to achieve reduction of NH₄ ⁺ and total organic carbon (TOC) contents. For continuous cultivation, a photobioreactor of our own design was used. The batch cultivation of Chlorella sp. and bacteria in swine waste resulted in good growth of both groups of organisms and in a reduction of 25% NH₄ ⁺ and 80% TOC. In the continuous cultivation a steady state was not achieved owing to a change in the composition of the bacterial population. NH₄ ⁺ was totally removed, but NO₂ ⁻ (up to 100 mM) was transiently released. NO₃ ⁻ was not detected. These effects might be explained by the presence of heterotrophic nitrifiers, which are able to oxidize NH₄ ⁺ to NO₂ ⁻ and to reduce NO₂ ⁻ to gaseous compounds. Received: 21 January 1999 / Received revision: 9 March 1999 / Accepted: 14 March 1999     

Total Organic Carbon (TOC) of Lake Water During the Holocene Inferred from Lake Sediments and Near-infrared Spectroscopy (NIRS) in Eight Lakes from Northern Sweden

The aim of this study is to infer past changes in total organic carbon (TOC) content of lake water during the Holocene in eight boreal forest, tree-limit and alpine lakes using a new technique – near-infrared spectroscopy (NIRS). A training set of 100 lakes from northern Sweden covering a TOC gradient from 0.7 to 14.9 mg l⁻¹ was used to establish a relationship between the NIRS signal from surface sediments (0–1 cm) and the TOC content of the water mass. The NIRS model for TOC has a root mean squared error (RMSECV) of calibration of 1.6 mg l⁻¹ (11% of the gradient) assessed by internal cross-validation (CV), which yields an R²_cv of 0.61. The results show that the most dramatic change among the studied lakes occurs in both tree-line lakes around 1000 yrs BP when the TOC content decreases from ca. 7 to 3 mg l⁻¹ at the present, which is probably due to a descending tree-limit. The TOC content in the alpine lakes shows a declining trend throughout most of the Holocene indicating that TOC may be more directly correlated to climate in alpine lakes than forest lakes. All boreal forest lakes show a declining trend in TOC during the past 3000 yrs with the largest amplitude of change occurring in the lake with a connected mire. The results indicate that a change to a warmer and more humid climate can increase the TOC levels in lakes, which in turn may increase the saturation of CO₂ in lake waters and the emission of CO₂ to the atmosphere.     

PHACOTUS LENTICULARIS (CHLAMYDOMONADALES,PHACOTACEAE) ZOOSPORES REQUIRE EXTERNAL SUPERSATURATION OF CALCIUM CARBONATE FOR CALCIFICATION IN CULTURE1,2

In nature, zoospores of the chlamydophycean genus Phacotus Perty usually have a calcified lorica. The only cultured species, Phacotus lenticularis (Ehrenberg) Stein, did not readily calcify in artificial media. To overcome this deficiency, we developed an artificial culture medium (N-HS) in which Phacotus lenticularis formed mineralized loricae, as under natural conditions. Calcification of Phacotus (strain Krienitz 91/1) was achieved in a medium containing the ionic concentrations found in natural habitats (i.e. Lake Haussee and Lake Stechlin), hard-water lakes of the Baltic Lake District (Germany). The N-HS medium contained extremely low phosphate concentrations and high calcium and magnesium concentrations compared with common culture media, but the concentrations were similar to those in the lakes. Calcium carbonate in N-HS medium was dissolved up to the saturation concentration (saturation index = 1). Supersaturation was achieved by the addition of ultra-alkaline compounds (Na₂S_iO₃ or NaOH). The medium with the highest super-saturation had a saturation index of 118 and was extremely supersaturated with respect to calcium carbonate. In that medium and in modified media with less of the sodium compounds (lower supersaturations), calcification of zoospores was observed. To determine the effects of sodium and silicon compounds on calcification, various other silicon and sodium compounds were tested but were shown to be ineffective. In conclusion, calcification of Phacotus lenticularis depends directly on the degree of calcium carbonate supersaturation of the medium, but the fundamental mineralization pattern does not. Our study shows that calcification in Phacotus lenticularis can be triggered and controlled by supersaturation of calcium carbonate.     

Anaerobic treatment of wastewater from a food-manufacturing plant with a low concentration of organic matter and regeneration of usable pure water

Wastewater from a food-manufacturing plant with a low concentration of organic matter below 100 mg/l TOC was first treated at 37°C in an anaerobic fluidized-bed reactor (AFBR) or in an upflow anaerobic sludge blanket (UASB). The TOC removal efficiency in both reactors decreased from 85% to 65% as the influent TOC concentration decreased from 100 to 35 mg/l at a hydraulic retention time (HRT) of 6 h. Treatment at an HRT of 4 h resulted in an effluent TOC concentration of 11 to 15 mg/l. The concentration of suspended solids in the effluent could be reduced to 20 mg/l, which corresponded to 7% of that of the influent. The effluent from both reactors was then treated anaerobically in a fixed-bed reactor system. The TOC concentration and optical density (OD) of the effluent from the aerobic treatment were reduced to 5 mg/l and 0.005, respectively, at an HRT of 2 h. When anaerobically or aerobically treated effluent was passed over an activated carbon column, the effluent TOC concentration was reduced to 2 to 3 mg/l. The conductivity of 1.3 mS/cm in raw wastewater, which was not removed through the above treatments, was reduced to 0.001 mS/cm on an ion-exchange resin column. An effluent quality corresponding to that of ultra-pure water for industrial use was finally attained by the treatment in this multi-step system.     

Induction of flowering ofImpatiens balsamina treated with gibberellic acid and resorcinol

Under strictly non-inductive photoperiods (24-h photoperiods) floral buds were initiated on plants receiving 25 treatments with Reso (resorcinol) or 8 treatments with GA₃ (gibberellic acid) or GA₃ + Reso, while water treated control plants did not flower at all. Although a single treatment of plants with GA₃ or GA₃ + Reso is not adequate to cause induction under LD conditions, its effect is added to the sub-threshold induction caused by one SD (short day: 8-h photoperiod) cycle. The initiation of floral buds was hastened with an increasing number of SD cycles accompanying respective number of treatments, the effect of GA₃ alone or together with Reso being more pronounced than that of Reso alone. GA₃ increased the number of floral buds more than Reso, the number being the highest in plants receiving the respective number of treatments with the combination GA₃ + Reso under both inductive as well as non-inductive photoperiods. Deceased.     

Structure-activity relationship of polyphenols on inhibition of chemical mediator release from rat peritoneal exudate cells

Summary The effect of phenolic compounds in foodstuffs on histamine and leukotriene B₄ (LTB₄) release from rat peritoneal exudate cells and their antioxidative activity were examined to assess their antiallergenic activities. Among them, triphenols such as pyrogallol and gallic acid inhibited histamine release from the cells, but diphenols did not. On the other hand, o- and p-diphenols such as catechol and hydroquinone with strong antioxidative activity inhibited LTB₄ release as strongly as pyrogallol, but an m-derivative resorcinol with weak antioxidative activity did not. Though carboxylated compounds and their noncarboxylated counterparts were antioxidative, the former exerted a much weaker inhibitory effect on the LTB₄ release than the latter. In flavonols, only myricetin with a triphenolic B ring strongly inhibited histamine release, but all flavonols strongly suppressed LTB₄ release irrespective of the number of OH groups in the B ring. Among flavonoids with an o-diphenolic B ring, flavonol and flavone with a C₄-carbonyl group strongly inhibited LTB₄ release, whereas the activity of anthocyan without C₄-carbonyl was much weaker than the above compounds. These results suggest that triphenolic structure is essential for the inhibition of histamine release. On the other hand, antioxidative activity and membrane permeability of phenolic compounds seemed to be essential for the inhibition of LTB₄ release. In addition, the C₄-carbonyl group seemed to be important for strongly inhibiting LTB₄ release.     

Laboratory simulations of the pyrolytic release experiments: An interim report

Summary During its operation on Mars the pyrolytic release experiment (PR) detected the fixation of small amounts of CO₂ and/or CO. Laboratory simulations of the experimental conditions were made in an attempt to substantiate the previous conclusion that these reactions were chemical rather than biological. The selection of model substrata for these tests was based on the known properties of the Martian surface material. After pretreatment and incubation under various conditions, pyrolytic analysis was used to indicate the extent of surface catalyzed conversion of¹⁴CO₂ or¹⁴CO to¹⁴C-organic compounds. This abiotic synthesis was detected in experiments with three iron oxides, viz. hematite, magnetite and maghemite. When the incubation atmosphere was supplemented with water vapor, the levels of synthesis were in a range comparable to that detected in the Viking PR tests. An abiotic synthesis was also detected in experiments with a mixture of clays and minerals (Mars analog soil) or with montmorillonite artifically enriched in iron. With either substratum the reaction appeared to be the result of a photocatalytic synthesis of¹⁴C-organics from¹⁴CO and surface hydroxyl groups. This process was not dependent on the presence of water vapor in the incubation atmosphere. Although a duplication of the Viking data has not been achieved, these findings support the abiotic interpretation of the PR results.     

Synthesis, characterization, thermal behavior, and DNA-cleaving studies of cyano-bridged nickel(II)-copper(II) complexes of 4-(pyridin-2-ylazenyl)resorcinol

We present here the syntheses of a mononuclear Cu^II complex and two polynuclear Cu^II Ni^II complexes of the azenyl ligand, 4‐(pyridin‐2‐ylazenyl)resorcinol (HL; 1). The reaction of HL ( 1 ) and copper(II) perchlorate with KCN gave a mononuclear complex [CuL(CN)] ( 4 ). Using 4 , one pentanuclear complex, [{CuL(NC)}₄Ni](ClO₄)₂ ( 5 ) and one trinuclear complex, [{CuL(CN)}₂NiL]ClO₄ ( 6 ), were prepared and characterized by elemental analyses, magnetic susceptibility, molar conductance, IR, and thermal analysis. Stoichiometric and spectral results of the mononuclear Cu^II complex indicated that the metal/ligand/CN ratio was 1 : 1 : 1, and the ligand behaved as a tridentate ligand forming neutral metal chelates through the pyridinyl and azenyl N‐, and resorcinol O‐atom. The interaction between the compounds (the ligand 1 , its Ni^II and Cu^II complexes without CN, i.e., 2 and 3 , and its complexes with CN, 4 – 6 ) and DNA has also been investigated by agarose gel electrophoresis. The pentanuclear Cu₄Ni complex ( 5 ) with H₂O₂ as a co‐oxidant exhibited the strongest DNA‐cleaving activity.