Search

This paper reports the performance of alizarin based SnO2 dye-sensitized solar cells. A novel template assisted method has been applied for the preparation of tin oxide nanoparticles. For the first time, onion (Allium cepa) was used as a template for the synthesis of tin oxide nanostructures at different pH values. Tin oxide nanostructures were used for the photoanode preparation. A sandwich cell was prepared by using the dye soaked SnO2 film as a photoanode and platinum as a counter electrode. The structural, morphological and optical properties of the nanoparticles were studied using powder X-ray diffraction (XRD), Scanning Electron microscope (SEM), Photoluminescence (PL), Attenuated Total Reflectance (ATR) spectra and UV-visible spectroscopic techniques. Current-voltage (I-V) characteristics have been measured using electrochemical workstation under the presence of solar illumination. Characteristic parameters of the fabricated cell were determined on the basis of the measured I-V curves.

The present communication aims to obtain a novel Ce3+/TiO2 thin film in a single step facile method using the in situ template process. The material was characterized by the XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), TEM (transmission electron microscope), and AFM (atomic force microscope) analyses. The thin film catalyst was intended to introduce in the degradation of one of potential dye Alizarin Yellow from aqueous solutions using the UV-A radiations. The mechanisms of degradation along with the physicochemical parametric studies were conducted extensively. The mineralization of pollutant and the replicate use of catalysts further enhance the applicability of present communication. Additionally, the real matrix treatment was conducted to simulate the treatment process.

The harmful and destructive effects of excessive consumption of thiourea in various industries and agriculture have caused health and environmental concerns. Hence, attention has been paid to the need for analysis and detection thiourea at very low concentrations. The aim of this study was to determine the efficiency of electrochemical sensor based on glass carbon electrode modified with Ag nanoparticles and alizarin yellow to detect thiourea as a pollutant. Glass carbon electrode was first modified by alizarin yellow polymer and Ag nanoparticles through electropolymerization and chronoamperometry methods, respectively. The characteristics of the modified electrode were determined through FESEM and EDAX analysis and thiourea concentration was measured through cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods. The results showed that the linear range, limit of detection, and sensitivity were 10 to 940 µM, 3.3 µM and 0.181 µA/µM, respectively. The stability and reproducibility of the sensor response as well as the interference effect of some anion species were investigated on the performance of the sensor in determining thiourea. The results indicate the optimum stability and reproducibility and no interference effect of the studied species on efficiency of the sensor in determining thiourea.

The consumption of noni fruits has been linked to several health benefits, many of which are attributed to scopoletin, alizarin and rutin that are present in the fruits. However, there is no report on optimized high hydrostatic pressure (HHP) extraction of noni fruits. In this study, the effects of ethanol concentration, pressure and time were evaluated individually on the extraction yields of bioactive compounds from noni fruits. The optimum extraction condition was then investigated to maximize the yields using response surface methodology with a Box-Behnken Design. The extraction pressure and ethanol concentration were the most statistically significant variables in obtaining high extraction yields. The optimal HHP extraction condition at the highest desirability (> 0.998) for simultaneous extraction of scopoletin, alizarin and rutin was as follows: pressure 544 MPa, time 15 min and ethanol concentration 65%, which gave the maximum yields of 82.4, 77.2 and 82.2% for scopoletin, alizarin and rutin, respectively. All bioactive compounds showed the positive linear and negative quadratic effects of pressure, the negative linear and negative quadratic effects of ethanol concentration, and the negative interaction effect between pressure and ethanol concentration on extraction yields. This study highlights the applicability of HHP in extracting bioactive compounds from noni fruits, taking advantage of high yield, extraction time saving and reduced solvent volume at room temperature.

A kind of smart calcium alginate fiber having pH indicating properties was proposed to monitor wound healing. The smart calcium alginate fiber was prepared by dyeing the hydroxypropyl trimethyl ammonium chloride chitosan (HACC) modified calcium alginate fiber with alizarin dye and anthocyanin dye, respectively. It was worth noting that modification of calcium alginate fibers with HACC enhanced the dyeing and antibacterial properties, simultaneously. When the concentration of HACC was 10 g/L, the modified calcium alginate fiber had the best dyeing performance. At the same time, the dyeing process had no significant influence on the mechanical properties of the fibers with the strength loss only around 0.2 cN/dtex. The smart calcium alginate fibers exhibited a rapid and significant color change and reversible color response at pH 2–11. Moreover, the color change could be easily observed by naked eye. Therefore, the prepared calcium alginate fibers could be a good candidate for intelligent wound dressings for visual monitoring of wound healing.

Microwave radiation was used for synthesis of an adsorbent using rice husk. The activation of the rice husk sample was performed by H3PO4 and 6 min of the microwave radiation with power 700 W. The synthesized adsorbent was characterized by SEM, FT-IR, BET and XRD techniques. These analyses showed the prepared adsorbent is an amorphous and mesoporous nano-adsorbent with BET surface area 276.43 m2/g. It has some aromatic groups and O-H, C-C, C-O and C-O bands in its structure. Adsorption of alizarin yellow on the synthesized nano-adsorbent was investigated and the influences of adsorbent dosage (0.1–2g/L) and temperature (25–40 ·C) on dye removal from aqueous solution were investigated. The kinetic, equilibrium and thermodynamics studies of alizarin yellow removal from aqueous solution using the prepared adsorbent were carried out. The adsorption performance of alizarin yellow on the prepared adsorbent was compared with a commercial activated carbon. The importance of this study is in providing a condition for preparation of a low cost adsorbent with high adsorption capacity (712.63 mg/g) for alizarin yellow. The comparison of adsorption capacities of the prepared adsorbent from rice husk and other adsorbents proved it is a perfect adsorbent.

Polymer metal oxide composites find numerous applications for the decontamination of various pollutants. In the present study, chitosan conjugated tin magnetic nanocomposites (Sn-CCMN) was synthesized via a modified co-precipitation method. The synthesized material was characterized using FT-IR, XRD, SEM and EDX spectroscopic techniques. The FT-IR data confirmed the successful synthesis of the material, whereas the XRD analysis showed the amorphous nature of Sn-CCMN. The SEM results declared the irregular shape with porous surfaces and almost uniform particle size of Sn-CMMN with an average grain size of 84 ± 3 nm and desired elemental composition as confirm from the EXD spectral data. It was concluded that the Sn–Fe magnetic nanoparticles were well-embedded in the chitosan polymer matrix. The band gap energy (Eg) and point of zero charge (PZC) of the synthesized material were also determined and found to be 3.16 eV and 7.75, respectively. The photocatalytic potential of the synthesized Sn-CCMN was investigated under UV-light irradiation (254 nm and 15 W) in the aqueous medium using alizarin yellow (ALY) as a model environmental pollutant. The effect of various operating parameters such as irradiation time, pH, catalyst dose and concentration of dye was studied and at the optimal conditions, Sn-CCMN was applied for the photocatalytic degradation of ALY in the real samples. The synthesized material showed excellent photocatalytic property with reaction rate constant (k) and rate of reaction of 0.0039 min−1 and 0.042 ppm/min, respectively. The synthesized Sn-CCMN was recycled and reused, maintaining its structural characteristics and excellent photocatalytic activity for four consecutive batches.

The supercritical carbon dioxide (SC-CO2) dyeing technology is a green dyeing technology, and the usage of natural dye makes SC-CO2 dyeing technology safer and more environment-friendly. Nevertheless, after using natural dye in SC-CO2 dyeing, the color depth and fastness of dyed natural fabric are poor. In this study, alkyl and hydroxyalkyl groups were grafted onto alizarin, which is a natural dye, to elevate the color depths and fastness of alizarin-derivative-dyed natural fabric. The results demonstrate that the color depths of alkyl-alizarin-dyed and hydroxyalkyl-alizarin-dyed natural fabrics were increased. This has to do with the increase in the solubilities of alkyl alizarin and hydroxyalkyl alizarin in SC-CO2. The hydroxybutyl-alizarin-dyed wool displayed the best color depth (K/S value: 6.44). And the hydroxyalkyl-alizarin-dyed natural fabric showed good washing fastness and rubbing fastness (about 4–5 level), because that hydroxyalkyl alizarin could be linked by a covalent bond to the natural fabric.

High-performance liquid chromatography coupled to a diode-array detector (HPLC-DAD) is used to investigate 30 samples which were removed from 27 ancient Egyptian fabrics of the Fill-Trevisiol collection. Attention is focused in this paper on fabrics of the Roman and Byzantine periods, with red and deep violet–blue wool weft threads which are Z-spun. The following dyes are identified in fabrics which date to the Roman period (first–fifth c. ad): mollusc purple, madder, and indigo/woad (Indigofera species and other, Isatis tinctoria L.). The results for the Byzantine (fifth–seventh c. ad) fabrics are richer in terms of identified dyes: apart from the three aforementioned dyes, the use of kermes (Kermes vermilio Planchon) and cochineal is revealed as the two coccid dyes have been detected in six Egyptian–Byzantine fabrics. Moreover, a yellow dye (probably Reseda luteola L.) is identified in one sample. Finally, samples taken from two fabrics, which date to the Islamic period, were dyed using indigo/woad and lac (Kerria lacca, Kerr). Mixing madder and indigo/woad to imitate true purple was a common practice in ancient Egypt and this is confirmed by the HPLC results in several samples. Semi-quantitative results are obtained from the HPLC peak areas and lead to the following conclusions. Madder dyes which were rich or poor in alizarin, compared to purpurin, and could have been therefore obtained from Rubia tinctorum L. and Rubia peregrina L., respectively are detected in Byzantine fabrics. Only alizarin-rich madder dyes are identified in some samples from Roman fabrics, but in some other samples the relative alizarin-to-purpurin ratio cannot be measured with confidence. Cochineal is found in two samples. The biological source of cochineal (Porphyrophora hamelii Brandt) is possible to be chemically identified only in one sample. The HPLC results of the molluscan dye detected in a Roman fabric are compared with the relative compositions of extracts of the three Mediterranean molluscs leading to the speculation that the Roman purple sample was probably dyed using Hexaplex trunculus L. The molluscan dye was furthermore detected in a Byzantine sample where it was combined with madder. Finally, it is reported that the standard (hydrochloric) acid hydrolysis method which is commonly applied to extract dyes from archaeological samples does not have any noticeable effect on the relative composition of the molluscan dye.

Rubia cordifolia L., is an industrially viable medicinal crop and is widely exploited for the therapeutic potential of its bioactive metabolite, purpurin. The present investigation aimed to explore the chemotypic and molecular variability in seven wild populations of R. cordifolia from South Eastern Ghats region of India. Thirty-eight individuals were assessed for molecular fingerprinting (ISSR markers) and densitometric quantification of purpurin and alizarin. The populations of Yelagiri Hills and Shervaroy Hills contained the highest levels of alizarin (0.115 and 0.093%, respectively) while Pachamalai and Kolli Hills revealed the highest purpurin content (0.284 and 0.280%, respectively). Genetic diversity was generally higher in the same populations that produced higher metabolite content, with the exception of Pachamalai, suggesting a highly prioritized conservation concern. The study revealed a Nei's total gene diversity at species level of 0.266 and of 0.187 at population level, with an average population genetic differentiation of 0.28. No clear genetic or chemical structure was retrieved between the studied populations, with individuals from different locations clustering together, and no significant correlation was obtained between metabolites and genetic diversity or between these and the populations' geographic distances.

Photocatalytic degradation of pollutants based on semiconductor quantum dots (QDs) can be applied in wastewater purification methods. However, application of free QDs was associated with some difficulties, such as oxidation and agglomeration of QDs and difficulties in separation. As a solution to these problems, we have proposed the production of mesoporous SBA-15 supported CdS quantum dots as a more stable photo-catalyst. The efficiency of these prepared nanocomposites was examined for photocatalytic degradation of Alizarin, as an organic pollutant. Results demonstrated that the proposed material is a promising catalyst for photocatalytic degradation of dyes in wastewaters. The kinetic and adsorption isotherms of photocatalytic degradation process were also studied and a detailed mechanism proposed for degradation process. The proposed mechanism was studied using free radicals trapping experiments; results demonstrated that the $${}^{ \bullet }{\text{O}}_{2}^{ - }$$ radicals are active intermediates and have an important role in the photodegradation mechanism.

A halochromic sensor of cellulose acetate nanofibres and alizarin as a fish spoilage indicator in real time is described. The colour of this on-packaging sensor changes visually with an increase in the amount of total volatile basic nitrogen (TVB-N) and a rise in the pH value of product. Rainbow trout fillets were kept at refrigerator temperature (4 °C) for 12 days. TVB-N, pH, total viable count (TVC) and colourimetric tests were performed. Results showed that the pH, the TVB-N and the TVC increased with time. No colour changes were observed within 48 h, but after the fourth day, a very light brick colour on the nanosensor was observed. This colour became darker on the sixth day, representing actual pH changes. The colour of sensor tended towards violet on the 12th day; the colourimetric result proved the expected visual colour change in the electrospun nanosensor due to alizarin usage as a halochromic dye.

An adsorbent formed from MCM-41 and layered double hydroxides (LDH) coated on magnetic nanoparticles was synthesized and modified with a cationic surfactant (Fe3O4@MCM@Cu–Fe–LDH) for use in dispersive micro solid-phase extraction for removal of Alizarin Yellow (AY) (an anionic dye) prior to high-performance liquid chromatography–ultraviolet (HPLC–UV) detection. This adsorbent was obtained from mesopore MCM-41 coated with Fe3O4 as main core and Cu–Fe–layered double hydroxide (Cu–Fe–LDH) as nanoplatelet shell. The adsorbent was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analyses. Also, the surface morphology, Brunauer–Emmett–Teller (BET) specific surface area, and Barrett–Joyner–Halenda (BJH) pore size of the adsorbent were obtained. The adsorption isotherms were studied based on the Langmuir and Freundlich models. Adsorption data were successfully fit using the Langmuir model, showing maximum adsorption capacity of 121.95 mg g−1. The proposed method showed good linearity for AY with correlation coefficient R2 > 0.9998. The limit of detection was 0.5 µg L−1. Precision of 6.5% was obtained, as relative standard deviation (RSD) (n = 6). The method was successfully applied to determine AY in well and wastewater samples.

To dye poly(lactic acid) (PLA) fiber with natural dyes has gained importance in recent years due to the production of the fully eco-friendly textile products. In this study, pure and modified PLA fibers with two different POSS nanoparticles, namely N-phenyl aminopropyl POSS (AP-POSS) and octa (aminophenyl) polyhedral oligomeric silsesquioxane (OAPPOSS), are dyed with three different natural dyes including alizarin, lawsone and indigo. The effects of the dyeing conditions including dyeing temperature and time, POSS nanoparticle concentration, natural dye types and concentrations are investigated on the dyeability properties of the PLA fiber samples. The wash and light fastness of the fiber samples are also investigated. According to the dyeability results, it is concluded that POSS nanoparticles are effective for increasing the dyeability of the PLA fiber with all natural dyes used in this study. As the added amount of the POSS nanoparticle increases, the dyeability of the PLA fiber increases. When the performances of the POSS nanoparticles are compared, it is seen that OAP-POSS is more effective than the AP-POSS nanoparticle.

Electrochemical polymerization of alizarin on glassy carbon electrode (GCE) was carried out in acidic solution by cyclic voltammetry (CV), and the polymerization process was monitored by electrochemical quartz crystal microbalance (EQCM). A possible mechanism concerning the polymerization of alizarin was also proposed in this work. The as-synthesized poly(alizarin) was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The study on electrode reaction process shows that the electrode reaction of poly(alizarin) is controlled by diffusion. Finally, the activation energy (E a) of the electrode reactions of poly(alizarin) was obtained according to the temperature dependence of the redox peak currents.

This research has been conducted to study extraction of an anionic dye, Alizarin Red S (ARS), from the aqueous phase into the organic phase in a T-junction microchannel. The organic phase included Aliquat 336 and 1-octanol. Equal volumetric flow rates of aqueous and organic phases were adjusted in all the experiments. Designing the experiments and analyzing of the parameters that affect the extraction percentage of ARS were carried out using response surface methodology. The parameters were feed pH, feed concentration, extractant concentration and flow rate of aqueous and organic phases. The maximum extraction percentage of 98.7 was obtained at the feed pH of 3, feed concentration of 5000 mg L−1, extractant concentration of 4 vol.% and flow rate of 2.5 mL min−1. Under the optimum conditions obtained from the experimental design analysis, ARS extraction was performed in a batch system, too. The two-phase contact times to reach the extraction percentage of 98.7 in the microchannel and batch system were 2.4 s and 5.5 min, respectively.

Series of novel alizarin and phosphoryl amino acid scaffold (4a–4d, 8a–8d) were synthesized and evaluated for the suppression of cancer cell proliferation in vitro against MGC-803, HepG2, T24, NCI-H460, and SK-OV-3 cell lines by standard 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay compared with commercial anticancer drug doxorubicin. Interestingly, all newly synthesized compounds exhibited relatively high cytotoxicity compared with alizarin and low cytotoxicity against human normal liver cell line HL-7702 cells. Especially, compound 8d showed the best cytotoxicity against SK-OV-3 cells with IC50 7.09 µM, which was slightly worse than that of drug doxorubicin. The cell apoptosis-inducing activity of representative compound 8d in SK-OV-3 cells revealed that the anticancer activity of this compound depended on apoptosis of cancer cells via regulation of Bcl-2 family members, activation of caspase-9 and caspase-3. Cell cycle analysis confirmed that compound 8d mainly arrested SK-OV-3 cells in G2 stage. In addition, molecular docking studies were performed to position compound 8d into the telomerase (5CQG) active site to determine the probable binding model.

Two new Co(II) complexes of 4-((3-ethoxy-2-hydroxybenzylidene)amino)-N-(thiazol-2-yl)benzenesulphonamide and 4-((pyridin-2-ylmethylene)amino)-N-(thiazol-2-yl)benzene sulfonamide were synthesised. The structure of the complexes was identified by elemental analysis, FT-IR, electronic, EI mass, Powder XRD spectra and magnetic moment. The TG and DTA patterns of the complexes were supported the structures. The fluorescence quenching of these complexes with alizarin dye were premeditated and the free energy change (∆Get) for electron transfer process was designed by Rehm-Weller equation. The [Co(L1-H)2(H2O)2] and [Co(L2)2(H2O)2].2H2O were submitted for in vitro cytotoxicity studies in human breast cancer cell line (MCF 7).

The study and characterization of old artifacts such as pigments requires the use of techniques that need a small amount of sample to perform the analysis because of the high value of these samples. In recent years, organic molecules such as anthraquinone dyes have been identified by surface-enhanced Raman spectroscopy (SERS). However, different sample treatments must be applied to isolate the organic dye from the mordant, which produces great fluorescence in the Raman measurements. In this work, optimization of sample treatment for the SERS analysis of anthraquinone dyes was performed. Sample mass, the organic solvent, and its volume were optimized and different slide materials and excitation lasers were compared to choose the best conditions for the identification of the dyes. The optimization of sample treatment resulted in 5 mg of sample as the optimum amount. Further, two consecutive extractions with 0.5 mL of ethyl acetate was the best option for the extraction of the dye. A quartz slide was used instead of a glass slide to reduce background signal, and an excitation laser of 532 nm offers better results than one of 785 nm. The optimized method was applied to the characterization of the dyes used in Pompeian pink and purple lake pigments. Alizarin and purpurin anthraquinone dyes, obtained from madder lake, were identified as the organic colorants. The SERS results were confirmed by those obtained by means of UV-visible spectroscopy. Graphical Abstract ᅟ.

The aim of this study was to evaluate the biosorption capacity of selected strains of microscopic fungi. We optimized the biosorption process and used the Freundlich isotherm for three strains: H. haematococca BwIII43, K37 and T. harzianum BsIII33 to describe the biosorption equilibrium of anthraquinone dye, Alizarin Blue Black B (ABBB) and alkali lignin (AL). In optimal conditions (1 g of mycelium biomass, pH = 7.0, 28 °C) for ABBB and AL sorption, the live biomass of H. haematococca BwIII43 was characterized by a higher sorption capacity, amounting to 247.47 and 161.00 mg g−1, respectively. The highest sorption properties toward anthraquinone dye (K F = 19.96 mg g−1) were shown for the biomass of H. haematococca K37. In the presence of alkali lignin, the highest sorption capacity and bond strength exhibited the biomass of H. haematococca BwIII43 (K F = 28.20 mg g−1, n = 3.46). Effective decolorization of ABBB and AL by the selected strains of microscopic fungi indicated that the biosorption process additionally enhanced the removal of color compounds from the solution.

Reactions of the cycloaurated gold(III) dichloride complexes [AuCl2(anp)] (anp = 2-anilinopyridyl), [AuCl2(bp)] (bp = 2-benzylpyridyl) and [AuCl2(tolpy)] (tolpy = 2-(p-tolyl)pyridyl) with alizarin (H2az) and Me3N base in refluxing methanol gave the complexes [Au(az)L] (L = anp, bp or tolpy). Additionally, the reaction of [AuCl2(tolpy)] with 3,4-dihydroxybenzaldehyde (H2dhb) and Me3N gave the complex [Au(dhb)(tolpy)]. These complexes contain the ligands coordinated as functionalised catecholate groups, allowing introduction of new functionalities into this class of complex. The complexes are poorly soluble in most organic solvents but were successfully characterised by ESI MS, IR and NMR spectroscopies. A detailed 1H and 13C NMR study on [Au(dhb)(tolpy)] shows that it exists as two isomers with regard to the position of the aldehyde group compared to the cycloaurated ring system; DFT calculations were carried out in order to provide some insight on the spectroscopic assignment of the two isomers.

The optical and electrical properties of two dyes purpurin (1,2,4-trihydroxy-9, 10-anthracenedione) and alizarin complexone (alizarin-3-methylimino-N,N-diacetic acid) as sensitizers for dye-sensitized solar cells were investigated by using UV–Vis spectrum, FT-IR spectrum, cyclic voltammetry and I–V (current–voltage) characteristics. In addition, electrochemical impedance spectroscopy was adopted to research the electrons transfer process between each interface of the dye-sensitized solar cell. For comparison with the experiments, the frontier molecular orbitals, vibration analysis, the total static first hyperpolarizability and driving force of electron injection were calculated by using density functional theory (DFT) with B3LYP, at 6-31G(d) basis set. Moreover, the transition properties were investigated by using time-dependent density functional theory (TD-DFT) with PBEPBE functional at 6-311+G(d,p) basis set in theory. The solvent effect and basis set effect were taken into consideration to investigate the excited state properties of the dyes. The results showed that alizarin complexone had a higher energy conversion efficiency of 0.27 % than that of purpurin (0.13 %), with higher open circuit voltage ( $$V_{oc}$$ ) of 0.45 V, higher short circuit current density ( $$I_{sc}$$ ) of 0.89 mA cm−2 and higher fill factor ( $${\text{ff}}$$ ) of 0.67, indicating that the photovoltaic characteristics of alizarin excelled that of purpurin.

The reactive intermediates generated by the addition of isocyanides to dialkyl acetylenedicarboxylates were trapped by alizarin to produce dialkyl 2-alkyl (aryl) amino-6,11-dihydro-12-hydroxy-6,11-dioxo-4H-naphtho [2,3-g]chromene-3,4-dicarboxylates in good yields. When the reactions were carried out in the presence of ethyl propiolate as acetylenic component, ethyl 4-alkyl (aryl) imino-4-(9,10-dihydro-1-hydroxy-9,10-dioxoanthracen-2-yloxy)but-2-enoates were obtained.

Agarose gel (agargel) composites with commercial and laboratory made silver nanoparticles were prepared by a wet solution method at room temperature. The gel composites were used for pigment extraction and detection by Raman spectroscopy. Red (alizarin) and violet (crystal violet) pigments deposited on paper were extracted by the composites and were investigated by micro-Raman spectroscopy. Evaluation was carried out of the surface-enhanced Raman spectroscopy (SERS) effect induced by the silver nanoparticles embedded in the gel. A kinetic approach as a function of time was used to determine the efficiency of pigments extraction by composites deposition. A non-invasive extraction process of few minutes is demonstrated. This process induces active SERS for both used pigments. The reported results show the full exploitability of agargel silver nanoparticle composites for the extraction of pigments from paper based artworks.

A gravimetric method is used to study corrosive wear of a test specimen – counterbody pair made of steel 40X in running water with pH 7.6 containing (g/liter): Ca2+ 0.035, Mg2+ 0.016, Cl– 0.023, SO 4 2 – 0.039, with addition of alizarin oil (AO). It is established that AO in running water reduces the amount of corrosive wear in the load range 4.8–20.2 kg, and as load increases the protective effect of AO decreases from 52.4 to 1%.

The antimicrobial activities of materials derived from Cassia obtusifolia seeds were evaluated against the seven food-borne bacteria. The active constituent of C. obtusifolia seeds was isolated using various chromatographic techniques and characterized as 1,2-dihydroxyanthraquinone (alizarin). The purified alizarin exhibited weak activity against Bacillus cereus (clean zone diameter, 11.0 mm), and moderate activity against Staphylococcus epidermidis (17.5 mm) and Salmonella enterica (16.2 mm) at 2.0 mg/disc. When compared with alizarin analogues, alizarin-3-methyliminodiacetic acid exhibited the strongest antimicrobial activity against B. cereus, S. intermedius, S. epidermidis, and S. enterica at 2.0 mg/disc, whereas the other analogues exhibited no antimicrobial activity against the seven food-borne bacteria. Taken together, these results indicate that alizarin isolated from C. obtusifolia seeds and its structural analogues may be useful as natural preservatives.

Morinda citrifolia L. belongs to family Rubiaceae. It is a traditional Polynesian medicinal plant. Its root serves as a rich source of various anthraquinone constituents. The anthraquinone compounds exhibit therapeutic effects of antibacterial, antiviral and anticancer activities. In the present work, an adventitious root culture of M. citrifolia was established and the effectiveness of various elicitors viz, yeast extract, xylan, pectin and the precursor α-ketoglutaric acid on the level of anthraquinone production in adventitious root cultures were assayed. Adventitious root proliferation was achieved in Murashige and Skoog liquid medium supplemented with 24 μM Indole-3-butyric acid. The anthraquinone content was determined by spectrophotometric analysis and the anthraquinone constituents–viz, alizarin and purpurin were quantified by high-performance liquid chromatographic method. Enhancement in alizarin and purpurin along with total anthraquinones was detected due to the addition of precursor and elicitors. Pectin (20 mg/l) added cultures resulted in highest anthraquinone accumulation (44.4 mg/g dw). The protocol developed for the regeneration of roots was simple, reproducible and reliable for the possible commercial production of in vitro root biomass based alizarin and purpurin.

The photocatalytic oxidative degradation and discoloration of the reactive dye was investigated. Along with photochemical oxidation process, the sonochemical effect was also used. Experiments were performed in slurry mode in both UV and solar light at optimized conditions. Degradation observed was 88% under photocatalytic optimized conditions, i.e., pH 4.8, TiO2 = 0.3 g L−1 and oxidant dose of 0.3 g L−1 after 180 min. sonophotocatalytic treatment enhanced the degradation up to 94% with optimized parameters of photocatalytic treatment. The results obtained were quite appreciable as also confirmed from reduction in COD from 280 to 36 mg L−1. The results of sonophotocatalytic degradation of dye showed that it could be used as efficient and environmental friendly technique for the complete degradation of recalcitrant organic pollutants that will increase the chances for the reuse of wastewater.

Series of novel hybrids of alizarin and diamide scaffold (3a–3h, 7a–7h) were designed and synthesized. In vitro antitumor activities of all compounds against HepG-2, CNE, Spca-2, Hct-116, and MGC-803 cell lines were evaluated, and employing standard MTT assay compared with commercial anticancer drug 5-fluorouracil (5-FU). Compounds 7b, 7c, 7d, and 7e showed relatively high cytotoxicity. Especially, compound 7c exhibited the best cytotoxicity against CNE cells with IC50 9.08 µM, which was even stronger than that of 5-FU. All the synthesized compounds exhibited low cytotoxicity against HUVEC cells. The action mechanism of representative compound 7c was preliminarily investigated by flow cytometry, which indicated that the compound can induce cell apoptosis in CNE cells. Cell cycle analysis showed that compound 7c mainly arrested CNE cells in G1 stage. In addition, the binding properties of a model analog 7c to DNA were investigated by different methods (fluorescence, CD spectroscopy), and the results indicated that 7c showed a moderate preference for binding ct-DNA.

Eleven new 2-O-side-chain derivatives of alizarin were synthesized via esterification, substitution, hydrolysis, or elimination reactions. The structures of all the products were confirmed by 1H NMR, MS, and elemental analysis. Compared with alizarin, most of the derivatives had significantly higher DNA binding affinity based on interaction with ct-DNA. In particular, compound 8 exhibited the best cytotoxicity against HeLa cells with IC50 20 μM and could induce HeLa cells apoptosis.

Alizarin-series dyes (alizarin, alizarin red S, alizarin yellow GG, or mordant orange) are grafted onto shape memory polyurethane (PU) through an allophanate bonding, and the photoluminescence and the low-temperature flexibility of the resulting PUs are tested. The PU is mainly composed of 4,4′-methylenebis(phenylisocyanate) (MDI), poly (tetramethyleneglycol) (PTMG), and 1,4-butanediol (BD), and the dye is connected, through another MDI, to the carbamate moiety of the PU chain. The PUs with different dye contents are characterized, and their shape recovery and photoluminescence properties are compared. With respect to the tensile mechanical properties, the maximum stress increases up to 50 MPa, and the strain remains above 1000 % even after the dye is grafted onto the PU. The shape recovery is as high as 99 %, and the shape retention improves as the dye content increases. Finally, the photoluminescence of the PUs is demonstrated by the luminescent light emission test, and the dye-grafted PU shows excellent low-temperature flexibility compared with that of linear PU.

The adsorption processes of alizarin onto hydrophilic carbon nanoparticles (Emperor 2000™) are investigated. The significant increase in voltammetric responses for pre-adsorbed alizarin compared with those for solution confirms high affinity of alizarin to carbon nanoparticles (possibly due to π–π stacking interaction between aromatic rings of alizarin and surface-sulfonated carbon nanoparticles). To obtain the optimum of adsorption conditions, the effects of pH, agitation rate, and adsorption time are investigated. Under square wave voltammetry conditions, the peak current for the reduction of alizarin shows a linear relationship with concentration in the range from 2.0 to 10.0 nM. The limit of detection is estimated 5.8 × 10−9 mol L−1. Next, alizarin is applied as a receptor for sensing of trace vanadium in acetate buffer pH 5. Linear calibration curves are obtained for vanadium in the range of 1.0 × 10−6 to 1.0 × 10−4 mol L−1 and the limit of detection is estimated 9.6 × 10−8 mol L−1. Determination of vanadium in real samples such as sea and tap water is demonstrated.

Anthraquinones consist of several hundreds of derivatives that differ in the nature and positions of substituent groups which are known to have several biological activities including antitumor properties. Interaction of molecules with DNA persists to be an extremely vital parameter while endeavouring to formulate therapeutics. In this study, few anthraquinone derivatives such as 1,2-dihydroxyanthraquinone (alizarin), 1,4-dihydroxyanthraquinone (quinizarin), 1,8-dihydroxyanthraquinone (danthron), 1,2,4-trihydroxyanthraquinone (purpurin), 1,4-diaminoanthraquinone, and 1-methylaminoanthraquinone were analyzed for its possible interaction with calf-thymus DNA through spectroscopy and in silico analysis. Our UV spectroscopic results indicate that all selected anthraquinones interact with DNA probably by external binding. Molar extinction coefficient has been calculated for chosen six anthraquinones. FT-IR results suggest that significant shifts of peaks as well as disappearance of certain characteristic peaks were indicators of the plausible interaction going on due to dye-DNA adduct formation. Among the six dyes used, purpurin showed better results and indicates the relatively strong binding affinity with DNA. Our molecular modeling results also show that purpurin has comparatively higher DNA interaction with a score of -6.18 compared with the ethidium bromide of -5.02 and intercalate the DNA.

In this study microwave assisted technique has been adopted for the synthesis of different weight ratios of TiO2 dispersed on Santa barbara amorphous-15 (SBA-15) support. Morphological study revealed TiO2 particles (4–10 nm) uniformly distributed on SBA-15 while increases in SBA-15 content results in higher specific surface area (524–237 m2/g). The diffraction intensity of 101 plane of anatase polymorph was seen increasing with increase in TiO2 ratio. All the photocatalysts were having a mesoporous nature and follow the Langmuir IV isotherm, SBA-15 posses the highest pore volume (0.93 cm3 g−1) which consistently decreased with TiO2 content and was lowest (0.50 cm3 g−1) in case of 5 wt% of TiO2 followed by P25 (0.45 cm3 g−1) while pore diameter increased after TiO2 incorporation due to pore strain. The photocatalytic activity of the nanocomposites were analysed for the photodegradation of alizarin dye and pentachlorophenol under UV light irradiation. The reaction kinetics suggested the highest efficiency (98 % for alizarin and 94 % for PCP) of 5 wt% TiO2 compared to other photocatalysts, these nanocomposites were reused for several cycles, which is most important for heterogeneous photocatalytic degradation reaction. This study demonstrates the synthesis of silica embedded TiO2 nanocomposites by microwave assisted technique and their catalytic influence on degradation of organic dyes and pollutants. Higher loading of titania (SBA-15/TiO2, 1:5) results better catalytic performance than commercial nano TiO2 (P25).

The anthraquinone components of the roots of various species of madder (Rubia spp.) have been used for millennia as red colorants in textiles, carpets and other objects. Although many species of Rubia are known, only a few of them have been used widely for dyeing. Furthermore, though nearly 70 anthraquinones have been found in Rubia species, only a few of these occur consistently at relatively high levels. Knowledge of the plant dyestuffs is helpful for establishing the location of production, production method and/or history of the dyed object. Using plant material and dyed textile fibers obtained from a number of sources, and HPLC with photodiode array and mass spectrometric detection for analysis, we have been able to identify marker anthraquinones that permit differentiation of the more common species of madder used for dyeing in Eurasia. Textiles dyed with all of the species examined contain varying amounts of purpurin, but only those dyed with Rubia akane contain large amounts of 6-hydroxyrubiadin (1,3,6-trihydroxy-2-methylanthraquinone) or its glycosides. Textiles dyed with R. tinctorum contain primarily alizarin, whereas those dyed with R. cordifolia and R. peregrina contain mostly purpurin, munjistin and pseudopurpurin, but little or no alizarin or 6-hydroxyrubiadin. The latter two species cannot reliably be distinguished from each other, however. The plants themselves often contain glycoside precursors not usually seen in the dyed materials.

The present study is investigating the immobilization of Rubia tinctorum L. suspension cultures. The effects of three inoculation volumes and three immobilization materials (loofa, sisal and jute) on fresh and dry weights of biomass as well as on alizarin and purpurin production were determined in this study. Two grams of four-week old callus tissue were transferred to liquid medium to establish suspension cultures. After four weeks, suspension cultures of R.tinctorum at concentration of 8 × 105 living cells/ml were immobilized with lignocellulosic materials and the cells were attached to all immobilization materials at the end of the first week and started to form aggregates on them. At the fourth week of these batch systems, biomass was measured approximately three times higher than the starting suspension cultures. The highest fresh weight was obtained (339.40 g/l) from sisal with ½ inoculation ratio. Immobilization materials and inoculation volumes had an effect on dry weights, and accordingly, the most effective combinations were jute with ¼ (J3) and ½ (J1) inoculation volumes with 7.86 and 7.82 g/l dry weights, respectively. Alizarin and purpurin contents of immobilized cells, analyzed with U-HPLC method, were 6.05 and 22.91 times higher than inoculated cells. All immobilization materials used in this study had no negative effect on to cells and biomass accumulation was enhanced. Concomitantly with rapid biomass increase, alizarin and purpurin production was ascended.

With the development of the textile industry, there has been a demand for dye removal from contaminated effluents. In recent years, attention has been directed toward various natural solid materials that are capable of removing pollutants from contaminated water at low cost. One such material is sugarcane bagasse. The aim of the present study was to evaluate adsorption of the dye Acid Violet Alizarin N with different concentrations of sugarcane bagasse and granulometry in agitated systems at different pH. The most promising data (achieved with pH 2.5) was analyzed with both Freundlich and Langmuir isotherms equations. The model that better fits dye adsorption interaction into sugarcane bagasse is Freundlich equation, and thus the multilayer model. Moreover, a smaller bagasse granulometry led to greater dye adsorption. The best treatment was achieved with a granulometry value lower than 0.21 mm at pH 2.50, in which the total removal was estimated at a concentration of 16.25 mg mL−1. Hence, sugarcane bagasse proves to be very attractive for dye removal from textile effluents.

In this paper, three anthraquinones (alizarin (1,2-dihydroxy-9,10-anthraquinone), alizarin-DA (1,2-dihydroxy-9,10-anthraquinone-3-aminomethyl-N,N-diacetic acid) and alizarin-DA-Fe (1,2-dihydroxy-9,10-anthraquinone-3-aminomethyl-N,N-diacetate-ferric(III))) with a tricyclic anthraquinone planar structure are used as quenchers, to study their interaction with bovine serum albumin (BSA) molecules by fluorescence spectroscopy. The results show that these three anthraquinones can bind to BSA molecules efficiently but the stabilities decrease in the order alizarin, alizarin-DA and alizarin-DA-Fe. In addition, synchronous fluorescence spectroscopy indicates that the tryptophan (Trp) residues of BSA molecules are more accessible to alizarin and alizarin-DA than the tyrosine (Tyr) residues, but both have similar accessibility to alizarin-DA-Fe.

The 1:1 intermediate generated by the addition of triphenylphosphine to dialkyl acetylenedicarboxylates is trapped by alizarin to produce alkyl 6,11-dihydro-12-hydroxy-2,6,11-trioxo-2H-naphtho[2,3-g]chromene-4-carboxylates in good yields. When ethyl propiolate was used, the reaction afforded ethyl 6,11-dihydro-6,11-dioxoanthra[1,2-d][1,3]-dioxole-2-acetate. The reaction of dialkyl acetylenedicarboxylates, alizarin, and trialkyl phosphites produced dialkyl 2-(dialkoxyphosphoryl)-3-(9,10-dihydro-1-hydroxy-9,10-dioxoanthracen-2-yloxy)succinates.

The binding properties on alizarin to human serum albumin (HSA) have been studied for the first time using fluorescence spectroscopy in combination with UV-visible absorbance spectroscopy. The results showed that alizarin strongly quenched the intrinsic fluorescence of HSA through a static quenching procedure, and non-radiation energy transfer occurred within the molecules. The number of binding sites was 1, and the efficiency of Förster energy transfer provided a distance of 1.83 nm between tryptophan and alizarin binding site. ΔH(θ), ΔS(θ) and ΔG(θ) were obtained based on the quenching constants and thermodynamic theory (ΔH(θ)0, ΔS(θ)0 and ΔG(θ)0). These results indicated that hydrophobic and electrostatic interactions are the main binding forces in the alizarin-HSA system. In addition, the results obtained from synchronous fluorescence spectra and three-dimensional fluorescence spectra showed that the binding of alizarin with HSA could induce conformational changes in HSA.

An important issue connected with conservation chemistry is how to improve the storage and exposure conditions in order to suppress the fading and degradation of dyes and other components of paintings. Although the oxygen-free exposure cassettes are commonly known in museums, there is still lack of information in the literature about the effect of anoxic conditions on the degradation of dyes. This study is an attempt to start a database formation on the dyes degradation. Five commercial dyes (indigo, dragon's blood, curcumin, madder, carminic acid) were submitted to accelerated ageing by exposure to intensive light in the visible range in both oxygen-free (anoxia) and -rich conditions. Degradation of the samples was investigated by several analytical techniques (attenuated total reflectance infrared spectroscopy, Raman spectroscopy, reflectance UV-Vis spectroscopy, X-ray fluorescence spectroscopy and optical microscopy). The conclusions are based on the estimators (derived from the determination of colour differences from Vis spectra and from the changes in FTIR and Raman vibrational bands intensity). According to them, only indigo, dragon's blood and curcumin show greater stability in anoxic conditions in comparison with oxygen-rich ones while madder, carminic acid undergo greater degradation.

Fluorescence quenching of [Ru(bpy)3]2+ by a series of organic dyes has been investigated by using the steady state fluorescence technique in aqueous medium. The dyes used are anthraquinone dyes: uniblue, acid blue 129, alizarin, alizarin red S and the azo dyes: congo red, sunset yellow, methyl orange, tartrazine, acid orange 63, methyl red and erichrome black T. The quenching of [Ru(bpy)3]2+ was found to obey the Stern-Volmer equation and the corresponding Stern-Volmer plots were linear indicating dynamic quenching. The quenching rate constants (kq) were calculated from the fluorescence data. The mechanism of quenching was discussed on the basis of the quenching rate constants as well as the reduction potential of dyes. The electron transfer mechanism has been proved by the calculation of Gibbs energy changes (ΔGet) by applying the Rehm-Weller equation.

The red snapper (Lutjanus campechanus) is among the most studied reef fish species in the Gulf of Mexico. Several studies have used counts of annuli in sectioned sagittal otoliths to age red snapper. However, interpretation of the putative first annulus has been a major source of debate among otolith readers throughout the Gulf of Mexico. Our objective was to use the chemical marker alizarin complexone to validate the periodicity of first opaque annulus formation in red snapper otolith sections. Juvenile red snapper were immersed in 100 mg alizarin complexone per L seawater solution in November 2005 and then reared in 6000 l circular tanks until July 2006. Otoliths were then removed from the fish and thin sectioned. All experimental otolith sections displayed a distinct fluorescent mark ranging from 0.62 to 0.96 mm from the core when viewed under the microscope with a rhodamine filter. The diffuse opaque annulus was located distally to the alizarin mark in all specimens (ranging from 0.88 to 1.51 mm). The distal position of the presumptive first annulus relative to the alizarin mark in all specimens indicates that this diffuse opaque annulus in red snapper sectioned otoliths forms during the first winter after hatching. Translucent marginal edges of all otolith sections indicate that first opaque annulus formation is completed by mid-July.

The plant kingdom is a valuable source of new medicinal agents. Traditional synthetic dyes used for staining worms may have some carcinogenic effects; therefore, the use of herbal dyes as an effective alternative may be interesting. The objective of the current study was to evaluate the staining effect of herbal dyes on Fasciola hepatica. Powdered alizarin, henna and curcuma in concentrations of 5, 10 and 20 g/100 mL of distilled water were used to stain a F. hepatica worm according to the carmine staining method. Our criteria for evaluation were the extent of staining on different parts of the worm such as suckers, intestine, testes, spines, ootype, vitelline duct, vitellaria, ovary, uterus and eggs. The results showed that alizarin (10 g/100 mL; 10%, w/v) was a better dye than henna (20 g/100 mL; 20%, w/v) and curcuma (20 g/100 mL; 20%, w/v) for the staining of suckers, branched intestine, vitelline duct and ootype. Although henna stained the whole body of the worm better than curcuma, curcuma had a better staining effect on surface spines, eggs and especially branched testes. In comparison with carmine, the present herbal dyes (alizarin and henna) are cheap and safe and could be potential alternatives for staining F. hepatica and other trematodes.

Alkylation of 1,2-dihydroxyanthraquinone (alizarin) by α-bromoacetone was studied and its β-acetonyl derivative was chemically modified. The composition and structure of the products were confirmed by elemental analysis; UV, IR, PMR, and 13C NMR spectroscopy; and mass spectrometry. The synthesized derivatives were tested as inhibitors of HIV-1 RNase H.

An electrochemical method for identifying anthraquinonic, naphthoquinonic, and related dyes in microsamples is reported. This method is based on the sequential application of oxidative and reductive constant-potential polarization steps coupled with the record of square wave voltammograms to solid microsamples of dyes in contact with aqueous electrolytes. As a result, oxidized/reduced products form a layer on the lateral faces of the dye crystals as suggested by attenuated total reflectance-Fourier transform infrared spectroscopy and atomic force microscopy data. This methodology is applied for characterizing alizarin, purpurin, and natural dyes aloe, cochineal red, madder lake, kermes, shellac, and henna attached to paraffin-impregnated graphite electrodes in contact with aqueous potassium phosphate buffer.

The anticoagulant properties of materials derived from the seeds of Cassia obtusifolia were evaluated against platelet aggregation induced by arachidonic acid (AA), collagen, platelet activating factor (PAF), and thrombin, and these effects were then compared to those of three commercially available compounds. The active constituent of C. obtusifolia seeds was then isolated by silica gel column chromatography and HPLC, after which it was characterized as alizarin (1,2-dihydroxyanthraquinone) by spectroscopic analyses. With regard to 50% inhibitory concentration (IC50) values, alizarin was found to effectively inhibit platelet aggregation induced by AA (IC50, 53.1 M) and collagen (IC50, 6.9 M), whereas the IC50 values of its derivatives, alizarin-3-methyliminodiacetic acid were 46.3M (AA) and 2.7M (collagen). However, 1,4-dihydroxyanthraquinone and 1,8-dihydroxyanthraquinone exerted no anticoagulant activity against platelet aggregation. Moreover, alizarin and alizarin-3-methyliminodiacetic acid were found to be significantly more potent inhibitors against platelet aggregation induced by collagen than aspirin. Furthermore, the effect of alizarin and alizarin-3-methyliminodiacetic acid against platelet aggregation induced by AA was 1.5 and 1.3 times lower than that of aspirin. Taken together, these results indicate that alizarin and alizarin-3-methyliminodiacetic acid may prove useful for the inhibition of platelet aggregation induced by collagen.

In this contribution, the amounts of Ni (nickel) and Al (aluminum) in tilapias (Oreochromis niloticus) were determined using square wave voltammetry (SWV) with glassy carbon working microelectrode with a mercury thin film, platinum counter electrode, and Ag/AgCl reference electrode. Ni was studied through the formation of the dimethylglyoxime-Ni (Ni-DMG) complex, while Al was studied through the formation of the Alizarin R-Al complex. The detection limit found for Ni-DMG and Alizarin R-Al complexes were 1.70 x 10(-7) and 1.0 x 10(-8) mol L(-1), respectively. The voltammetric anodic curves for the Alizarin R-Al complex were recorded over the potential range from -0.8 to -0.05 V while the voltammetric cathodic curve for the Ni-DMG complex was recorded over the potential range from -0.7 to -1.2 V. These methods detected low concentrations of Ni and Al in biological samples efficiently.

Photocatalytic removal of Cr6+ from aqueous solution using dye-sensitized nanoscale ZnO under visible light irradiation was studied in this work. First, nanoscale ZnO was prepared by the co-precipitation method. Then, sensitization of nanoscale ZnO by Alizarin Red S dye followed. Further, nanoscale ZnO and dye-sensitized nanoscale ZnO (designated nanoZnO and nanoZnO*, respectively) were both characterized by various photospectrometry methods, such as scanning electron microscopy (SEM), scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), EDS-mapping, transmission electron microscopy (TEM), and X-ray diffractometry (XRD). It was found that both types of prepared particles are spherical in shape with a size range of 20 to 50 nm. XRD patterns showed that both nanoZnO and nanoZnO* had the same crystalline structure of zincite. In the photocatalytic reduction aspect, effects of different light sources and dosage of nanoZnO* on Cr6+ reduction ([Cr6+]initial = 20 mg/L) were evaluated in this work. Treatment of chromium(VI)-bearing wastewater under the conditions of using 1.0 g/L of nanoZnO*, neutral pH, irradiation of household fluorescence lamps for 6 h and 17 h would yield Cr6+ removal efficiencies of about 68% and 90%, respectively. When the household fluorescence lamps were replaced by visible-light lamps of 400–500 nm in wavelength, the corresponding removal efficiencies dropped to about 50% and 75%, respectively. When nanoZnO* was irradiated by sunlight under almost the same experimental conditions, the Cr6+ reduction efficiency increased up to 90%. In summary, sensitizing nanoscale ZnO with Alizarin Red S dye for photocatalytic applications using visible light is feasible. The relevant reaction mechanism and pathways were also proposed in this work.

Staphylococcal biofilms are problematic and play a critical role in the persistence of chronic infections because of their abilities to tolerate antimicrobial agents. Thus, the inhibitions of biofilm formation and/or toxin production are viewed as alternative means of controlling Staphylococcus aureus infections. Here, the antibiofilm activities of 560 purified phytochemicals were examined. Alizarin at 10 μg/ml was found to efficiently inhibit biofilm formation by three S. aureus strains and a Staphylococcus epidermidis strain. In addition, two other anthraquinones purpurin and quinalizarin were found to have antibiofilm activity. Binding of Ca2+ by alizarin decreased S. aureus biofilm formation and a calcium-specific chelating agent suppressed the effect of calcium. These three anthraquinones also markedly inhibited the hemolytic activity of S. aureus and in-line with their antibiofilm activities, increased cell aggregation. A chemical structure-activity relationship study revealed that two hydroxyl units at the C-1 and C-2 positions of anthraquinone play important roles in antibiofilm and anti-hemolytic activities. Transcriptional analyses showed that alizarin repressed the α-hemolysin hla gene, biofilm-related genes (psmα, rbf and spa) and modulated the expressions of cid/lrg genes (the holin/antiholin system). These findings suggest anthraquinones, especially alizarin, are potentially useful for controlling biofilm formation and the virulence of S. aureus.