Photocatalytic decomposition of selected biologically active compounds in environmental waters using TiO2/polyaniline nanocomposites: Kinetics, toxicity and intermediates assessment.

A comprehensive study of the removal of selected biologically active compounds (pharmaceuticals and pesticides) from different water types was conducted using bare TiO2 nanoparticles and TiO2/polyaniline (TP-50, TP-100, and TP-150) nanocomposite powders. In order to investigate how molecular structure of the substrate influences the rate of its removal, we compared degradation efficiency of the initial substrates and degree of mineralization for the active components of pharmaceuticals (propranolol, and amitriptyline) and pesticides (sulcotrione, and clomazone) in double distilled (DDW) and environmental waters. The results indicate that the efficiency of photocatalytic degradation of propranolol and amitriptyline was higher in environmental waters: rivers (Danube, Tisa, and Begej) and lakes (Moharac, and Sot) in comparison with DDW. On the contrary, degradation efficacy of sulcotrione and clomazone was lower in environmental waters. Further, of the all catalysts applied, bare TiO2 and TP-100 were found to be most effective in the mineralization of propranolol and amitriptyline, respectively, while TP-150 appeared to be the most efficient in terms of sulcotrione and clomazone mineralization. Also, there was no significant toxicity observed after the irradiation of pharmaceuticals or pesticides solutions using appropriate catalysts on rat hepatoma (H-4-II-E), mouse neuroblastoma (Neuro-2a), human colon adenocarcinoma (HT-29), and human fetal lung (MRC-5) cell lines. Subsequently, detection and identification of the formed intermediates in the case of sulcotrione photocatalytic degradation using bare TiO2 and TP-150 showed slightly different pathways of degradation. Furthermore, tentative pathways of sulcotrione photocatalytic degradation were proposed and discussed.

Efficient removal of sulcotrione and its formulated compound Tangenta® in aqueous TiO2 suspension: Stability, photoproducts assessment and toxicity.

The photocatalytic degradation of the herbicide sulcotrione (0.05 mM) and its formulated compound Tangenta® in aqueous suspensions of TiO2 Degussa P25 was examined as a function of the different operational parameters. The optimum of the catalyst loading was found to be 2.0 mg mL(-1) under UVA light. In the first stage of the reaction, the photocatalytic degradation of sulcotrione alone and in Tangenta® followed the pseudo-first order kinetics, in which the heterogeneous catalysis proceeds via OH and holes. Further, it can be concluded that degradation rate of sulcotrione alone is about two times higher compared to formulated compound. The results showed that the disappearance of sulcotrione led to the formation of three organic intermediates and ionic byproducts (Cl(-), SO4(2-), acetate and formate), whereas their mineralization was about 90% after 4 h. Tentative photodegradation pathways were proposed and discussed. Also, there was no significant toxicity observed after the irradiation of sulcotrione solution and Tangenta® formulation using TiO2 catalyst on three mammalian cell lines.

Photocatalytic degradation of the herbicide clomazone in natural water using TiO2: kinetics, mechanism, and toxicity of degradation products.

The photocatalytic degradation of the herbicide clomazone (0.05mM) in aqueous suspensions of TiO2 Degussa P25 was examined as a function of the different operational parameters. The optimum concentration of the catalyst was found to be 0.50mgmL(-1) under UV light at the pH 10.3. In the first stage of the reaction, the photocatalytic degradation of clomazone followed the pseudo-first order kinetics, with and the heterogeneous catalysis proceeding via OH radicals. The results also showed that the disappearance of clomazone led to the formation of a number of organic intermediates and ionic byproducts, whereas its complete mineralization occurred after about 55min. Tentative photodegradation pathways were proposed and discussed. A comparison of the evolution of toxicity that was evaluated in vitro in rat hepatoma (H-4-II-E) and human fetal lung (MRC-5) cell lines with the degradation kinetics indicates that the irradiation contributed to the decrease of the toxicity of the mixture that is no longer dominated by the parent compound. The study also encompassed the effect of the quality of natural water on the rate of removal of clomazone.

Antioxidant activity relationship of phenolic compounds in Hypericum perforatum L.

BACKGROUND: The St John's Wort (Hypericum perforatum; Clusiaceae) has been used in traditional and modern medicine for a long time due to its high content of biologically active phenolics. The purpose of this work was to develop a method for their fractionation and identification, and to determine the most active antioxidant compounds in plant extract. RESULTS: An LC-MS method which enables fast qualitative and semiquantitative analysis was developed. The composition determined is in agreement with the previous results, where 6 flavonoids, 4 naphthodianthrones and 4 phloroglucinols have been identified. Significant antioxidant activity was determined for most of the fractions by DPPH assay (the lowest IC50 of 0.52 µg/ml), NO scavenging (6.11 µg/ml), superoxide scavenging (1.86 µg/ml), lipid peroxidation (0.0079 µg/ml) and FRAP (the highest reduction capacity of 104 mg Fe equivalents/g) assays. CONCLUSION: LC-MS technique has been successfully applied for a quick separation and identification of the major components of H. perforatum fractions. Majority of the fractions analyzed have expressed a very high antioxidative activity when compared to synthetic antioxidants. The antioxidant activity could be attributed to flavonoids and phenolic acids, while phloroglucinols and naphthodianthrones showed no significant activity. It is demonstrated that it is possible to obtain, by fractionation, H. perforatum preparations with significantly increased phloroglucinols-to-naphthodianthrones ratio (up to 95:5).

Liquid chromatography/tandem mass spectrometry study of anti-inflammatory activity of plantain (Plantago L.) species.

To evaluate anti-inflammatory activity of selected Plantago species (P. lanceolata L. and P. major L.) an optimized in vitro test for determination of cyclooxygenase-1 (COX-1) and 12-lipoxygenase (12-LOX) inhibition potency was undertaken. By using intact cell system (platelets) as a source of COX-1 and 12-LOX enzymes and highly sensitive and specific LC-MS/MS technique for detection of main arachidonic acid metabolites formed by COX-1 and 12-LOX, this test provides efficient method for evaluation of anti-inflammatory potential of plant extracts and isolated compounds. Our results validated the well-known COX-1 inhibitory activity of P. lanceolata and P. major methanol extracts (concentration required for 50% inhibition (IC(50)) was 2.00 and 0.65 mg/ml, respectively). Furthermore, 12-LOX inhibitory activity of examined extracts was reported for the first time (IC(50)=0.75 and 1.73 mg/ml for P. lanceolata and P. major, respectively). Although renowned inhibitors, such as acetylsalicylic acid and quercetin showed higher activity, this study verifies P. lanceolata and P. major as considerable anti-inflammatory agents.

Plantain (Plantago L.) species as novel sources of flavonoid antioxidants.

To examine the antioxidant properties of methanol extracts of selected Plantago species (P. argentea Chaix., P. holosteum Scop., P. major L., P. maritima L., and P. media L.), various assays that measure free radical scavenging ability were carried out: DPPH, hydroxyl radical, superoxide anion, and nitric oxide scavenger capacity tests, reducing power (FRAP) assay, and Fe(2+)/ascorbate induced lipid peroxidation. In all of the tests extracts showed a potent antioxidant effect compared with BHT, a well-known synthetic antioxidant, and the extract of P. major, accepted as an official remedy. Besides, in examined extracts the total phenolic amount (ranging from 38.43 to 70.97 mg of GAE/g of dw) and the total flavonoid content (5.31-13.10 mg of QE/g of dw) were determined. Furthermore, the presence and content of selected flavonoids (luteolin-7-O-glucoside, apigenin-7-O-glucoside, luteolin, apigenin, rutin, and quercetin) were studied using LC-MS/MS technique. LC-MS/MS analysis showed noticeable qualitative and quantitative differences between the species according to which the examined Plantago species could be regarded as a possible new source of natural antioxidants. In this study three of the species examined, P. maritima, P. argentea, and P. holosteum, have been analyzed for the first time.

Photodegradation of clopyralid in TiO2 suspensions: identification of intermediates and reaction pathways.

The work is concerned with the kinetics, identification of intermediates and reaction pathways of the photocatalytic degradation of the herbicide clopyralid (3,6-dichloropyridine-2-carboxylic acid) in UV illuminated aqueous suspensions of TiO(2) (Degussa P25). In the investigated concentration range (0.5-3.0 mM) the photocatalytic degradation kinetics of clopyralid in the first stage of the reaction follows approximately a pseudo-first kinetic order. The highest reaction rate was observed at 4 mg mL(-1)of catalyst concentration, the apparent activation energy of the reaction being 7.74 kJ mol(-1). The effect of the presence of hydrogen peroxide, potassium bromate, and ammonium persulfate, acting as electron acceptors along with molecular oxygen, were also studied. By studying the effect of ethanol as a hydroxyl radical scavenger it was shown that the heterogeneous catalysis takes place mainly via hydroxyl radicals. The reaction intermediates (3,6-dichloropyridin-2-ol, 3,6-dichloro hydroxypyridine-2-carboxylic acid, and 3,3',6,6'-tetrachloro-2,4'-bipyridine-2'-carboxylic acid) were identified and the kinetics of their appearance/disappearance was followed by LC-MS/MS (ESI+). Tentative photodegradation pathways were proposed and discussed.