Phenolic substances in the soil-plant system can be oxidized by metal ions, inorganic components, molecular oxygen as well as by phenol-oxidases, giving rise to the formation of products of low or high molecular weight. Interactions of these products with iron, in both reduced and oxidized form, can affect the iron mobility in soil and rhizosphere, and thus its availability to plants. Here we report the results of a study on the complexing and reducing activity of the oxidation products from caffeic acid (CAF), obtained via electrochemical means, towards Fe(III) and Fe(II) in aqueous solution in the 3.0-6.0 pH range. The HPLC analysis of the filtered solutions after the CAF oxidation showed the formation of two main groups of products: (i) CAF oligomers formed through radicalic reactions which do not involve the double bond of the CAF lateral chain and (ii) products where this bond is involved. These oxidation products (COP) were found to interact with both Fe(III) and Fe(II) with formation of soluble and insoluble Fe(Ill)-, and Fe(II)-COP complexes. The COP were found to be able to reduce Fe(III) to Fe(II) mainly at pH < 4.0. A low redox activity was observed at pH greater than or equal to 4.5 due to Fe(III) hydrolysis reactions as well as to the decrease in the redox potential of the Fe(III)/Fe(II) couple. Formation of hydroxy Fe(III)-COP polymers occurs at pH > 3.5.

Urease catalyzes the decomposition of urea to ammonium and carbamate ions by its active site which contains two nickel(II) atoms. Here we report the results of a molecular dynamics investigation performed on a system constituted of the cavity of the enzyme and one hydroxamic acid molecule which acts as an inhibitor of the protein. The results agree with experimental data and represent a valid starting point for the design of more efficient urease inhibitors.

The reduction of Fe(III) by caffeic acid (CAF) in the presence of desferrioxamine-B (DFOB) was studied as a function of pH and time. The HPLC analyses, UV/vis spectra and kinetic data provide evidence that the reduction of Fe(III) by caffeic acid is strongly inhibited by DFOB and that it can be induced by the siderophore at low pH values. The stoichiometry and the possible mechanism of the reduction process are reported.

Summary The reduction of iron(III) by natural humic acid (NHA) was studied in aqueous solution as a function of pH, time and iron(III) concentration. The information gained from FTIR and ESR spectroscopies as well as potentiometric data suggests that redox reactions occur at a low pH due to the involvement of phenolic groups and radicals. At pH values higher than 3.5 the reaction is strongly inhibited by the formation of iron(III)–humate complexes.

The interaction of D-galacturonic acid (HG) with iron(III) and iron(II) ions was studied in aqueous 1 M sodium perchlorate solutions. At pH<3.1, the predominant form of the iron(III) complexes is Fe(III)G3 where the ligand molecules coordinate essentially by the carboxylic group. At higher pH values, complexes with further deprotonated ligand molecules are the main species in the system. There is some evidence that the chelates formed involve the open form of the sugar molecule, the iron(III) ions binding the oxygen corresponding to the ring oxygen of the closed form. In the heterogeneous D-galacturonic acid/Fe(III)-clay system, the sugar molecule appears to interact strongly with the bentonite, suggesting the formation of complex species in which all three components of the ternary system are involved.

The stoichiometry of the reduction reaction and D-galacturonic acid with iron(III) has been determined, leading to a 4:1 ratio between the quantities of reduced iron and oxidized D-galacturonic acid, respectively. This last molecule is oxidized to formic acid, and the residue is thought to present a further terminal carboxylic group. The reducing predominant species appears to be the FeGal3 complex.

The lipidic fraction extracted from Rankers and Cambisols developed under the same pedoclimatic conditions was studied using chemical and physical methods. Their amounts extracted from different horizons varied from 0.10 to 0.66 g/100 g soil or from 2.7 to 33.3 g/100 g soil organic matter. UV-visible, NMR and IR analyses indicate a rather homogeneous constitution of the lipidic fraction of the examined soils, characterized by a prevalence of long aliphatic saturated chains and only traces of aromatic compounds. X-ray diffractometry gives evidence of the presence in all horizons of ozocerite, a crystalline mineral wax which can be considered an accumulation metabolic product. The characteristics of the lipids of these soils, shown by the acid number and by the E 2 /E 3 ratio, can be used as an index of their bioactivity.

We investigated the interaction of Fluazifop-butyl with Na-, Fe(III)-, Al- and Cu-montmorillonite by submitting self-supporting films or powders of clay, previously immersed in a CHCl3 solution of the herbicide, to infrared (IR) and x-ray analysis, respectively. The IR results demonstrate that Fluazifop-butyl is adsorbed onto all homoionic clays by at least two different mechanisms, both depending on the acidic properties of water molecules coordinated to the exchangeable cations. The first, acting for all clays except Na samples, is the protonation of the pyridinic nitrogen atom of the organic molecule followed by adsorption on the clay surfaces. Evidence for this is the apparance on NH stretching that persists after heating at 110°C. The second, regarding also Naclay, is the formation of hydrogen bonds between the ester carbonyl group of the herbicide and the hydration water of metal ions, as evidenced by the shift of C·O stretch toward lower frequencies; dehydration at 110°C causes it to revert to the characteristic value of the free molecule. The adsorption of pesticide is supported also by x-ray analyses: the light increase of d001 values of partially dehydrated organoclay complexes suggests that a single layer of Fluazifop-butyl is present in the interlamellar region of montmorillonite. The CEC of treated samples is lower than that before adsorption because of the hydrophobic nature of the herbicide, which prevents the total exchange of adsorbed cations by neutral salt solutions

Liquid chromatographic separation and detection with catalytic analysis was investigated for highly sensitive and automated fractional determination of vanadium(IV) and -(V). Chromatographic separation between these species was performed with a mixture (pH 3.0) of ethylenediamine and tartaric acid as the eluent and a separation column containing sulphonate groups. The eluent was introduced to an air-segmented continuous flow analysis system based on the catalytic reaction with Bindschedler’s green leuco base. The detection limit of this method was 0.2 nmol dm−3 for both vanadium(IV) and -(V).

Iron forms which characterize the clay fraction of four Cambisols from granite and the distribution of iron oxides in the soil profiles are studied by Mössbauer spectroscopy, X-ray diffractometry and selected chemical methods. The results obtained show that about 50 % of the Fe t (6–10 % Fe) is not extracted by dithionite. The Fe o /Fe d ranges between 0.15 and 0.35. Oxalate dissolves goethite in different amounts, probably depending on the particle size and the Al-substitution level. The highest amount of hematite is found in the samples characterized by the lowest internal magnetic fields, suggesting that the soil distribution of hematite and goethite is related to environmental factors favouring or disfavouring Al-for-Fe substitution and crystallinity of the oxides.

Thymus capitatusHoffm. et Link. is an endemic medicinal plant to the Mediterranean region. It is used in folk medicine to treat various diseases including diabetes, flu, cough, flatulence, dermatitis, indigestion, respiratory disorders, asthma, rheumatic, diarrhea, and influenza. It is also used as antiseptic, analgesic, stimulant, and sedative.In this review, previous reports on T. capitatusconcerningits taxonomy, botanical description, geographical distribution, ethnomedicinal use, phytochemistry, pharmacological properties, and food benefits were critically summarized.Scientificsearch engines including PubMed, ScienceDirect, SpringerLink, Web of Science, Scopus, Wiley Online, Scifnder, and Google Scholar were consulted to gather data on T. capitatus. The data presented in this work summarize T. capitatus phytochemical compounds, ethnomedicinaluses, pharmacological properties, and food value.In traditional medicine, T. capitatusis used to treat various illnesses including diabetes, dermatitis, and diarrhea. The essential oils and extracts of T. capitatus exhibited several biological properties such as antibacterial, antioxidant, antifungal, antiparasitic, hypoglycemic, anticancer, antiviral, and hepatoprotective effects. T. capitatus possesses high nutritional value and its essential oil showed promising activity in food preservation. Phytochemical characterization of T. capitatus revealed the presence of several classes of secondary metabolites such as terpenoids, flavonoids, and phenolic acids.Ethnomedicinal surveys indicated the use of T. capitatus for the treatment of various disorders. Pharmacological reports showed that T. capitatus especially its essential oils, exhibited potent antimicrobial, antioxidant, antidiabetic and hepatoprotective effects. These findings confirmed the link between traditional medicinal use and scientific biological results. Moreover, T. capitatus exhibited a potent food preservative effect which justifies its use in traditional medicine as a food additive.In light of these findings, further studies to validate the industrial applications of T. capitatus essential oils as a food additive are required. Further investigations on the in vivo pharmacological properties of T. capitatus are strongly recommended to validate the results of its clinical uses as an antimicrobial, hepatoprotective, and antiviral agent. Toxicological tests and pharmacokinetic investigations are also needed to validate the safety and efficacy ofT. capitatus and its bioactive compounds.

A study has been made using i.r. and n.m.r. spectroscopic techniques to investigate ten different organic fractions extracted in a series of mild organic solvents from a brown soil from Sardinia. The experimental results gave useful information about the nature of the extracted samples, which differ considerably from one another. Some of the extracts are characterized by a preponderance of aliphatic structures; others, by the presence of quinone-hydroquinone units or polymeric chains; and others, by particular chemical skeletons, probably based upon hydrolylated naphtho- or anthraquinone frameworks.