Ethnopharmacobotany and Diversity of Mediterranean Endemic Plants in Marmilla Subregion, Sardinia, Italy

Human populations in various regions across the world exploit the medicinal properties of plants to treat a wide variety of diseases. Areas with both high rates of endemic taxa and persisting traditional uses of the local botanical resources are key sites for the investigation of Traditional Botanical Knowledge (TBK). Commonly, in these areas, information regarding the medicinal properties of native plants has been transmitted orally from generation to generation, however, a rapid decline in this knowledge has been observed, which can be attributed to socio-economic changes in recent years. The Mediterranean basin is one such site, where human history is intimately entwined with nature. The unique geographical situation and unrivaled environmental heterogeneity of the area, have allowed both the development of diverse civilizations as well as providing the basis for the evolution of extraordinary biodiversity. The Mediterranean basin can therefore be considered a global hotspot of endemic vascular plants, and of traditional knowledge of medicinal and aromatic species. This study researches the historical subregion of Marmilla (central-southern Sardinia, Italy), which was chosen because of its specific cultural and demographic characteristics: i.e., prolonged isolation and extreme longevity of the inhabitants of the area. Semi-structured interviews were conducted with 145 people from the region, and 137 medicinal plants belonging to 62 families were identified, of which around 57,3% were taxa exclusive to the Mediterranean Basin. Findings showed that the most used parts of the plant were the leaves (49%), while as far as preparations are concerned, decoction (50%) was the most used to prepare medicinal formulations, making this the highest number of medico-botanical taxa reported in a study carried out in Sardinia using a similar methodology. In addition, this study contributes towards preventing the loss of TBK by documenting the medicinal traditions, passed down orally for centuries, in the words of the participants, shedding new light on the traditional knowledge of the inhabitants of the island. The findings lay the foundations for future applied studies in the fields of phytotherapy and phytochemical investigation.

Enzyme immobilization on metal organic frameworks: Laccase from Aspergillus sp. is better adapted to ZIF-zni rather than Fe-BTC

Laccase from Aspergillus sp. (LC) was immobilized within Fe-BTC and ZIF-zni metal organic frameworks through a one-pot synthesis carried out under mild conditions (room temperature and aqueous solution). The Fe-BTC, ZIF-zni MOFs, and the LC@Fe-BTC, LC@ZIF-zni immobilized LC samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The kinetic parameters (K_M and V_max) and the specific activity of the free and immobilized laccase were determined. Immobilized LCs resulted in a lower specific activity compared with that of the free LC (7.7 µmol min^-1 mg^-1). However, LC@ZIF-zni was almost 10 times more active than LC@Fe-BTC (1.32 µmol min^-1 mg^-1 vs 0.17 µmol min^-1 mg^-1) and only 5.8 times less active than free LC. The effect of enzyme loading showed that LC@Fe-BTC had an optimal loading of 45.2 mg g^-1, at higher enzyme loadings the specific activity decreased. In contrast, the specific activity of LC@ZIF-zni increased linearly over the loading range investigated. The storage stability of LC@Fe-BTC was low with a significant decrease in activity after 5 days, while LC@ZIF retained up to 50% of its original activity after 30 days storage. The difference in activity and stability between LC@Fe-BTC and LC@ZIF-zni is likely due to release of Fe³⁺ and the low stability of Fe-BTC MOF. Together, these results indicate that ZIF-zni is a superior support for the immobilization of laccase.

The Anti-Microbial Peptide (Lin-SB056-1)2-K Reduces Pro-Inflammatory Cytokine Release through Interaction with Pseudomonas aeruginosa Lipopolysaccharide

The ability of many anti-microbial peptides (AMPs) to modulate the host immune response has highlighted their possible therapeutic use to reduce uncontrolled inflammation during chronic infections. In the present study, we examined the anti-inflammatory potential of the semi-synthetic peptide lin-SB056-1 and its dendrimeric derivative (lin-SB056-1)₂-K, which were previously found to have anti-microbial activity against Pseudomonas aeruginosa in in vivo-like models mimicking the challenging environment of chronically infected lungs (i.e., artificial sputum medium and 3-D lung mucosa model). The dendrimeric derivative exerted a stronger anti-inflammatory activity than its monomeric counterpart towards lung epithelial- and macrophage-cell lines stimulated with P. aeruginosa lipopolysaccharide (LPS), based on a marked decrease (up to 80%) in the LPS-induced production of different pro-inflammatory cytokines (i.e., IL-1β, IL-6 and IL-8). Accordingly, (lin-SB056-1)₂-K exhibited a stronger LPS-binding affinity than its monomeric counterpart, thereby suggesting a role of peptide/LPS neutralizing interactions in the observed anti-inflammatory effect. Along with the anti-bacterial and anti-biofilm properties, the anti-inflammatory activity of (lin-SB056-1)₂-K broadens its therapeutic potential in the context of chronic (biofilm-associated) infections.

Antioxidant, Antimicrobial, and Other Biological Properties of Pompia Juice

Pompia is a Citrus species belonging to Sardinian endemic biodiversity. Health benefits were attributed to its flavedo rind extracts and essential oils while the juice qualities have never been investigated. In this paper, the antioxidant, antimicrobial, and other biological properties of Pompia juice were studied. A combined LCMS/electrochemical/biological approach was used to clarify a still debated phylogeny of this species and to explain the role of its juice phenolic compounds. A closer phylogenetic relationship with lemon and citron, rather than oranges was suggested. Sensors-based electrochemical measures, together with LCMS qualitative and quantitative analyses, revealed a high contribution of ascorbic acid and phenolics with low redox potential, isorhamnetin 3-O-rutinoside, diosmin, and diosmetin 6,8-diglucoside, to antioxidant capacity. The biological assays demonstrated a marked effect of low concentration of Pompia juice against reactive oxygen species (ROS) starting from 50 µg mL⁻¹, and a moderate capacity to reduce ROS damages on cell membrane. Treatments with Pompia juice also resulted in a significant reduction (20%) of the metabolic activity of SW48 colon cancer cells. Lastly, MIC, MBC, and MBIC antimicrobial assays demonstrated that Pompia and lemon juices have inhibitory and antibiofilm effects against the pathogenic bacteria Pseudomonas aeruginosa, Streptococcus aureus, and Enterococcus faecalis.

Assembly of Multicomponent Nano-Bioconjugates Composed of Mesoporous Silica Nanoparticles, Proteins, and Gold Nanoparticles

The purpose of this work was the assembly of multicomponent nano-bioconjugates based on mesoporous silica nanoparticles (MSNs), proteins (bovine serum albumin, BSA, or lysozyme, LYZ), and gold nanoparticles (GNPs). These nano-bioconjugates may find applications in nanomedicine as theranostic devices. Indeed, MSNs can act as drug carriers, proteins stabilize MSNs within the bloodstream, or may have therapeutic or targeting functions. Finally, GNPs can either be used as contrast agents for imaging or for photothermal therapy. Here, amino-functionalized MSNs (MSN-NH2) were synthesized and characterized through various techniques (small angle X-rays scattering TEM, N2 adsorption/desorption isotherms, and thermogravimetric analysis (TGA)). BSA or lysozyme were then grafted on the external surface of MSN-NH2 to obtain MSN-BSA and MSN-LYZ bioconjugates, respectively. Protein immobilization on MSNs surface was confirmed by Fourier transform infrared spectroscopy, ζ-potential measurements, and TGA, which also allowed the estimation of protein loading. The MSN-protein samples were then dispersed in a GNP solution to obtain MSN-protein-GNPs nano-bioconjugates. Transmission electron microscopy (TEM) analysis showed the occurrence of GNPs on the MSN-protein surface, whereas almost no GNPs occurred in the protein-free control samples. Fluorescence and Raman spectroscopies suggested that proteins-GNP interactions involve tryptophan residues.

Physiological and Phylogenetic Characterization of Rhodotorula diobovata DSBCA06, a Nitrophilous Yeast

Agriculture and intensive farming methods are the greatest cause of nitrogen pollution. In particular, nitrification (the conversion of ammonia to nitrate) plays a role in global climate changes, affecting the bio-availability of nitrogen in soil and contributing to eutrophication. In this paper, the Rhodotorula diobovata DSBCA06 was investigated for growth kinetics on nitrite, nitrate, or ammonia as the sole nitrogen sources (10 mM). Complete nitrite removal was observed in 48 h up to 10 mM initial nitrite. Nitrogen was almost completely assimilated as organic matter (up to 90% using higher nitrite concentrations). The strain tolerates and efficiently assimilates nitrite at concentrations (up to 20 mM) higher than those previously reported in literature for other yeasts. The best growth conditions (50 mM buffer potassium phosphate pH 7, 20 g/L glucose as the sole carbon source, and 10 mM nitrite) were determined. In the perspective of applications in inorganic nitrogen removal, other metabolic features relevant for process optimization were also evaluated, including renewable sources and heavy metal tolerance. Molasses, corn, and soybean oils were good substrates, and cadmium and lead were well tolerated. Scale-up tests also revealed promising features for large-scale applications. Overall, presented results suggest applicability of nitrogen assimilation by Rhodotorula diobovata DSBCA06 as an innovative tool for bioremediation and treatment of wastewater effluents.

Agarose and Its Derivatives as Supports for Enzyme Immobilization

Agarose is a polysaccharide obtained from some seaweeds, with a quite particular structure that allows spontaneous gelation. Agarose-based beads are highly porous, mechanically resistant, chemically and physically inert, and sharply hydrophilic. These features-that could be further improved by means of covalent cross-linking-render them particularly suitable for enzyme immobilization with a wide range of derivatization methods taking advantage of chemical modification of a fraction of the polymer hydroxyls. The main properties of the polymer are described here, followed by a review of cross-linking and derivatization methods. Some recent, innovative procedures to optimize the catalytic activity and operational stability of the obtained preparations are also described, together with multi-enzyme immobilized systems and the main guidelines to exploit their performances.

Note. Xylose Production from Durum Wheat Bran: Enzymic versus Chemical Methods

Both acidic and enzymic hydrolytic processes of durum wheat bran to obtain high xylose syrups are discussed in terms of yields and operative conditions. Mild sulphuric hydrolysis gave the best results (400mg of aldopentoses per gram of pre-extracted wheat bran within 4–6 h) whereas hydrochloric and especially phosphoric acids led to low yields. Preliminary work with a highly active recombinant xylanase (endoxylanase) led to deep solubilisation of arabinoxylans, mainly leading to oligosaccharides and their acyl (essentially feruloyl) derivatives. Mild sulphuric hydrolysis still seems to be the treatment of choice for xylose recovery from durum wheat bran.

Aflatoxin B₁ and M₁ Degradation by Lac2 from Pleurotus pulmonarius and Redox Mediators

Laccases (LCs) are multicopper oxidases that find application as versatile biocatalysts for the green bioremediation of environmental pollutants and xenobiotics. In this study we elucidate the degrading activity of Lac2 pure enzyme form Pleurotus pulmonarius towards aflatoxin B₁ (AFB₁) and M₁ (AFM₁). LC enzyme was purified using three chromatographic steps and identified as Lac2 through zymogram and LC-MS/MS. The degradation assays were performed in vitro at 25 °C for 72 h in buffer solution. AFB₁ degradation by Lac2 direct oxidation was 23%. Toxin degradation was also investigated in the presence of three redox mediators, (2,2′-azino-bis-[3-ethylbenzothiazoline-6-sulfonic acid]) (ABTS) and two naturally-occurring phenols, acetosyringone (AS) and syringaldehyde (SA). The direct effect of the enzyme and the mediated action of Lac2 with redox mediators univocally proved the correlation between Lac2 activity and aflatoxins degradation. The degradation of AFB₁ was enhanced by the addition of all mediators at 10 mM, with AS being the most effective (90% of degradation). AFM₁ was completely degraded by Lac2 with all mediators at 10 mM. The novelty of this study relies on the identification of a pure enzyme as capable of degrading AFB₁ and, for the first time, AFM₁, and on the evidence that the mechanism of an effective degradation occurs via the mediation of natural phenolic compounds. These results opened new perspective for Lac2 application in the food and feed supply chains as a biotransforming agent of AFB₁ and AFM₁.

Immobilized Lignin Peroxidase-Like Metalloporphyrins as Reusable Catalysts in Oxidative Bleaching of Industrial Dyes

Synthetic and bioinspired metalloporphyrins are a class of redox-active catalysts able to emulate several enzymes such as cytochromes P450, ligninolytic peroxidases, and peroxygenases. Their ability to perform oxidation and degradation of recalcitrant compounds, including aliphatic hydrocarbons, phenolic and non-phenolic aromatic compounds, sulfides, and nitroso-compounds, has been deeply investigated. Such a broad substrate specificity has suggested their use also in the bleaching of textile plant wastewaters. In fact, industrial dyes belong to very different chemical classes, being their effective and inexpensive oxidation an important challenge from both economic and environmental perspective. Accordingly, we review here the most widespread synthetic metalloporphyrins, and the most promising formulations for large-scale applications. In particular, we focus on the most convenient approaches for immobilization to conceive economical affordable processes. Then, the molecular routes of catalysis and the reported substrate specificity on the treatment of the most diffused textile dyes are encompassed, including the use of redox mediators and the comparison with the most common biological and enzymatic alternative, in order to depict an updated picture of a very promising field for large-scale applications.

Fungal laccases as tools for biodegradation of industrial dyes

Laccases are blue copper oxidases, found in some plants and secreted by a wide range of ligninolytic fungi. These enzymes are well known for their ability in oxidizing several organic compounds, mainly phenolics and aromatic amines, at the expenses of molecular oxygen. Therefore, they could find application in the field of enzymatic bioremediation of many industrial wastewaters, and in particular to bleach and/or detoxify dye-containing effluents. Not all industrial dyes behave as laccase substrates, but this limitation is often overcome by the judicious use of redox mediators. These could substantially widen the application range of laccases as bioremediation tools. The present study encompasses the main properties of the most used industrial dyes as related to their chemical classification, fungal laccases and their molecular and catalytic features, the use of redox mediators, limitations and perspectives of the use of fungal laccases for industrial dye bleaching.

Structure-Activity Relationship Study of Hydroxycoumarins and Mushroom Tyrosinase

The structure-activity relationships of four hydroxycoumarins, two with the hydroxyl group on the aromatic ring of the molecule and two with the hydroxyl group replacing hydrogen of the pyrone ring, and their interactions with mushroom tyrosinase were studied. These compounds displayed different behaviors upon action of the enzyme. The two compounds, ar-hydroxylated 6-hydroxycoumarin and 7-hydroxycoumarin, were both weak substrates of the enzyme. Interestingly, in both cases, the product of the catalysis was the 6,7-hydroxycoumarin, although 5,6- and 7,8-isomers could also theoretically be formed. Additionally, both were able to reduce the formation of dopachrome when tyrosinase acted on its typical substrate, L-tyrosine. Although none of the compounds that contained a hydroxyl group on the pyrone ring were substrates of tyrosinase, the 3-hydroxycoumarin was a potent inhibitor of the enzyme, and the 4-hydroxycoumarin was not an inhibitor. These results were compared with those obtained by in silico molecular docking predictions to obtain potentially useful information for the synthesis of new coumarin-based inhibitors that resemble the structure of the 3-hydroxycoumarin.

Inorganic materials as supports for covalent enzyme immobilization: methods and mechanisms

Several inorganic materials are potentially suitable for enzymatic covalent immobilization, by means of several different techniques. Such materials must meet stringent criteria to be suitable as solid matrices: complete insolubility in water, reasonable mechanical strength and chemical resistance under the operational conditions, the capability to form manageable particles with high surface area, reactivity towards derivatizing/functionalizing agents. Non-specific protein adsorption should be always considered when planning covalent immobilization on inorganic solids. A huge mass of experimental work has shown that silica, silicates, borosilicates and aluminosilicates, alumina, titania, and other oxides, are the materials of choice when attempting enzyme immobilizations on inorganic supports. More recently, some forms of elemental carbon, silicon, and certain metals have been also proposed for certain applications. With regard to the derivatization/functionalization techniques, the use of organosilanes through silanization is undoubtedly the most studied and the most applied, although inorganic bridge formation and acylation with selected acyl halides have been deeply studied. In the present article, the most common inorganic supports for covalent immobilization of the enzymes are reviewed, with particular focus on their advantages and disadvantages in terms of enzyme loadings, operational stability, undesired adsorption, and costs. Mechanisms and methods for covalent immobilization are also discussed, focusing on the most widespread activating approaches (such as glutaraldehyde, cyanogen bromide, divinylsulfone, carbodiimides, carbonyldiimidazole, sulfonyl chlorides, chlorocarbonates, N-hydroxysuccinimides).

Isolation and characterization of polyphenol oxidase from Sardinian poisonous and non-poisonous chemotypes of Ferula communis (L.)

Ferula communis (L.), a plant belonging to Apiaceae, is widely present in Sardinia, Italy. Currently, interest in F. communis focuses on the presence of two chemotypes in the wild. One chemotype is poisonous to animals, whereas the other chemotype is non-poisonous. Polyphenol oxidase (PPO) has been extracted and partially purified from the two chemotypes of F. communis. The biochemical characterization of the enzymes showed significant differences. In particular, while the two PPOs were not able to use 6- and 7-hydroxycoumarin as substrates, they showed distinct specificity for 6,7- and 7,8-dihydroxycoumarin. Significant differences in the enzyme behavior towards common PPO inhibitors were also observed. In addition, activation energy and activation energy for denaturation were determined, showing significant differences between FP-PPO and FNP-PPO, particularly for denaturation kinetics. The possible roles of the two PPOs in determining differences in composition and toxicity of the two F. communis chemotypes are also discussed.

Evaluation of antioxidant potential of “maltese mushroom” (Cynomorium coccineum) by means of multiple chemical and biological assays

Cynomorium coccineum is an edible, non-photosynthetic plant widespread along the coasts of the Mediterranean Sea. The medicinal properties of Maltese mushroom—one of the oldest vernacular names used to identify this species—have been kept in high regard since ancient times to the present day. We evaluated the antioxidant potential of fresh specimens of C. coccineum picked in Sardinia, Italy. Both aqueous and methanolic extracts were tested by using multiple assay systems (DPPH, FRAP, TEAC, ORAC-PYR). Total phenolics and flavonoids were also determined. Gallic acid and cyanidin 3-O-glucoside were identified as the main constituents and measured. Both extracts showed antioxidant capacities; ORAC-PYR assay gave the highest antioxidant value in both cases. The methanolic extract was further investigated with in vitro biological models of lipid oxidation; it showed a significant activity in preventing cholesterol degradation and exerted protection against Cu²⁺-mediated degradation of the liposomal unsaturated fatty acids. Results of the present study demonstrate that the extracts of C. coccineum show a significant total antioxidant power and also exert an in vitro protective effect in different bio-assays of oxidative stress. Therefore, Maltese mushroom can be considered a valuable source of antioxidants and phytochemicals useful in the preparation of nutraceuticals and functional foods.

Degradation of textile dyes using immobilized lignin peroxidase-like metalloporphines under mild experimental conditions

Background

Synthetic dyes represent a broad and heterogeneous class of durable pollutants, that are released in large amounts by the textile industry. The ability of two immobilized metalloporphines (structurally emulating the ligninolytic peroxidases) to bleach six chosen dyes (alizarin red S, phenosafranine, xylenol orange, methylene blue, methyl green, and methyl orange) was compared to enzymatic catalysts. To achieve a green and sustainable process, very mild conditions were chosen.

Results

IPS/MnTSPP was the most promising biomimetic catalyst as it was able to effectively and quickly bleach all tested dyes. Biomimetic catalysis was fully characterized: maximum activity was centered at neutral pH, in the absence of any organic solvent, using hydrogen peroxide as the oxidant. The immobilized metalloporphine kept a large part of its activity during multi-cycle use; however, well-known redox mediators were not able to increase its catalytic activity. IPS/MnTSPP was also more promising for use in industrial applications than its enzymatic counterparts (lignin peroxidase, laccase, manganese peroxidase, and horseradish peroxidase).

Conclusions

On the whole, the conditions were very mild (standard pressure, room temperature and neutral pH, using no organic solvents, and the most environmental-friendly oxidant) and a significant bleaching and partial mineralization of the dyes was achieved in approximately 1 h. Therefore, the process was consistent with large-scale applications. The biomimetic catalyst also had more promising features than the enzymatic catalysts.

[Synergistic exposure to noise and styrene and cochlear functionality in a sample of exposed workers: preliminary results]

This study is aimed at testing the cochlear functionality using otoacoustic emissions, analyzing the synergistic effects of simultaneous exposure to noise and organic solvents EBTx on workers of a glass-reinforced plastic products factory. Exposure to organic solvents was assessed using ambiental measurements and evaluation of the salivary concentration. Biological monitoring was performed evaluating the urinary concentration of the styrene metabolites. Statistical analysis shows that otoacoustic tests can discriminate between different exposure groups. Significant differences were found between controls and subjects exposed to high styrene and low noise levels, showing the ototoxic effect (at sub-clinical level) of the styrene exposure.

Vanilloid derivatives as tyrosinase inhibitors driven by virtual screening-based QSAR models

A number of vanilloids have been tested as tyrosinase inhibitors using Ligand-Based Virtual Screening (LBVS) driven by QSAR (Quantitative Structure-Activity Relationship) models as the multi-agent classification system. A total of 81 models were used to screen this family. Then, a preliminary cluster analysis of the selected chemicals was carried out based on their bioactivity to detect possible similar substructural features among these compounds and the active database used in the QSAR model construction. The compounds identified were tested in vitro to corroborate the results obtained in silico. Among them, two chemicals, isovanillin (K(M) (app) = 1.08 mM) near to kojic acid (reference drug) in one cluster and isovanillyl alcohol (K(M) (app) = 0.88 mM) at the same distance as hydroquinone (reference drug) in another cluster showed inhibitory activity against tyrosinase. The algorithm proposed here could result in a suitable approach for faster and more effective identification of hit and/or lead compounds with tyrosinase inhibitory activity, helping to shorten the long pipeline in the research of novel depigmenting agents to treat skin disorders.

Nucleotide recognition and phosphate linkage hydrolysis at a lipid cubic interface

Mononucleotides, when entrapped within a mono-olein-based cubic Ia3d liquid crystalline phase, have been found to undergo hydrolysis at the sugar-phosphate ester bond in spite of their natural inertness toward hydrolysis. Here, kinetics of the hydrolysis reaction and interactions between the lipid matrix and the mononucleotide adenosine 5'-monophosphate disodium salt (AMP) and its 2'-deoxy derivative (dAMP) are thoroughly investigated in order to shed some light on the mechanism of the nucleotide recognition and phosphate ester hydrolysis. Experiments evidenced that molecular recognition occurs essentially through the sn-2 and the sn-3 alcoholic OH groups of mono-olein. As deduced from the apparent activation energies, the mechanism underlying the hydrolysis reaction is the same for AMP and dAMP. Nevertheless, the reaction proceeds slower for the latter, highlighting a substantial difference in the chemical behavior of the two nucleotides. A model that explains the hydrolysis reaction is presented. Remarkably, the hydrolysis mechanism appears to be highly specific for the Ia3d phase.

Umbelliferone and esculetin: inhibitors or substrates for polyphenol oxidases?

Recently, an interesting debate arose about the nature (substrate versus inhibitor) of esculetin, a coumarin derivative, for mushroom polyphenol oxidase (PPO). The present study examined the behavior of PPOs preparations from fungal and plant origin towards esculetin as a substrate. Both enzymes were able to oxidize esculetin though at a slow rate. A higher sensitivity was reached when the assay was performed in the presence of 3-methyl-2-benzothiazolinone hydrazone (MBTH) even with a lower amount of PPO. These observations unambiguously confirmed that esculetin has to be considered a substrate for mushroom polyphenol oxidase. The oxidation of esculetin was also demonstrated for the first time by a fungal laccase. This should be taken into account because some mushroom PPO preparations could exert contaminant laccase activity. In addition, a PPO preparation from Ferula communis was demonstrated to use esculetin as a substrate. Umbelliferone, the monophenolic precursor of esculetin along the phenylpropanoid pathway, behaved as a competitive inhibitor for the monophenolase activity of mushroom PPO with a K(i) value=0.014 mM. This is worth a mention because only a few couples of mono- and corresponding o-diphenol show such opposite behavior towards PPO. A possible role of PPO in the esculetin fate along biosynthesis pathway of coumarin derivatives is also discussed.

Mediterranean shrubs as potential antioxidant sources

Several Mediterranean shrubs, both autochthonous and naturalized, have been traditionally used as food, flavouring and/or spicing agents, and as phytopharmaceuticals. The interest around 'natural' and 'biological' products is steadily increasing in developed countries. Therefore, it seems reasonable to screen some shrubs with regard to the actual information about their content of phytochemicals, in relation to both real and putative beneficial properties, and with particular concern to their 'antioxidant' power. Moreover, striking molecules from the examined shrubs are compared according to their occurrence in the various genera. Also, their structures and structure/activity relationship are discussed in the light of possible practical application.

Supercritical CO2 extract of Cinnamomum zeylanicum: chemical characterization and antityrosinase activity

The volatile oil of the bark of Cinnamomum zeylanicum was extracted by means of supercritical CO2 fluid extraction in different conditions of pressure and temperature. Its chemical composition was characterized by GC-MS analysis. Nineteen compounds, which in the supercritical extract represented >95% of the oil, were identified. (E)-Cinnamaldehyde (77.1%), (E)-beta-caryophyllene (6.0%), alpha-terpineol (4.4%), and eugenol (3.0%) were found to be the major constituents. The SFE oil of cinnamon was screened for its biological activity about the formation of melanin in vitro. The extract showed antityrosinase activity and was able to reduce the formation of insoluble flakes of melanin from tyrosine. The oil also delayed the browning effect in apple homogenate. (E)-Cinnamaldehyde and eugenol were found to be mainly responsible of this inhibition effect.

Tyrosinase activity and hemocyanin in the hemolymph of the slipper lobster Scyllarides latus

The respiratory protein hemocyanin is present in molluscans and in some species of arthropods, and its dioxygen binding site strongly resembles that of the monophenol-hydroxylating and catechol-quinonising enzyme tyrosinase. Moreover, some hemocyanins show a certain extent of tyrosinase activity, so a common ancestry between the two proteins has been suggested. However, in the case purified hemocyanin of Scyllarides latus any attempts to evoke tyrosinase activity failed. A distinct tyrosinase has been purified to homogeneity from the hemolymph, and kinetically characterised. The purified tyrosinase showed both monophenolase and diphenolase enzyme activity and therefore it could be well defined as a true tyrosinase. This finding suggests that in the case of the studied crustacean the evolutionary functional divergence between dioxygen transport and oxidation of phenolics has already reached its completeness.

Interference of some tryptophan metabolites in the formation of melanin in vitro

Melanin (eumelanin) is commonly produced in mammals starting from tyrosine and/or 3,4-dioxyphenylalanine (DOPA) under the action of tyrosinase. 3-Hydroxyanthranilic acid and 3-hydroxykynurenine are intermediates occurring in the kynurenine pathway of tryptophan catabolism. In this paper, we show that these substances can interfere in melanin formation in vitro when tyrosine or DOPA is oxidized by molecular oxygen under catalysis by tyrosinase. In particular, when 3-hydroxyanthranilic acid is present, a brown and apparently water-soluble pigment is formed, whereas the typical eumelanin granules seem to become more and more rare as the concentration of 3-hydroxyanthranilic acid increases. Also in the presence of the latter, the rate of tyrosine and/or DOPA consumption decreases. A very complicated (13)C-NMR spectrum indicates the high complexity of the reaction. This involves both the true melanin precursor(s) and the tryptophan metabolite, even if with peculiar mechanism and kinetics. When 3-hydroxykynurenine is substituted for 3-hydroxyanthranilic acid the reaction leads to reddish pigments whereas xanthommatins (the typical oxidation products of 3-hydroxykynurenine) are absent. A possible relationship between some dischromic pathologies and tryptophan metabolic disorders is suggested.

Degradation of juglone by Pleurotus sajor-caju

The toxic naphthoquinone juglone (5-hydroxy-1,4-naphthoquinone) is efficiently degraded by the ligninolytic fungus Pleurotus sajor-caju, as demonstrated by the total bleaching within 9 d of a conventional liquid culture medium supplemented with 0.6 mM juglone. The oxidative degradation involves the production of hydrogen peroxide arising from both enzymic and non-enzymic oxidation reactions, promoted by the fungus. Juglone is not directly attacked by the oxidative enzymes of the ligninolytic machinery of P. sajor-caju, such as laccase, manganese peroxidase and arylalcohol oxidase. On the other hand, this naphthoquinone is a good substrate for a reductase, which triggers an auto-oxidative process producing reactive oxygen species and leading to juglone degradation. The degradation process continues to completion by means of a direct, presumably non-catalysed reaction with hydrogen peroxide.

3-hydroxykynurenine as a substrate/activator for mushroom tyrosinase

3-Hydroxykynurenine is a tryptophan metabolite with an o-aminophenol structure. It is both a tyrosinase activator and a substrate, reducing the lag phase, stimulating the monophenolase activity, and being oxidized to xanthommatin. In the early stage of monophenol hydroxylation, catechol accumulation takes place, whereas 3-hydroxykynurenine is substantially unchanged and no significant amounts of the o-quinone are produced. These results suggest an activating action of 3-hydroxykynurenine toward o-hydroxylation of monophenols. 3-Hydroxykynurenine could therefore well act as a physiological device to control phenolics metabolism to catechols and quinonoids.

Tyrosinase inhibition: general and applied aspects

The active site of tyrosinase is described with a view to depicting its interactions with substrates and inhibitors. Occurrence and mechanism(s) of tyrosinase-mediated browning of agrofood products are reviewed, with regard to both enzymic and chemical reactions, and their control, modulation, and inhibition. Technical and applicational implications are discussed.

Effects of plant-derived naphthoquinones on the growth of Pleurotus sajor-caju and degradation of the compounds by fungal cultures

The growth of the white-rot basidiomycete Pleurotus sajor-caju in malt-agar plates was inhibited by three naturally occurring, plant-derived naphthoquinones: juglone, lawsone, and plumbagin. The latter two compounds exerted the most potent antifungal activity, and lawsone killed the mycelium at concentrations higher than 200 ppm. Plates containing juglone and lawsone presented large decolorized areas extending from area of fungal growth, suggesting an extracellular enzymatic degradation of these quinones. Screening of culture plates for extracellular enzymatic activities revealed the presence of both laccase and veratryl alcohol oxidase in most plates, the diffusion of both enzymes matching the decolorized area. In agitated cultures, the presence of juglone was found to stimulate the production of veratryl alcohol oxidase in a significant manner. This is the first time degradation of plant derived naphthoquinones by a white-rot fungus is reported.

Quantitative evaluation of oxidative stress, chronic inflammatory indices and leptin in cancer patients: correlation with stage and performance status

In advanced cancer patients, the oxidative stress could take place either at the onset of disease or as a function of disease progression. To test this hypothesis, the following parameters were investigated: the erythrocyte activity of the enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), the serum activity of glutathione reductase (GR) and the serum total antioxidant status (TAS). The total antioxidant capacity of plasma LMWA was evaluated by the cyclic voltammetry methodology. We further determined the serum levels of proinflammatory cytokines (IL-6 and TNFalpha), IL-2, leptin and C-reactive protein (CRP). All of these parameters have been correlated with the most important clinical indices of patients such as Stage of disease, ECOG PS and clinical response. Eighty-two advanced stage cancer patients and 36 healthy individuals used as controls were included in the study. Our findings show that SOD activity was significantly higher in cancer patients than in controls and GPx activity was significantly lower in cancer patients than in controls. Serum values of IL-6, TNFalpha and CRP were significantly higher in patients than in controls. Serum leptin values of cancer patients were significantly lower than controls. SOD activity increased significantly from Stage II/ECOG 0-1 to Stage IV/ECOG 0-1, whereas it decreased significantly in Stage IV/ECOG 3. GPx activity decreased significantly in Stage IV/ECOG 2-3. An inverse correlation between ECOG PS and serum leptin levels was found. Serum levels of IL-2 decreased from Stage II/ECOG 0-1 to Stage IV/ECOG 2-3. A direct correlation between Stage/ECOG PS and serum levels of both IL-6 and CRP was observed. Cisplatin administration induced a significant increase of GPx after 24 hr. In conclusion, this is the first study that shows that several "biological" parameters of cancer patients such as antioxidant enzyme activity, cytokines, leptin and CRP strictly correlate with the most important clinical parameters of disease such as Stage and ECOG PS.

Copper-promoted overall transformation of 4-tert-butylphenol to its para-hydroxyquinonic derivative, 2-hydroxy-5-tert-butyl-1,4-benzoquinone. Biomimetic studies on the generation of topaquinone in copper amine oxidases

Topaquinone (TPQ) is a cofactor present at the active site of copper amine oxidases, derived from a Tyr residue inserted in the polypeptide chain through a copper-dependent but otherwise largely unknown mechanism. A simple model system was developed that permits to obtain the overall transformation of 4-tert-butylphenol, chosen as a model for Tyr, into a TPQ-like, para-hydroxyquinonic structure in the presence of Cu(II)-imidazole mononuclear complexes.

Some aspects of tyrosine secondary metabolism

The origin and fate of some tyrosine secondary metabolites within specialized eukaryotic cells are discussed in the light of our knowledge of the plasma environment to which they are exposed throughout their lifetime. Attention is focused on ar-dihydroxy and -trihydroxy derivatives and the corresponding quinoidal counterparts, as well as on the enzymic activities involved in the formation and degradation of these potentially toxic molecules. Some physiopathological and pharmacological implications of the above-mentioned topics are considered, taking into account the well known toxicity of reactive intermediates in molecular oxygen reduction, as well as the reactivity of both semiquinonic and quinonic products of catecholamine oxidation.

Effect of 3-hydroxyanthranilic acid on mushroom tyrosinase activity

Tyrosinase is a copper containing protein which catalyzes the hydroxylation of monophenols and the oxidation of diphenols to o-quinones. The monophenolase activity of tyrosinase is characterized by a typical lag time. In this paper the influence of 3-hydroxyanthranilic acid on monophenolase activity of tyrosinase is reported. 3-Hydroxyanthranilic acid reduced the lag time of tyrosinase when the enzyme acted on N-acetyl-L-tyrosine and on 4-tert-butylphenol. In the presence of 3-hydroxyanthranilic acid, the reaction product 4-tert-butyl-o-benzoquinone, derived from 4-tert-butylphenol oxidation, was formed at a higher rate than in its absence. The results reported in this paper indicate that 3-hydroxyanthranilic acid could affect the enzymic activity of mushroom tyrosinase probably by acting as a diphenol substrate. A K(m) value of 0.78 mM was calculated for 3-hydroxyanthranilic acid as substrate. When tyrosinase acted on 4-tert-butylphenol, K(m) for 3-hydroxyanthranilic acid as a cofactor was estimated to be 37.5 microM. No effect was observed on the diphenolase activity of the enzyme acting on 4-tert-butylcatechol in the presence of 3-hydroxyanthranilic acid.

Biosynthesis of the topaquinone cofactor in copper amine oxidases--evidence from model studies

Copper amine oxidases utilize 2,4,5-trihydroxyphenylalanine quinone (topaquinone) as a cofactor in enzymatic catalysis. This cofactor is formed from a tyrosine residue through a self-catalytic mechanism with the participation of the copper ion at the active site. Although pathways have been postulated for topaquinone biogenesis, portions of this scheme are still unclear. We utilized 4-tert-butyl-derived models for the putative intermediates of topaquinone generation and studied the effect of Cu(II) and Zn(II) ions on each autoxidative step from dopa- to topaquinone-like compounds at physiological pH (7.4). Several polyvinyl-alcohol-based soluble resins bearing mono- and di-hydroxyphenolic moieties were also prepared, and their tendency to give hydroxyquinonic structures when incubated at alkaline pH values was investigated. Our results confirm (although indirectly) the formation of dopa and dopaquinone during topaquinone biosynthesis. Moreover, we collected evidence that, following the formation of dopa, the role of the active-site copper ion in topaquinone biogenesis would be limited to the catalysis of the two subsequent quinonization steps (i.e. from dopa to dopaquinone and from topa to topaquinone), thus disfavoring the possibility of a direct intervention of the metal ion in the hydroxylation of dopaquinone. In particular, Cu(II) was shown to influence deeply the autoxidation of 1,2,5-trihydroxy-4-tert-butylbenzene, used as model of topa, both increasing the reaction rate and changing its mechanism. The mechanistic implications of these findings for the biogenesis of topaquinone and its analogs at the active site of various amine oxidases are discussed.