Washingtonia filifera seed extracts inhibit the islet amyloid polypeptide fibrils formations and α-amylase and α-glucosidase activity.

Washingtonia filifera seeds have revealed to possess antioxidant properties, butyrylcholinesterase and xanthine oxidase inhibition activities. The literature has indicated a relationship between Alzheimer's disease (AD) and type-2 diabetes (T2D). Keeping this in mind, we have now evaluated the inhibitory properties of W. filifera seed extracts on α-amylase, α-glucosidase enzyme activity and the Islet Amyloid Polypeptide (IAPP) fibrils formation. Three extracts from seeds of W. filifera were evaluated for their enzyme inhibitory effect and IC50 values were calculated for all the extracts. The inhibition mode was investigated by Lineweaver-Burk plot analysis and the inhibition of IAPP aggregate formation was monitored. W. filifera methanol seed extract appears as the most potent inhibitor of α-amylase, α-glucosidase, and for the IAPP fibril formation. Current findings indicate new potential of this extract that could be used for the identification or development of novel potential agents for T2D and AD.

Synthesis, molecular docking and cholinesterase inhibitory activity of hydroxylated 2-phenylbenzofuran derivatives.

We have designed, synthesized and evaluated a series of hydroxylated 2-phenylbenzofuran derivatives as potential cholinesterase inhibitors. Starting from a series of 2-phenylbenzofurans previously published, in this paper we present a complete synthesis and the influence on the activity of one or two hydroxyl groups located in meta or in meta and para positions respectively of the 2-phenyl ring and highlight the importance of position of hydroxyl groups. Moreover, simultaneous introduction of halogen at position 7 of the benzofuran scaffold resulted in an improved inhibitory activity against the enzyme. To further provide molecular insight and to identify the most probable ligand-binding site of the protein, docking studies were performed for the top-ranked compounds. Docking results revealed conserved ligand-binding residues and supported the role of catalytic site residues in enzyme inhibition.

Antibacterial Activity and Molecular Docking Studies of a Selected Series of Hydroxy-3-arylcoumarins.

Antibiotic resistance is one of the main public health concerns of this century. This resistance is also associated with oxidative stress, which could contribute to the selection of resistant bacterial strains. Bearing this in mind, and considering that flavonoid compounds are well known for displaying both activities, we investigated a series of hydroxy-3-arylcoumarins with structural features of flavonoids for their antibacterial activity against different bacterial strains. Active compounds showed selectivity against the studied Gram-positive bacteria compared to Gram-negative bacteria. 5,7-Dihydroxy-3-phenylcoumarin (compound 8) displayed the best antibacterial activity against Staphylococcus aureus and Bacillus cereus with minimum inhibitory concentrations (MICs) of 11 g/mL, followed by Staphylococcus aureus (MRSA strain) and Listeria monocytogenes with MICs of 22 and 44 g/mL, respectively. Moreover, molecular docking studies performed on the most active compounds against Staphylococcus aureus tyrosyl-tRNA synthetase and topoisomerase II DNA gyrase revealed the potential binding mode of the ligands to the site of the appropriate targets. Preliminary structure-activity relationship studies showed that the antibacterial activity can be modulated by the presence of the 3-phenyl ring and by the position of the hydroxyl groups at the coumarin scaffold.

Amine oxidase from Euphorbia characias: Kinetic and structural characterization.

This minireview focuses on a plant copper/2,4,5-trihydroxyphenyl alanine quinone amine oxidase isolated from the latex of the shrub Euphorbia characias (ELAO). This enzyme has been investigated in terms of both molecular structure and kinetic mechanism. The characterization of this enzyme allowed us to identify specific amino acids and domains that play a key role in modulating substrate access into the active site not only for ELAO but also for other plant and mammalian amine oxidases. As mammalian amine oxidases are implicated in several physiological and pathological conditions, the deep structural characterization of their active site accession mechanisms could be the starting point for the development of enzyme modulators with high therapeutic potential. Thus, this paper gives structural/functional insights that open new perspectives in the research about the whole amine oxidase family.

New insights into highly potent tyrosinase inhibitors based on 3-heteroarylcoumarins: Anti-melanogenesis and antioxidant activities, and computational molecular modeling studies.

Melanogenesis is a physiological pathway for the formation of melanin. Tyrosinase catalyzes the first step of this process and down-regulation of its activity is responsible for the inhibition of melanogenesis. The search for molecules capable of controlling hyperpigmentation is a trend topic in health and cosmetics. A series of heteroarylcoumarins have been synthesized and evaluated. Compounds 4 and 8 exhibited higher tyrosinase inhibitory activities (IC50=0.15 and 0.38µM, respectively), than the reference compound, kojic acid (IC50=17.9µM). Compound 4 acts as competitive, while compound 8 as uncompetitive inhibitor of mushroom tyrosinase. Furthermore, compounds 2 and 8 inhibited tyrosinase activity and melanin production in B16F10 cells. In addition, compounds 2-4 and 8 proved to have an interesting antioxidant profile in both ABTS and DPPH radicals scavenging assays. Docking experiments were carried out in order to study the interactions between these heteroarylcoumarins and mushroom tyrosinase.

2-Phenylbenzofuran derivatives as butyrylcholinesterase inhibitors: Synthesis, biological activity and molecular modeling.

A series of 2-phenylbenzofurans compounds was designed, synthesized and evaluated as cholinesterase inhibitors. The biological assay experiments showed that most of the compounds displayed a clearly selective inhibition for butyrylcholinesterase (BChE), while a weak or no effect towards acetylcholinesterase (AChE) was detected. Among these benzofuran derivatives, compound 16 exhibited the highest BChE inhibition with an IC50 value of 30.3 µM. This compound was found to be a mixed-type inhibitor as determined by kinetic analysis. Moreover, molecular dynamics simulations revealed that compound 16 binds to both the catalytic anionic site (CAS) and peripheral anionic site (PAS) of BChE and it displayed the best interaction energy value, in agreement with our experimental data.

Tyrosinase inhibition and antioxidant properties of Asphodelus microcarpus extracts.

BACKGROUND: Asphodelus microcarpus belongs to the family Liliaceae that include several medicinal plants. In the traditional medicine plants of the genus Asphodelus are used to treat skin disorders such as ectodermal parasites, psoriasis, microbial infection and for lightening freckles. In order to find novel skin depigmenting agents, the present work was carry out to evaluate antioxidant activity and tyrosinase inhibitory potential of leaves, flowers and tubers extracts of A. microcarpus. The phytochemical composition of the active extract was also evaluated. METHODS: Three different extracts (water, methanol and ethanol) from leaves, flowers and tubers of A. microcarpus were evaluated for their inhibitory effect on tyrosinase activity using L-3,4-dihydroxyphenylalanine (L-DOPA) as substrate. Inhibition of cellular tyrosinase activity and melanin production was also investigated in melanoma B16F10 cells. Antioxidant activity, total phenolic and flavonoids contents were determined using standard in vitro methods. HPLC-DAD-MS was used to identify phenolic profile of the active extract. RESULTS: The results showed that all extracts have a direct inhibitory anti-tyrosinase activity, with ethanolic extract from flowers (FEE) exhibiting the stronger effect. Kinetic analysis revealed that FEE acts as an uncompetitive inhibitor with a Ki value of 0.19 mg/mL. The same effect was observed in murine melanoma B16F10 cells. Cellular tyrosinase activity as well as melanin content were reduced in FEE-treated cells. The results were comparable to that of the standard tyrosinase inhibitor (kojic acid). Furthermore, the same extract showed the highest antioxidant activity and an elevated levels of total phenolics and flavonoid content. Eleven phenolic components were identified as chlorogenic acid, luteolin derivates, naringenin and apigenin. CONCLUSIONS: Our findings showed that FEE from A. microcarpus inhibits tyrosinase and exerted antimelanogenesis effect in B16F10 cells. This extract also showed the highest scavenging activity, which could be mainly attributed to its high levels of total polyphenols and flavonoids. These results suggest that A. microcarpus has a great potential as sources of bioactive compounds which could be used as depigmenting agents in skin disorders.

Chitinase III in Euphorbia characias latex: Purification and characterization.

This paper deals with the purification of a class III endochitinase from Euphorbia characias latex. Described purification method includes an effective novel separation step using magnetic chitin particles. Application of magnetic affinity adsorbent noticeably simplifies and shortens the purification procedure. This step and the subsequently DEAE-cellulose chromatography enable to obtain the chitinase in homogeneous form. One protein band is present on PAGE in non-denaturing conditions and SDS-PAGE profile reveals a unique protein band of 36.5 ± 2 kDa. The optimal chitinase activity is observed at 50 °C, pH 5.0. E. characias latex chitinase is able to hydrolyze colloidal chitin giving, as reaction products, N-acetyl-D-glucosamine, chitobiose and chitotriose. Moreover, we observed that calcium and magnesium ions enhance chitinase activity. Finally, we cloned the cDNA encoding the E. characias latex chitinase. The partial cDNA nucleotide sequence contains 762 bp, and the deduced amino acid sequence (254 amino acids) is homologous to the sequence of several plant class III endochitinases.

Domain mobility as probed by small-angle X-ray scattering may account for substrate access to the active site of two copper-dependent amine oxidases.

Amine oxidases are a family of dimeric enzymes that contain one copper(II) ion and one 2,4,5-trihydroxyphenyalanine quinone per subunit. Here, the low-resolution structures of two Cu/TPQ amine oxidases from lentil (Lens esculenta) seedlings and from Euphorbia characias latex have been determined in solution by small-angle X-ray scattering. The active site of these enzymes is highly buried and requires a conformational change to allow substrate access. The study suggests that the funnel-shaped cavity located between the D3 and D4 domains is narrower within the crystal structure, whereas in solution the D3 domain could undergo movement resulting in a protein conformational change that is likely to lead to easier substrate access.

Analysis of the glycosylation pattern of plant copper amine oxidases by MALDI-TOF/TOF MS coupled to a manual chromatographic separation of glycans and glycopeptides.

The N-glycosylation in pea seedling amine oxidase and lentil seedling amine oxidase was analyzed in the present work. For that purpose, the enzymes were purified as native proteins from their natural sources. An enzymatic deglycosylation of pea seedling amine oxidase by endoglycosidase H under denaturing conditions combined with its proteolytic digestion by trypsin was carried out in order to analyze both N-glycans and "trimmed" N-glycopeptides with a residual N-acetylglucosamine attached at the originally occupied N-glycosylation sites. The released N-glycans were subjected to a manual chromatographic purification followed by MALDI-TOF/TOF MS. MS and MS/MS analyses were also performed directly on peptides and N-glycopeptides generated by proteolytic digestion of the studied enzymes. Sequencing of glycopeptides by MALDI-TOF/TOF MS/MS after their separation on a RP using a microgradient chromatographic device clearly demonstrated binding of paucimannose and hybrid N-glycan structures at Asn558. Such carbohydrates have been reported to exist in many plant N-glycoproteins, e.g. in peroxidases. Although high-mannose glycan structures were identified after the enzymatic deglycosylation, they could not be assigned to a particular N-glycosylation site. The presence of unoccupied glycosylation sites in several peptides was also confirmed from MS/MS results.

Euphorbia characias: Phytochemistry and Biological Activities.

The aim of this review is to summarize all the compounds identified and characterized from Euphorbia characias, along with the biological activities reported for this plant. Euphorbia is one of the greatest genera in the spurge family of Euphorbiaceae and includes different kinds of plants characterized by the presence of milky latex. Among them, the species Euphorbia characias L. is an evergreen perennial shrub widely distributed in Mediterranean countries. E. characias latex and extracts from different parts of the plant have been extensively studied, leading to the identification of several chemical components such as terpenoids, sterol hydrocarbons, saturated and unsaturated fatty acids, cerebrosides and phenolic and carboxylic acids. The biological properties range between antioxidant activities, antimicrobial, antiviral and pesticidal activities, wound-healing properties, anti-aging and hypoglycemic properties and inhibitory activities toward target enzymes related to different diseases, such as cholinesterases and xanthine oxidase. The information available in this review allows us to consider the plant E. characias as a potential source of compounds for biomedical research.

A new biological prospective for the 2-phenylbenzofurans as inhibitors of α-glucosidase and of the islet amyloid polypeptide formation.

In this study, we have investigated a series of hydroxylated 2-phenylbenzofurans compounds for their inhibitory activity against α-amylase and α-glucosidase activity. Inhibitors of carbohydrate degrading enzymes seem to have an important role as antidiabetic drugs. Diabetes mellitus is a wide-spread metabolic disease characterized by elevated levels of blood glucose. The most common is type 2 diabetes, which can lead to severe complications. Since the aggregates of islet amyloid polypeptide (IAPP) are common in diabetic patients, the effect of compounds to inhibit amyloid fibril formation was also determined. All the compounds assayed showed to be more active against α-glucosidase. Compound 16 showed the lowest IC50 value of the series, and it is found to be 167 times more active than acarbose, the reference compound. The enzymatic activity assays showed that compound 16 acts as a mixed-type inhibitor of α-glucosidase. Furthermore, compound 16 displayed effective inhibition of IAPP aggregation and it manifested no significant cytotoxicity. To predict the binding of compound 16 to IAPP and α-glucosidase protein complexes, molecular docking studies were performed. Altogether, our results support that the 2-phenylbenzofuran derivatives could represent a promising candidate for developing molecules able to modulate multiple targets involved in diabetes mellitus disorder.

Anti-Aging Potential of Extracts from Washingtonia filifera Seeds.

The aim of this study was to test the inhibitory effect of fruit extracts from Washingtonia filifera on skin aging-related enzymes. The pulp extracts did not exert a significant enzyme inhibition while seed extracts from W. filifera exhibit anti-elastase, anti-collagenase, and anti-tyrosinase activities. Tyrosinase was mildly inhibited while a stronger effect was observed with respect to elastase and collagenase inhibition. Alcoholic extracts provided better results than aqueous extracts. Among them, methanol extracts showed the prominent enzyme inhibitory activities being IC50 value for elastase and collagenase comparable and even better than the reference compound. The inhibition mode of the most active extracts was investigated by Lineweaver-Burk plot analysis. Seed extracts from W. filifera were also investigated for their photo-protective effect by Mansur equation and the antioxidant activity of W. filifera extract was evaluated in oxidative-stressed cells. To evaluate the safety of the extract, the effect on cell viability of human keratinocytes cells was analyzed. Methanol extract presented the best photo-protective effect and exerted an antioxidant activity in a cellular system with no cytotoxic effect. The overall results demonstrate that W. filifera extracts are promising sources of bioactive compounds that could be used in cosmetic and pharmaceutical preparation.

Euphorbia peroxidase catalyzes thiocyanate oxidation in two different ways, the distal calcium ion playing an essential role.

The oxidation of the pseudohalide thiocyanate (SCN(-)) by Euphorbia peroxidase, in the presence or absence of added calcium, is investigated. After incubation of the native enzyme with hydrogen peroxide, the formation of Compound I occurs and serves to catalyze the thiocyanate oxidation pathways. The addition of a stoichiometric amount of SCN(-) to Compound I leads to the native enzyme spectrum; this process clearly occurs via two electron transfers from pseudohalide to Compound I. In the presence of 10 mM calcium ions, the addition of a stoichiometric amount of SCN(-) to Compound I leads to the formation of Compound II that returns to the native enzyme after addition of a successive stoichiometric amount of SCN(-), indicating that the oxidation occurs via two consecutive one-electron transfer steps. Moreover, different reaction products can be detected when the enzyme-hydrogen peroxide-thiocyanate reaction is performed in the absence or presence of 10 mM Ca(2+) ions. The formation of hypothiocyanous acid is easy demonstrated in the absence of added calcium, whereas in the presence of this ion, CN(-) is formed as a reaction product that leads to the formation of an inactive species identified as the peroxidase-CN(-) complex. Thus, although monomeric, Euphorbia peroxidase is an allosteric enzyme, finely tuned by Ca(2+) ions. These ions either can enhance the catalytic efficiency of the enzyme toward some substrates or can regulate the ability of the enzyme to exploit different metabolic pathways toward the same substrate.

Structure of a nucleotide pyrophosphatase/phosphodiesterase (NPP) from Euphorbia characias latex characterized by small-angle X-ray scattering: clues for the general organization of plant NPPs.

Little information is available concerning the structural features of nucleotide pyrophosphatase/phosphodiesterases (NPPs) of plant origin and the crystal structures of these proteins have not yet been reported. The aim of this study was to obtain insight into these aspects by carrying out a comparative analysis of the sequences of two different fragments of an NPP from the latex of the Mediterranean shrub Euphorbia characias (ELNPP) and by studying the low-resolution structure of the purified protein in solution by means of small-angle X-ray scattering. This is the first structure of a plant NPP in solution that has been reported to date. It is shown that the ELNPP sequence is highly conserved in many other plant species. Of note, the catalytic domains of these plant NPPs have the same highly conserved PDE-domain organization as mammalian NPPs. Moreover, ELNPP is a dimer in solution and this oligomerization state is likely to be common to other plant enzymes.

Shedding light on the presymbiontic phase of C. arietinum.

A complex network of symbiotic events between plants and bacteria allows the biosphere to exploit the atmospheric reservoir of molecular nitrogen. In seeds, a series of presymbiotic steps are already identified during imbibition, while interactions between the host and its symbiont begin in the early stages of germination. In the present study, a detailed analysis of the substances' complex delivered by Cicer arietinum seeds during imbibition showed a relevant presence of proteins and amino acids, which, except for cysteine, occurred with the whole proteinogenic pool. The imbibing solution was found to provide essential probiotic properties able to sustain the growth of the specific chickpea symbiont Mesorhizobium ciceri. Moreover, the imbibing solution, behaving as a complete medium, was found to be critically important for the symbiont's attraction, a fact this that is strictly related to the presence of the amino acids glycine, serine, and threonine. Here, the presence of these amino acids is constantly supported by the presence of the enzymes serine hydroxymethyltransferase and formyltetrahydrofolate deformylase, which are both involved in their biosynthesis. The reported findings are discussed in the light of the pivotal role played by the imbibing solution in attracting and sustaining symbiosis between the host and its symbiont.

Phytochemical composition and the cholinesterase and xanthine oxidase inhibitory properties of seed extracts from the Washingtonia filifera palm fruit.

The chemical composition and biological properties of palm Washingtonia filifera (Lindl.) H. Wendl. seeds are seldom studied. Bearing this in mind, the seeds of W. filifera fruits were analysed for their fatty acid and phenolic composition and their antioxidant activity in addition to their cholinesterase and xanthine oxidase inhibitory activities. Seed extracts were revealed as a good source of phenolics with significant antioxidant activity. The phenolic profile mainly consisted of proanthocyanidins or procyanidin dimers B1-B4 among the major compounds. The highest butyrylcholinesterase inhibitory activity was found in the ethanolic extracts of seeds, with IC50 values of 13.73 ± 1.31 µg mL-1. Seed alcoholic extracts also displayed interesting xanthine oxidase inhibitory activity, with IC50 values ranging between 75.2 ± 17.0 µg mL-1 and 95.8 ± 5.9 µg mL-1. Procyanidin B1, a major component in the extracts, could be an important contributor to that activity, as it was found to possess good xanthine oxidase inhibition capacity (IC50 value of 53.51 ± 6.03 µg mL-1). Docking studies were also performed to predict the binding sites of procyanidins B1 and B2 within the xanthine oxidase structure. In all, W. filifera seeds appear as a promising natural source for the extraction of bioactive compounds with antioxidant and butyrylcholinesterase as well as xanthine oxidase inhibitory potential.

Allosteric modulation of Euphorbia peroxidase by nickel ions.

A class III peroxidase, isolated and characterized from the latex of the perennial Mediterranean shrub Euphorbia characias, contains one ferric iron-protoporphyrin IX pentacoordinated with a histidine 'proximal' ligand as heme prosthetic group. In addition, the purified peroxidase contained 1 mole of endogenous Ca(2+) per mole of enzyme, and in the presence of excess Ca(2+), the catalytic efficiency was enhanced by three orders of magnitude. The incubation of the native enzyme with Ni(2+) causes reversible inhibition, whereas, in the presence of excess Ca(2+), Ni(2+) leads to an increase of the catalytic activity of Euphorbia peroxidase. UV/visible absorption spectra show that the heme iron remains in a quantum mechanically mixed-spin state as in the native enzyme after addition of Ni(2+), and only minor changes in the secondary or tertiary structure of the protein could be detected by fluorescence or CD measurements in the presence of Ni(2+). In the presence of H(2)O(2) and in the absence of a reducing agent, Ni(2+) decreases the catalase-like activity of Euphorbia peroxidase and accelerates another pathway in which the inactive stable species accumulates with a shoulder at 619 nm. Analysis of the kinetic measurements suggests that Ni(2+) affects the H(2)O(2)-binding site and inhibits the formation of compound I. In the presence of excess Ca(2+), Ni(2+) accelerates the reduction of compound I to the native enzyme. The reported results are compatible with the hypothesis that ELP has two Ni(2+)-binding sites with opposite functional effects.

Tyramine oxidation by copper/TPQ amine oxidase and peroxidase from Euphorbia characias latex.

Tyramine, an important plant intermediate, was found to be a substrate for two proteins, a copper amine oxidase and a peroxidase from Euphorbia characias latex. The oxidation of tyramine took place by two different mechanisms: oxidative deamination to p-hydroxyphenylacetaldehyde by the amine oxidase and formation of di-tyramine by the peroxidase. The di-tyramine was further oxidized at the two amino groups by the amino oxidase, whereas p-hydroxyphenylacetaldehyde was transformed to di-p-hydroxyphenylacetaldehyde by the peroxidase. Data obtained in this study indicate a new interesting scenario in the metabolism of tyramine.

Sardinian honeys as sources of xanthine oxidase and tyrosinase inhibitors.

Sardinian honeys obtained from different floral sources (Arbutus, Asphodelus, Eucalyptus, Thistle, and Sulla) were evaluated for their ability to inhibit tyrosinase and xanthine oxidase enzymes and for their antioxidant activity. Physicochemical parameters, total phenolic, and flavonoids content were also determined. Honey from Arbutus flowers had the highest antioxidant activity followed by Eucalyptus and Thistle ones. These three honeys showed good tyrosinase and xanthine oxidase inhibition properties. Thus, these Sardinian honeys could have a great potential as antioxidant sources for pharmaceutical and cosmetic applications.