Combined electron capture and infrared multiphoton dissociation for multistage MS/MS in a Fourier transform ion cyclotron resonance mass spectrometer

We have mounted a permanent on-axis dispenser cathode electron source inside the magnet bore of a 9.4-T Fourier transform ion cyclotron resonance mass spectrometer. This configuration allows electron capture dissociation (ECD) to be performed reliably on a millisecond time scale. We have also implemented an off-axis laser geometry that enables simultaneous access to ECD and infrared multiphoton dissociation (IRMPD). Optimum performance of both fragmentation techniques is maintained. The analytical utility of performing either ECD or IRMPD on a given precursor ion population is demonstrated by structural characterization of several posttranslationally modified peptides: IRMPD of phosphorylated peptides results in few backbone (b- and y-type) cleavages, and product ion spectra are dominated by neutral loss of H3PO4. In contrast, ECD provides significantly more backbone (c- and z*-type) cleavages without loss of H3PO4. For N-glycosylated tryptic peptides, IRMPD causes extensive cleavage of the glycosidic bonds, providing structural information about the glycans. ECD cleaves all backbone bonds (except the N-terminal side of proline) in a 3-kDa glycopeptide with no saccharide loss. However, only a charge-reduced radical species and some side chain losses are observed following ECD of a 5-kDa glycopeptide from the same protein. An MS3 experiment involving IR laser irradiation of the charge-reduced species formed by electron capture results in extensive dissociation into c- and z-type fragment ions. Mass-selective external ion accumulation is essential for the structural characterization of these low-abundance (modified) peptides.

Antibacterial and cytotoxic effect of biologically synthesized silver nanoparticles using aqueous root extract of Erythrina indica lam

Simple, yet an effective and rapid approach for the green synthesis of silver nanoparticles (Ag NPs) using root extract of Erythrina indica and its in vitro antibacterial activity was tried against human pathogenic bacteria and its cytotoxic effect in breast and lung cancer cell lines has been demonstrated in this study. Various instrumental techniques were adopted to characterize the synthesized Ag NPs viz. UV-Vis (Ultra violet), FTIR (Fourier Transform Infrared), XRD (X-ray diffraction), DLS (Dynamic light scattering), HR TEM (High-resolution transmission electron microscopy), EDX (Energy-dispersive X-ray spectroscopy). Surface plasmon spectra for Ag NPs are centered nearly at 438 nm with dark brown color. FTIR analysis revealed the presence of terpenes, phenol, flavonols and tannin act as effective reducing and capping agents for converting silver nitrate to Ag NPs. The synthesized Ag NPs were found to be spherical in shape with size in the range of 20-118 nm. Moreover, the synthesized Ag NPs showed potent antibacterial activity against Gram positive and Gram negative bacteria and these biologically synthesized nanoparticles were also proved to exhibit excellent cytotoxic effect on breast and lung cancer cell lines.

Novel synthesis of heterocycles having a functionalized carbon center via nickel-mediated carboxylation: total synthesis of erythrocarine

Novel synthetic procedure of heterocycles was developed using nickel-mediated alkylative carboxylation, and the total synthesis of erythrocarine was achieved using this method and RCM of dienyne as the key steps. [reaction: see text]

Systematic comparison of oligosaccharide specificity of Ricinus communis agglutinin I and Erythrina lectins: a search by frontal affinity chromatography

Ricinus communis agglutinin I (RCA120) is considered a versatile tool for the detection of galactose-containing oligosaccharides. However, possible contamination by the highly toxic isolectin 'ricin' has become a critical issue for RCA120's continued use. From a practical viewpoint, it is necessary to find an effective substitute for RCA120. For this purpose, we examined by means of frontal affinity chromatography over 100 lectins which have similar sugar-binding specificities to that of RCA120. It was found that Erythrina cristagalli lectin (ECL) showed the closest similarity to RCA120. Both lectins prefer Gal beta1-4GlcNAc (type II) to Gal beta1-3GlcNAc (type I) structures, with increased affinity for highly branched N-acetyllactosamine-containing N-glycans. Their binding strength significantly decreased following modification of the 3-OH, 4-OH and 6-OH of the galactose moiety of the disaccharide, as well as the 3-OH of its N-acetylglucosamine residue. Several differences were also observed in the affinity of the two lectins for various other ligands, as well as effects of bisecting GlcNAc and terminal sialylation. Although six other Erythrina-derived lectins have been reported with different amino acid sequences, all showed quite similar profiles to that of ECL, and thus, to RCA120. Erythrina lectins can therefore serve as effective substitutes for RCA120, taking the above differences into consideration.

Anti-plasmodial flavonoids from the stem bark of Erythrina abyssinica

The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC(50) values of 7.9+/-1.1 and 5.3+/-0.7 microg/ml, respectively. From this extract, a new chalcone, 2',3,4,4'-tetrahydroxy-5-prenylchalcone (trivial name 5-prenylbutein) and a new flavanone, 4',7-dihydroxy-3'-methoxy-5'-prenylflavanone (trivial name, 5-deoxyabyssinin II) along with known flavonoids have been isolated as the anti-plasmodial principles. The structures were determined on the basis of spectroscopic evidence.

Facile and highly stereoselective synthesis of the tetracyclic erythrinane core

A highly stereoselective synthesis of the tetracyclic core of the Erythrina alkaloids is reported through the application of a Meyers bicyclic lactam template.

Synthesis of the tetracyclic framework of the erythrina alkaloids using a [4 + 2]-cycloaddition/Rh(I)-catalyzed cascade of 2-imidofurans

Several 2-imido substituted furans were found to undergo a rapid intramolecular [4 + 2]-cycloaddition to deliver oxabicyclo adducts in good to excellent yields. By using a Rh(I)-catalyzed ring opening of the resulting oxabicyclic adduct, it was possible to prepare several highly functionalized tetrahydro-1H-indol-2(3H)-one derivatives which were then used to prepare several erythrina alkaloids. By taking advantage of the Rh(I)-catalyzed reaction, it was possible to convert tert-butyl 3-oxo-5-carbomethoxy-10-oxa-2-azatricyclo[5.2.1.0(1,5)]dec-8-ene-2-carboxylate into the ring opened boronate by reaction with phenylboronic acid. Treatment of the boronate with pinacol/acetic acid afforded the corresponding diol which was used in a successful synthesis of racemic 3-demethoxyerythratidinone. During the course of these studies, several novel rearrangement reactions were encountered while attempting to induce an acid-initiated Pictet Spengler cyclization of a key lactam intermediate. The IMDAF/Rh(I)-catalyzed ring opening cascade sequence was also applied to the total synthesis of (+/-)-erysotramidine as well as the lycorine type alkaloid (+/-)-epi-zephyranthine.

Antimicrobial and radical scavenging flavonoids from the stem wood of Erythrina latissima

From the stem wood of Erythrina latissima, two isoflavones and a flavanone were isolated and characterized as 7,3'-dihydroxy-4'-methoxy-5'-(gamma,gamma-dimethylallyl)isoflavone (erylatissin A), 7,3'-dihydroxy-6'',6''-dimethyl-4'',5''-dehydropyrano [2'',3'': 4',5']isoflavone (erylatissin B), (-)-7,3'-dihydroxy-4'-methoxy-5'-(gamma,gamma-dimethylallyl)flavanone (erylatissin C), respectively, in addition to 10 known flavonoids. Structures of these compounds were determined on the basis of their spectroscopic data. These compounds showed antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Candida mycoderma. The isolated compounds also exhibited weak radical scavenging properties towards DPPH radical.

High-resolution crystal structures of Erythrina cristagalli lectin in complex with lactose and 2'-alpha-L-fucosyllactose and correlation with thermodynamic binding data

The primary sequence of Erythrina cristagalli lectin (ECL) was mapped by mass spectrometry, and the crystal structures of the lectin in complex with lactose and 2'-alpha-L-fucosyllactose were determined at 1.6A and 1.7A resolution, respectively. The two complexes were compared with the crystal structure of the closely related Erythrina corallodendron lectin (ECorL) in complex with lactose, with the crystal structure of the Ulex europaeus lectin II in complex with 2'-alpha-L-fucosyllactose, and with two modeled complexes of ECorL with 2'-alpha-L-fucosyl-N-acetyllactosamine. The molecular models are very similar to the crystal structure of ECL in complex with 2'-alpha-L-fucosyllactose with respect to the overall mode of binding, with the L-fucose fitting snugly into the cavity surrounded by Tyr106, Tyr108, Trp135 and Pro134 adjoining the primary combining site of the lectin. Marked differences were however noted between the models and the experimental structure in the network of hydrogen bonds and hydrophobic interactions holding the L-fucose in the combining site of the lectin, pointing to limitations of the modeling approach. In addition to the structural characterization of the ECL complexes, an effort was undertaken to correlate the structural data with thermodynamic data obtained from microcalorimetry, revealing the importance of the water network in the lectin combining site for carbohydrate binding.

General and Efficient Strategy for Erythrinan and Homoerythrinan Alkaloids: Syntheses of (±)-3-Demethoxyerythratidinone and (±)-Erysotramidine

[reaction: see text] A general and efficient strategy to both aromatic-type and nonaromatic-type erythrinan and homoerythrinan alkaloids has been developed. This approach involves a key two-step sequence, an alkylation of a ketone with various N-substituted iodoacetamides followed by a N-acyliminium ion promoted intramolecular cyclization, and represents one of the shortest routes to erythrinan and homoerythrinan alkaloids. As the application, the formal total synthesis of (+/-)-3-demethoxyerythratidinone and the total synthesis of (+/-)-erysotramidine have been achieved, respectively.

Protein tyrosine phosphatase-1B inhibitory activity of isoprenylated flavonoids isolated from Erythrina mildbraedii

Inhibition of protein tyrosine phosphatase-1B (PTP1B) has been proposed as a therapy for treatment of type-2 diabetes and obesity. Bioassay-guided fractionation of an EtOAc-soluble extract of the root bark of Erythrina mildbraedii, using an in vitro PTP1B inhibitory assay, resulted in the isolation of three new isoprenylated flavonoids, abyssinone-IV-4'-O-methyl ether (2), 7-hydroxy-4'-methoxy-3'-(3-hydroxy-3-methyl-trans-but-1-enyl)-5'-(3-methylbut-2-enyl)flavanone (3), and abyssinone-VI-4-O-methyl ether (6), along with six known flavonoids, abyssinone-V-4'-O-methyl ether (1), abyssinone-V (4), abyssinone-IV (5), sigmoidin E (7), 4'-hydroxy-5,7-dimethoxyisoflavone (8), and alpinumisoflavone (9). Compounds 1 and 2, 4-7, and 9 inhibited PTP1B activity, with IC50 values ranging from 14.8 +/- 1.1 to 39.7 +/- 2.5 microM. On the basis of the data obtained, flavanones and chalcones with isoprenyl groups may be considered as a new class of PTP1B inhibitors.

Mutational studies of the amino acid residues in the combining site of Erythrina corallodendron lectin

High-resolution X-ray crystallography of the complex of the Gal/GalNAc-specific Erythrina corallodendron lectin with lactose identified the amino acid side chains that form contacts with the galactose moiety of the disaccharide. The contribution of these amino acids to the binding of different monosaccharides and oligosaccharides by the lectin was examined by site-directed mutagenesis. Replacement of Phe131, on which the galactose is stacked, by tyrosine, gave a mutant with the same hemagglutinating activity and carbohydrate specificity as the parent lectin, but replacement by alanine or valine resulted in loss of activity. Mutations of Ala88, Asp89, and Asn133 produced mutants that were also inactive whereas those of the other combining site residues, Tyr106, Ala218, and Gln219, were biologically active. None of the active mutants interacted with mannose or glucose. Thus, contrary to an earlier assumption. Ala218 is not responsible for the inability of E. corallodendron lectin to bind these sugars. Our findings also demonstrate that Gln219 is not involved in galactose binding in solution, even though this is implicated by the crystal data. Instead, our data suggest that Gln219 assists in the ligation of N-acetyllactosamine to the lectin, by interacting with the acetamide group of the disaccharide. Comparison with other legume lectins specific for mannose/glucose, galactose, N-acetylgalactosamine, L-fucose or N-acetylglucosamine, shows that only three of the combining site residues of E. corallodendron lectin occupy invariant positions both in their primary and tertiary structures. These residues are an aspartic acid and an asparagine corresponding to positions 89 and 133, respectively, in E. corallodendron lectin, and an aromatic residue, either phenylalanine (as Phe131 in this lectin), tyrosine or tryptophan. We therefore postulate that these three residues are essential for ligand binding by all such lectins, irrespective of their specificity.

The anticancer potential of flavonoids isolated from the stem bark of Erythrina suberosa through induction of apoptosis and inhibition of STAT signaling pathway in human leukemia HL-60 cells

Erythrina suberosa is an ornamental tall tree found in India, Pakistan, Nepal, Bhutan, Burma, Thailand and Vietnam. We have isolated four known distinct metabolites designated as α-Hydroxyerysotrine, 4'-Methoxy licoflavanone (MLF), Alpinumisoflavone (AIF) and Wighteone. Among the four isolated metabolites the two flavonoids, MLF and AIF were found to be the most potent cytotoxic agent with IC50 of ∼20μM in human leukemia HL-60 cells. We are reporting first time the anticancer and apoptotic potential of MLF and AIF in HL-60 cells. Both MLF and AIF inhibited HL-60 cell proliferation and induce apoptosis as measured by several biological endpoints. MLF and AIF induce apoptosis bodies formation, enhanced annexinV-FITC binding of the cells, increased sub-G0 cell fraction, loss of mitochondrial membrane potential (Δψm), release of cytochrome c, Bax, activation of caspase-9, caspase-3 and PARP (poly ADP Ribose polymers) cleavage in HL-60 cells. MLF and AIF also increase the expression of apical death receptor, Fas, with inhibition of anti-apoptotic protein Bid. All the above parameters revealed that these two flavonoids induce apoptosis through both extrinsic and intrinsic apoptotic pathways in HL-60 cells. In spite of apoptosis, these two flavonoids significantly inhibit nuclear transcription factor NF-κB and STAT (Signal Transducer and Activator of Transcription) signaling pathway, which are highly expressed in leukemia. The present study provide an insight of molecular mechanism of cell death induced by MLF and AIF in HL-60 cells which may be useful in managing and treating leukemia.

Indicanines B and C, two isoflavonoid derivatives from the root bark of Erythrina indica

In addition to two known compounds, 5,4'-di-O-methylalpinumisoflavone and cajanin, a new 3-phenylcoumarin metabolite, named indicanine B, and a new isoflavone derivative, named indicanine C, were isolated from the root bark of Erythrina indica. By means of spectroscopic analysis, the structures of the new compounds were characterized as 4-hydroxy-3-(4'-hydroxyphenyl)-5-methoxy-2",2"-dimethylpyrano [5",6":6,7] coumarin and 4'-hydroxy-5-methoxy-2",2"-dimethylpyrano [5",6":6,7] isoflavone, respectively. The 13C-NMR data of cajanin and the in vitro antimicrobial spectrum and potencies of the isolated compounds are also reported.

Synthesis of the erythrina alkaloid 3-demethoxyerythratidinone. Novel acid-induced rearrangements of its precursors

[reaction: see text] A new strategy for the synthesis of 3-demethoxyerythratidinone has been developed and is based on an extraordinarily facile intramolecular Diels-Alder reaction of a 2-imido-substituted furan. During the course of the synthesis, several novel acid-induced rearrangement reactions were encountered.

Crystal structures of Erythrina cristagalli lectin with bound N-linked oligosaccharide and lactose

Erythrina cristagalli lectin (ECL) is a galactose-specific legume lectin. Although its biological function in the legume is unknown, ECL exhibits hemagglutinating activity in vitro and is mitogenic for T lymphocytes. In addition, it has been recently shown that ECL forms a novel conjugate when coupled to a catalytically active derivative of the type A neurotoxin from Clostridium botulinum, thus providing a therapeutic potential. ECL is biologically active as a dimer in which each protomer contains a functional carbohydrate-combining site. The crystal structure of native ECL was recently reported in complex with lactose and 2'-fucosyllactose. ECL protomers adopt the legume lectin fold but form non-canonical dimers via the handshake motif as was previously observed for Erythrina corallodendron lectin. Here we report the crystal structures of native and recombinant forms of the lectin in three new crystal forms, both unliganded and in complex with lactose. For the first time, the detailed structure of the glycosylated hexasaccharide for native ECL has been elucidated. The structure also shows that in the crystal lattice the glycosylation site and the carbohydrate binding site are involved in intermolecular contacts through water-mediated interactions.

Antibacterial pterocarpans from Erythrina subumbrans

Seven pterocarpans, erybraedin B (1), erybraedin A (2), phaseollin (3), erythrabyssin II (4), erystagallin A (5), erythrabissin-1 (6) and erycristagallin (7), two flavanones, 5-hydroxysophoranone (8) and glabrol (9), and one isoflavone, erysubin F (10), were isolated from the stems of Erythrina subumbrans (Leguminosae). Their structures were identified by means of spectroscopy. This is the first report of the isolation of the non-alkaloidal compounds from Erythrina subumbrans and the observed dehydration of 6a-hydroxypterocarpans 5 and 6 in CDCl(3) to the corresponding pterocarpenes 11 and 12, respectively. Compounds 8 and 9 were isolated for the first time from the genus Erythrina. Compounds 2 and 4 exhibited the highest degree of activity against Streptococcus strains with an MIC range of 0.78-1.56 microg/ml, whereas compound 7 exhibited the highest degree of activity against Staphylococcus strains, including drug-resistant strains (MRSA and VRSA), with an MIC range of 0.39-1.56 microg/ml. Interestingly, compounds 2, 4, 5 and 7 were more active against several strains of Streptococcus and Staphylococcus than the standard antibiotics vancomycin and oxacillin. Compound 7 showed the highest level of activity against all VRSA strains tested, with an MIC range of 0.39-1.56 microg/ml, which were resistant to both antibiotics. These compounds may prove to be potent phytochemical agents for antibacterial activity, especially against the MRSA and VRSA strains.

In vitro xanthine oxidase inhibitory activity of the fractions of Erythrina stricta Roxb

AIM OF THE STUDY

To assay the in vitro xanthine oxidase inhibitory activity of the various fractions of the hydromethanolic extract of the leaves of Erythrina stricta and to determine its enzyme inhibition mechanism.

MATERIALS AND METHODS

Xanthine oxidase inhibitory activity was assayed spectrophotometrically under aerobic conditions and the degree of enzyme inhibition was determined by measuring the increase in absorbance at 295 nm associated with uric acid formation. Enzyme kinetics was carried out using Lineweaver-Burk plots using xanthine as the substrate.

RESULTS

Among the fractions tested, the chloroform fraction exhibited highest potency (IC(50) 21.2+/-1.6 microg/ml) followed by the pet-ether (IC(50) 30.2+/-2.2 microg/ml), ethyl acetate (IC(50) 44.9+/-1.4 microg/ml) and residual (IC(50) 100+/-3.3 microg/ml) fractions. The IC(50) value of allopurinol used, as the standard was 6.1+/-0.3 microg/ml. Enzyme inhibition mechanism indicated that the mode of inhibition was of a mixed type.

CONCLUSION

These results suggest that the use of Erythrina stricta for the treatment of gout could be attributed to its xanthine oxidase inhibitory activity.

Erythrinaline alkaloids from the flowers and pods of Erythrina lysistemon and their DPPH radical scavenging properties

Fourteen different erythrinaline alkaloids have been isolated from the flowers and pods of Erythrina lysistemon with four being reported for the first time in nature and five for the first time in this species and the rest having been re-isolated. The new compounds are (+)-11beta-hydroxyerysotramidine (1), (+)-11beta-methoxyerysotramidine (2), (+)-11beta-hydroxyerysotrine N-oxide (4) and (+)-11beta-hydroxyerysotrine (8). (+)-11alpha-Hydroxyerysotrine N-oxide (3), earlier misidentified as erythrartine N-oxide (beta-hydroxyerysotrine N-oxide 4), was also re-isolated along with four other alkaloids. Correct identification of compounds 4 and 8 was aided by the fact that the two sets of C-11 epimers 3, 4 and 8, 9 were both isolated in this study thus making it easier to identify and assign the individual epimers. (+)-Erythristemine (14) was found distributed in most of the plant parts investigated. Preliminary work on the crude chloroform/methanol (1:1) showed moderate toxicity to brine shrimp (LC50 23 ppm) and moderate (IC50 86 microg/ml) radical scavenging properties against stable 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. The DPPH radical scavenging properties of the isolated compounds were assessed using TLC autographic and spectrophotometric assays whereupon only compounds 11 (1 microg; 90 microg/ml) and 12 (0.1 microg; 160 microg/ml) showed any notable activity. It appears the two compounds are slow reacting and do not reach steady state conditions within the standard half an hour time frame but only seemed to have reached steady state conditions after 4 h.

Differential affinities of Erythrina cristagalli lectin (ECL) toward monosaccharides and polyvalent mammalian structural units

Previous studies on the carbohydrate specificities of Erythrina cristagalli lectin (ECL) were mainly limited to analyzing the binding of oligo-antennary Galbeta1-->4GlcNAc (II). In this report, a wider range of recognition factors of ECL toward known mammalian ligands and glycans were examined by enzyme-linked lectinosorbent and inhibition assays, using natural polyvalent glycotopes, and a glycan array assay. From the results, it is shown that GalNAc was an active ligand, but its polyvalent structural units, in contrast to those of Gal, were poor inhibitors. Among soluble natural glycans tested for 50% molecular mass inhibition, Streptococcus pneumoniae type 14 capsular polysaccharide of polyvalent II was the most potent inhibitor; it was 2.1 x 10(4), 3.9 x 10(3) and 2.4 x 10(3) more active than Gal, tri-antennary II and monomeric II, respectively. Most type II-containing glycoproteins were also potent inhibitors, indicating that special polyvalent II and Galbeta1-related structures play critically important roles in lectin binding. Mapping all information available, it can be concluded that: [a] Galbeta1-->4GlcNAc (II) and some Galbeta1-related oligosaccharides, rather than GalNAc-related oligosaccharides, are the core structures for lectin binding; [b] their polyvalent II forms within macromolecules are a potent recognition force for ECL, while II monomer and oligo-antennary II forms play only a limited role in binding; [c] the shape of the lectin binding domains may correspond to a cavity type with Galbeta1-->4GlcNAc as the core binding site with additional one to four sugars subsites, and is most complementary to a linear trisaccharide, Galbeta1-->4GlcNAcbeta1-->6Gal. These analyses should facilitate the understanding of the binding function of ECL.

Role of N-linked glycan in the unfolding pathway of Erythrina corallodendron lectin

Erythrina corallodendron lectin (ECorL) exhibits an exquisitely structured oligosaccharide chain. Interestingly, the bacterially expressed, nonglycosylated counterpart, rECorL, possesses an essentially identical carbohydrate specificity and agglutinating activity as the glycosylated lectin, thus suggesting that the overall structure of the two are identical. This paper reports the unfolding behavior of E. corallodendron lectin in its glycosylated (EcorL) and nonglycosylated (rECorL) forms. ECorL shows a two-state unfolding pattern during isothermal melts and differential scanning calorimetry (DSC). The T(g) of ECorL as obtained from isothermal melts is 74 degrees C at pH 7.4. The T(p) obtained from DSC studies is between 74.8 to 68.1 degrees C in the pH range of 5.26-7.77. The recombinant lectin (rECorL), which is devoid of carbohydrate, shows, in contrast to the glycosylated protein, a non-two-state unfolding profile as measured by both probes mentioned, but the number of intermediates during unfolding could not be ascertained. Simulated annealing on ECorL, with the sugars removed, reveals that the protein Calpha backbones overlap, indicating that the overall structure, including the mode of dimerization, of rECorL is insignificantly altered as compared to ECorL. The alterations in the folding behavior of rECorL as compared to that observed in ECorL may be due to the fact that, unlike most other glycoproteins, one of the glycans in ECorL is unusually structured and forms many hydrogen bonds with the protein. It therefore appears that while the covalently linked sugar does not contribute appreciably to the final folded structure of ECorL, it does alter its folding process in a significant manner.

Anti-inflammatory activity of erycristagallin, a pterocarpene from Erythrina mildbraedii

Erycristagallin, a pterocarpene isolated from Erythrina mildbraedii, was tested in vitro for its antioxidant properties on the stable 2,2-diphenyl-1-pycryl-hydrazyl (DPPH) free radical and on the arachidonic acid metabolism. In addition, erycristagallin was tested on different experimental models of inflammation, such as the acute and chronic inflammation induced by the application of 12-O-tetradecanoylphorbol 13-acetate (TPA) on mice and the phospholipase A(2)-induced mouse paw oedema test. In the carrageenan-induced mouse paw oedema test, the ethyl acetate extract obtained from E. mildbraedii showed anti-inflammatory activity, and erycristagallin was isolated as the active principle. In vivo, erycristagallin significantly inhibited the phospholipase A(2)-induced mouse paw oedema as well as the mouse ear oedema induced by TPA (ID(50)<10 microg/ear). Moreover, it significantly reduced the chronic inflammation and leukocyte infiltration induced by repeated application of TPA. In vitro, erycristagallin inhibited the arachidonic acid metabolism via the 5-lipoxygenase pathway in rat polymorphonuclear leukocytes (IC(50)=23.4 microM), but had no effect on cyclooxygenase-1 metabolism in human platelets, while showing antioxidant activity in the DPPH test. As with other phenolics, the anti-inflammatory activity of erycristagallin may be based on its capacity to inhibit the arachidonic acid metabolism via the 5-lipoxygenase pathway.

New Protocols for the Assembly of the Tetracyclic Framework Associated with the Aromatic Erythrina Alkaloids

[reaction: see text] Treatment of the anion derived from the ring-fused gem-dichlorocyclopropane 4c with silver tetrafluoroborate afforded the spirocyclic compound 17 in 74% yield. Product 17 was readily converted, over three steps, into the beta-iodoethyl derivative 20 and treatment of this latter compound with n-Bu(3)SnH then afforded, in 93% yield and via a radical addition/elimination sequence, compound 2 incorporating the ABCD framework of the aromatic erythrina alkaloids.

Mn(III)/Cu(II)-mediated oxidative radical cyclization of alpha-(Methylthio)acetamides leading to erythrinanes

Treatment of N-[2-(3,4-dimethoxyphenyl)ethyl]-alpha-(methylthio)acetamide 3 with Mn(OAc)3 in the presence of Cu(OAc)2 gave tetrahydroindol-2-one 4, which then cyclized with Mn(OAc)3 to give 4-acetoxyerythrinane 5. A similar reaction of the 3,4-methylenedioxyphenyl congener 8 also gave tetrahydroindol-2-one 9, which, however, gave only a trace amount of the Mn(OAc)3-mediated cyclization product 11 and afforded the oxidation product 10. On the basis of these results, formation of 5 from 4 was thought to proceed via nucleophilic attack of the pyrrole ring on the cation-radical lX, generated by a single electron-transfer reaction of the acetoxy-substituted intermediate V. Treatment of compound 16 with Mn(OAc)3/Cu(OAc)2 gave no erythrinane derivative with recovery of the starting material, indicating that the presence of a methylthio group of 4 is essential for effecting the formation of erythrinane 5. On the other hand, treatment of 3 with Mn(OAc)3 using Cu(OTf)2 as an additive in place of Cu(OAc)2 gave another erythrinane 17. This method was applied to a formal synthesis of 3-demethoxyerythratidinone (20), a naturally occurring Erythrina alkaloid.

Flavonoids and isoflavonoids with antiplasmodial activities from the root bark of Erythrina abyssinica

From the root bark of Erythrina abyssinica a new pterocarpene [3-hydroxy-9-methoxy-10-(3,3-dimethylallyl)pterocarpene] and a new isoflav-3-ene [7,4'-dihydroxy-2',5'-dimethoxyisoflav-3-ene] were isolated. In addition, the known compounds erycristagallin, licoagrochalcone A, octacosyl ferulate and triacontyl 4-hydroxycinnamate were identified. The structures were determined on the basis of spectroscopic evidence. The crude extract and the flavonoids and isoflavonoids obtained from the roots of this plant showed antiplasmodial activities.