Phenylpropanoid glucosides from leaves of Coussarea hydrangeifolia (Rubiaceae)

Phenylpropanoid glycosides, 1 '-O-benzyl-alpha-(L)-rhamnopyranosyl-(1 ''-> 6 ')-beta-(D)-glucopyranoside (1) and alpha-(L)-Xylopyranosyl(4 '', 2 ')-(3-O-beta-(D)-glucopyranosyl)-1 '-O-E-caffeoyl-beta-(D)-glucopyranoside (2), together with the known derivatives, 1,6-di-O-caffeoyl- beta-(D)-glucopyrano side (3), 1-O-(E)-caffeoyl-beta-(D)-glucopyranoside (4) and 1-O-(E)-feruloyl-beta-(D)-glucopyranoside (5), were isolated from leaves of Coussarea hydrangeifolia. Their structures were determined by IR, HRESIMS, and I D and 2D NMR experiments, and their antioxidant activities, evaluated by assaying the free radical scavenging capacity using the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical as substrate. The antioxidant activities of 3 and 4 (IC50 values of 15.0 and 19.2 mu M, respectively) were comparable to that of the standard positive control caffeic acid, whilst 2 and 5 were only weakly active and 1 was inactive. (c) 2005 Elsevier Ltd. All rights reserved.

Supramolecular assemblies of cis-palladium complexes dominated by C-H center dot center dot center dot Cl interactions

Two cis-related palladium(II) complexes [PdCl(2)(PPh(3))(tu)] (1) and [PdCl(2)(tmen)] (2) {PPh(3) = triphenylphosphine, tu = thiourea, tmen = N,N,N,N-tetramethylethylenediamine} have been synthesized and characterized by elemental analysis, IR and NMR spectroscopies, and single crystal X-ray diffraction. In 1, N-H center dot center dot center dot Cl hydrogen bonds are responsible for the formation of a dimer which connects to an adjacent one through weak C-H center dot center dot center dot Cl interactions, yielding 1D tapes. The crystal packing of compound 2 consists of zigzag ribbons of [PdCl(2)(tmen)] self-assembled by C-H center dot center dot center dot Cl hydrogen bonds which also holds the chains together, giving rise to a 2D layered structure. (C) 2006 Elsevier B.V. All rights reserved.

Self-assembly of organometallic Pd(II) complexes via CH3 center dot center dot center dot pi interactions: the first example of a cyclopalladated compound with herringbone stacking pattern

Two binuclear cyclometallated compounds [Pd(C-2,N-dmba)(mu-N-3)](2) (1) and [Pd-2(C-2,N-dmba)(2)(mu-N-3)(mu-Cl)] (2) (dmba = N,N-dimethylbenzylarnine) have been synthesized and characterized by elemental 3 analysis, IR and NMR spectroscopies and single crystal X-ray diffraction crystallography. The ability of CH3 groups to form C(sp(3))-H...pi hydrogen bonds with phenyl rings is responsible for the molecular self-assembly within the crystals of 1 and 2. Compound 1 crystallizes as one-dimensional supramolecular chains whereas the crystal packing of 2 consists of a herringbone of sandwiches composed by two inversely related [Pd-2(C-2,N-dmba)(2)(mu-N-3)(mu-Cl)] molecules. (c) 2007 Elsevier B.V. All rights reserved.

Phospholipase A(2) - A structural review

Phospholipases A(2) (PLA(2)) are widely distributed in nature and are well characterized proteins with respect to their catalytic and pharmacological activities, A wealth of structural information has recently become available both from X-ray diffraction and NMR studies, and although a detailed model of the catalytic mechanism of PLA(2) has been proposed, the structural bases of other aspects of PLA(2) function, such as interfacial activation and venom PLA(2) pharmacological activities, are still under debate. An appreciation of the PLA(2) protein structure will yield new insights with regard to these activities, the salient structural features of the class I, II and III PLA(2) are discussed with respect to their functional roles. Copyright (C) 1996 Published by Elsevier B.V. Ltd

Novel stereoselective addition of some nucleophiles to 2,3-bis(methylsulfanyl) norbornenobenzoquinone

2,3-Bis(methylsulfanyl)norbomenobenzoquinone undergoes reaction with nitrogen, oxygen, sulfur or carbon nucleophiles to give the trisubstituted adducts containing the new substituent at the ring junction. Their configurations are assigned by H-1 NMR spectroscopy and NOE enhancement experiments. (C) 1997 Elsevier B.V. Ltd.

Antioxidant quinonemethide triterpenes from Salacia campestris

A new quinonemethide triterpene named as salacin, has been isolated from the root bark of Salacia campestris in addition to the known pristimerin, maytenin, 20 alpha-hydroxymaytenin, and netzahualcoyene. Salacin was identified on the basis of NMR-spectral and mass spectrometric analysis. The free-radical scavenging activities of the quinonemethide triterpenes salacin (1), pristimerin (2), maytenin (3), 20a-hydroxymaytenin (4), and netzahualcoyene (5) towards DPPH have been evaluated and showed absorbance variation (AA) of 19, 20, 39, 28, 55, and 10%, respectively, having rutin (74% at 50 pm) and BHT (7% at 50 mu M) as standard compounds.

Structure of a glycoglucuronomannan from the low-viscosity gum of Vochysia lehmannii

The polysaccharide (VSP) from the gum exudate of quaruba (Vochysia lehmannii) had two components of almost identical M. centred at 24,800, as shown by HSPEC-MALLS. The presence of aggregates was shown since carboxy-reduction gave VSP-RED, which contained low molecular weight components with M-w 19,000 > 5800 and polydispersity ratios dn/dc 0.160 and 0.149, respectively. VSP formed low viscosity aqueous solutions and acid hydrolysis gave Man (30%), Ara (16%), Gal (10%), and Glc (14%). The latter arose partly from GlcA (30%). Methylation analysis revealed mainly neutral units of 2-O- (60%) and 2,3-di-O-substituted Manp (5%), and those of nomeducing ends (8%), 2-O- (3%), and 4-O-substituted Arap and/or 5-O-substituted Araf units (6%). VSP-RED contained Glc (45%), Man (35%), and Ara (13%) and methylation analysis indicated mainly 4-O-substituted Glcp (31%) and 2-O- (51%) and 2,3-di-O-substituted Manp units (5%). A predominant alternating structure for VSP was shown by its C-13 NMR spectrum, which contained 10 main signals and a small one of C-6 of GlcpA. This was confirmed by formation, on partial hydrolysis of VSP, of a tetrasaccharide, which was characterised by NMR spectroscopy and ESI-MS as beta-GlcpA-(1 --> 2)-alpha-Manp-(1 --> 4)-beta-GlcpA-(1 --> 2)-Man, which arose from the main chain, thus confirming VSP to be a glycoglucuronomannan. (C) 2004 Elsevier Ltd. All rights reserved.

Preparative isolation of a novel flavonoid from an infusion of Byrsonima basiloba leaves by high-speed counter-current chromatography

A method for the isolation of three compounds from the infusion of leaves of Byrsonima basiloba A. Juss. by high-speed counter-current chromatography (HSCCC) was developed. This technique led to the separation of a novel compound, quercetin 3-O-alpha-L-rhamnopyranosyl-(1 -> 3)-O-[alpha-L-rhamnopyranosyl-(1 -> 6)]-beta-D-allopyranoside, and two known compounds quercetin3-O-(X-L-rhamnopyranosyl-(1 -> 6)-beta-D-galactopyranoside and (+)-catechin in 4 h with purities of over 92%. The structures of the compounds were determined by one- and two-dimensional NMR spectroscopy and HPLC.

Structural characterization of the cell wall D-glucans isolated from the mycelium of Botryosphaeria rhodina MAMB-05

Three D-glucans were isolated from the mycelium of the fungus Botryosphaeria rhodina MAMB-05 by sequential extraction with hot-water and hot aqueous KOH (2% w/v) followed by ethanol precipitation. Following their purification by gel permeation chrornatography on Sepharose CL-4B, the structural characteristics of the D-glucans were determined by FT-IR and C-13 NMR spectroscopy and, after methylation, by GC-MS. The hot-water extract produced a fraction designated Q(1A) that was a beta-(1 -> 6)-D-glucan with the following structure:[GRAPHICS]The alkaline extract, when subjected to repeated freeze-thawing, yielded two fractions: KIP (insoluble) that comprised a beta-(1 -> 3)-D-glucan with beta-D-glucose branches at C-6 with the structure:[GRAPHICS]and K1SA (soluble) consisting of a backbone chain of alpha-(1 -> 4)-linked D-glucopyranosyl residues substituted at O-6 with alpha-D-glucopyranosyl residues:[GRAPHICS](c) 2008 Elsevier Ltd. All rights reserved.

First record of L-quebrachitol in Allophylus edulis (Sapindaceae)

Allophylus edulis, commonly called 'Chal chal', is a member of the Sapindaceae occurring in the Uruguayan and Brazilian native flora. During the phytochemical analysis of two Chal chal specimens from two welldifferentiated geographical zones (Assis, São Paulo, Brazil, and Santa Lucia, Canelones, Uruguay), considerable amounts of L-quebrachitol were isolated from both samples. The isolation was carried out from the ethanolic twig extracts obtained by maceration of both vegetal samples. White easily distinguishable crystals were mechanically separated, washed, and characterized by 1D and 2D NMR experiments and by MS data. Such techniques confirmed that the crystals isolated from sources collected in both countries resulted in the same compound, L-quebrachitol, a natural product not previously reported for this species and one that has been investigated as a sugar substitute for diabetics. Worthy of note, the content of L-quebrachitol in A. edulis may be the chemical basis to explain its ethnobotanical uses, since infusions of this plant are used to treat diabetes in the practice of local traditional medicine. (c) 2008 Elsevier Ltd. All rights reserved.

Physico-chemical parameter correlations in the [RuCl2(CO)(L)(PPh3)2] complexes (L = N-heterocycles)

Fourteen complexes in the series [RuCl2(CO)(L)(PPh3)2] (where L = N-heterocycles) have been prepared and characterized by IR and NMR spectroscopies, and cyclic voltammetry. A good correlation is found between observed and calculated electrochemical potentials; E1/2 vs pKa or (Gp, σm for a series of similar ligands. It is now reported that the carbonyl stretching frequency, νCO, and the 13C and 31P NMR signals do not correlate well with any of the physico-chemical parameters used (E1/2, Taft's and Hammett's parameters). This behaviour is probably due to the characteristics of the Ru(II) species, which does not transmit the steric and electron donor/acceptor properties of the ligands to the carbonyl group, or because the measurements are not able to detect the effect induced by the changes in the ligand L. Indeed, good correlations are obtained when the measurements directly involve the metal centre, as is the case in the E1/2 measurements. Crystals of o[RuCl2(CO)(4-pic)(PPh3)2] are monoclinic, space group P21/n, a = 12.019(2), b = 13.825(3) and c = 22.253(3) . The structure was solved by the Patterson method and was refined by full-matrix least-squares procedure to R = 0.054 and Rw = 0.055, for 2114 reflections with I > 3σ(I). For L = 2-acetylpyridine and 2-methylimidazole, complexes with formulae [RuCl2(CO)(L)(PPh3)] · L and [RuCl2(CO)(L)2 (PPh3)], respectively, were obtained. © 1998 Elsevier Science Ltd. All rights reserved.

Saponinas triterpênicas de Tocoyena brasiliensis Mart. (Rubiaceae)

The present communication reports the isolation and identification of four triterpenoid saponins from the chloroform extract of the leaves of Tocoyena brasiliensis: 3-O-β-D-quinovopyranosyl quinovic acid, 3-O-β-D- quinovopyranosyl cincholic acid, 3-O-β-D-glucopyranosyl quinovic acid and the 28-O-β-D-glucopyranosyl ester derivative of quinovic acid as binary mixtures, respectively. From the ethanol extract a flavonoid identified as ramnazin-3-O-rutinoside was obtained. The structures of these compounds were assigned by data analysis of ID and 2D NMR spectrometry and comparison with data recorded in the literature for these compounds.

New bioactive metabolites produced by Phomopsis cassiae, an endophytic fungus in Cassia spectabilis

Two new metabolites, ethyl 2,4-dihydroxy-5,6-dimethylbenzoate (1) and phomopsilactone (2) were isolated from Phomopsis cassiae, an endophytic fungus in Cassia spectabilis. Their structures were elucidated by 1D and 2D NMR, MS and IR spectral data. Compounds 1 and 2 displayed strong antifungal activity against the phytopatogenic fungi Cladosporium cladosporioides and C. sphaerospermum, as well as cytotoxicity against human cervical tumor cell line (HeLa), in in vitro assays. ©2005 Sociedade Brasileira de Química.

A new ent-kaurane diterpene from stems of Alibertia macrophylla K. Schum. (Rubiaceae)

Phytochemical investigations of the stems of a specimen of Alibertia macrophylla led to the isolation and characterization of the new diterpene ent-kaurane-2β,3α,16α-triol (1), along with triterpenes 2-8, iridoids 9-12, and phenolic acids 13-15. The structure of 1 was established based on spectroscopic studies (1H- and 13C-NMR, IR, and HR-ESI-MS). This is the first report of the isolation of a diterpene from the Alibertia genus in Rubiaceae. © 2007 Verlag Helvetica Chimica Acta AG.

Flavonóides de Calotropis procera R. Br. (Asclepiadaceae)

In this work we report the identification of two flavonol glycosides isolated from the leaves of Calotropis procera R. Br. (Asclepiadaceae), a plant species with large occurrence in Northwest of Brazil with some applications in folk medicine. Some proved pharmacological activities in this species could be attributed to the presence of flavonol glycosides. The extraction and isolation of flavonol glycosides was carried out firstly by a liquid-liquid partition, and then by elution of n-BuOH fraction with MeOH over a Sephadex LH-20 column. The identification of flavonol glycosides isorhamnetin-3-O-rutinoside (1), and isorhamnetin-3-O-robinobioside (2), was obtained by 1H and 13C NMR, one- and two-dimensional techniques.