Rute Cunha Figueiredo

Chemical constituents of Salacia elliptica (Celastraceae)

The chemical investigation of Salacia elliptica allowed to the isolation of 20 constituents: two polyols, one xanthone, a mixture of long chain hydrocarbons, one carboxylic acid, one polymer, two steroidal compounds, one aromatic ester and eleven pentacyclic triterpenes. These triterpenes include 3β-stearyloxy-oleanane, 3β-stearyloxy-ursane, one seco-friedelane, and eight compounds of the friedelane serie. The chemical structure and the relative configuration of a new triterpene 1,3-dioxo-16α-hydroxyfriedelane (15) were established through 1H and 13C NMR including 2D experiments (HMBC, HMQC, COSY and NOESY) and herein reported for the first time.

Triterpenes from Maytenus gonoclada and their attractive effects on Tenebrio molitor

Bioactive metabolites have been isolated from plants of the genus Maytenus (Celastraceae), such as maytansinoids with insecticide activity, sesquiterpene pyridine alkaloids with insect antifeedant activity, and nortriterpene quinonemethides, which show antimicrobial activity [1]. Despite the great diversity of plant metabolites showing several biological activities, no compound with the friedelane skeleton presenting attractive-repellent effects has been described until now [2]. Previous phytochemical studies with aerial parts of Brazilian Maytenus species showed mainly pentacyclic triterpenes (PCTT) of the friedelane series, which are regarded as the characteristic constituents of plants belonging to this genus. It is worth noting that the PCTT were identified as the principal constituents of some Brazilian Maytenus sp. Maytenus gonoclada Martius (Celastraceae), which can be found in the “cerrado” region and rupestrian fields of Southeast and Northeastern Brazil. It is a polymorphic tree, usually spiny, the spines sometimes end in short shoots. The leaves alternate and are extipulate. The flowers are hermaphrodite in axillary, solitary, or fascicled dichotomous cymes; the calix is 4-5-lobed. The petals are 4–5, spreading. The stamens are 4–5, inserted on the margin of the disc or slightly below it; the filaments are slender and broad [3]. In this work we report the isolation, from the aerial parts of M. gonoclada, of seven compounds of the friedelane series: 3-oxofriedelane (1) [4], 3 -hydroxyfriedelane (2) [5], 3,11-dioxofriedelane (3), 3,16-dioxofriedelane (4) [6], 3-oxo-12 -hydroxyfriedelane (5) [7], 3-oxo-28-hydroxyfriedelane (6) [8], and 3-oxo-29-hydroxyfriedelane (7) [9]; two members of the lupane series, 3 -stearyloxy-lup-20(29)-ene (8) and lupeol (9) [10]; a taraxane, 3 -taraxerol (10) [11]; two ursanes, -amyrin (11) [6] and 3 -stearyloxy-urs-12-ene (12) [12]; and oleanane -amyrin (13) [13]. -Sitosterol (14) [14], the polyol dulcitol or galactitol (15) [15], and palmitic acid (16) [16] were also chemically characterized. Two long-chain hydrocarbons with 28 and 36 carbons, respectively (17), were identified through high-resolution gas chromatography (GC). The hexane extract and constituents of M. gonoclada were tested for their attractive-repellent effects on the larvae of Tenebrio molitor (L.) (Coleoptera: Tenebrionidae). The hexane extract, the mixture of 3,11-dioxofriedelane and 3,16-dioxofriedelane, and the terpene 3-oxo12 -hydroxyfriedelane showed attractive effects on these larvae. Phytochemical studies demonstrated that the aerial parts of Brazilian Maytenus species consist mainly of triterpenes of the friedelane series, which are regarded as the characteristic constituents of plants belonging to this genus [2, 17]. It is worth noting that the pentacyclic triterpenes were identified as the principal constituents of Brazilian Maytenus sp. In the present work, we report the isolation of 13 known pentacyclic triterpenes: seven friedelanes (1–7), two lupanes (8 and 9), one taraxane (10), two ursanes (11 and 12), and the oleanane (13) obtained from M. gonoclada. Compounds 1 to 13 give a Liebermann–Buchard (LB) positive test for pentacyclic triterpenes, and 14 for steroids [18]. The 1H NMR spectra of constituents 1–7 showed a hydrogen signal at ~ H 0.87 (d, J = 6.8 Hz), which is in accord with the C-23 methyl group of members of the friedelane series. The 13C NMR data confirmed that compounds 1–7 are friedelane derivatives [6]. The 1H NMR spectra of compounds 8 and 9 showed signals at H 4.6 and H 4.7 that are characteristics of lupane triterpenes [19]. The presence of signals at C 150.98 and C 109.36 observed in 13C NMR spectra confirmed the lupane skeleton of these compounds [10].

Maytenus salicifolia Reissek, Celastraceae: triterpenes isolated from stems and antioxidant property of extracts from aerial parts

Six pentacyclic triterpenes were isolated from hexane extract of stems of Maytenus salicifolia Reissek, Celastraceae: 30-hydroxyfriedelan-3-one (1), 3,16-dioxofriedelane (2), friedeline (3), lupeol (4), betuline (5) and lup-20(29)-en-3,30-diol (6). The structure each one was established on the basis of detailed 1H and 13C NMR spectral investigation and by comparison with the respective literature values. For compound 1, the complete 2D NMR (HMBC, HMQC and NOESY) spectral data were herein reported for the first time. Compounds 1, 2, 5 and 6 were isolated for the first time from this plant. Antioxidant activity is described for some extracts from species of the Celastraceae family, then, the extracts from aerial parts of M. salicifolia were evaluated in relation to antioxidant potential using the DPPH method. Compared to quecertin, the AcEt extract (EAF) from leaves, AcEt (EAPF) and MeOH (EMPF) from pulp fruit and AcEt (EAT) and MeOH (EMT) from stems showed significant antioxidant property.

Síntese de amidas e sulfonamidas de beta-D-galactopiranosilamina e beta-lactosilamina e avaliação de suas interações com lectinas de Erythrina cristagalli e de Ricinus communis

We report herein the synthesis of some b-D-galactopyranosylamine and b-lactosylamine amides and sulfonamides. The interactions of these compounds with lectins from the seeds of Erythrina cristagalli (LEC) and Ricinus communis (RCA120) were evaluated in a hemagglutination inhibitory activity assay. D-Galactose and lactose were used as reference compounds. The b-lactosylamine amides and sulfonamides were nearly as active as lactose in inhibiting LEC mediated hemagglutination and were less active against RCA120 agglutinin. The b-D-galactopyranosylamine amides and sulfonamides were, with one exception, considerably less active than D-galactose in the assay with both lectins.

Detection of glycidic receptors in microalgae using glycodendrons as probes: a new tool for studies on cell surface interactions

Cell recognition, adhesion, and internalization are involved in infectious, reproductive, and inflammatory processes and are generally mediated by interactions between molecules located in the cell membrane and the extracellular matrix. These processes can decrease proliferation rates and they are well known for bacteria, fungi, and animals, but there is a lack of knowledge regarding autotrophic cells. Carbohydrates and proteins (e.g., lectins) are important molecules for cell interactions and information about these molecules is essential to better understand many biological phenomena in uni- or multicellular organisms. Most studies focus on the identification of the carbohydrates present on the cell surface by using labeled lectins. Alternatively, here we present a pioneer research performed by using three different labeled carbohydrates in a multivalent presentation (glycodendrons) to detect the presence of carbohydrate receptors (e.g., lectins) on cell surfaces of 12 algal species. The goal of this study was to detect some specificity in these molecular interactions, but in a reverse way in comparison to that commonly described in the literature. We tested trivalent molecules containing residuals of D-mannose, L-fucose, or N-acetyl-galactosamine to identify their bindings with the corresponding lectins expressed on cell surfaces. We envisage that our new approach could be an alternative tool for taxonomic and physiological studies on microalgae or even on other groups of organisms. Based on our results, the receptors found in the cell surface of the algal species tend to differ in composition, quantity, and distribution. The differences were mainly species-specific, since no patterns were identified at higher taxonomic level. Moreover, like lectins, labeled carbohydrates were proved to be a reliable tool for the study of cell surface composition.

Síntese de β-D-galactopiranosídeos de arila diméricos para avaliação de sua interação com a lectina de Erythrina cristagalli

WITH THE Erythrina cristagalli LECTIN. The synthesis of two new D-galactose-based dimers having a 1,4-butanediamine spacer is reported aiming at the evaluation of their interaction with the Erythrina cristagalli lectin. The title compounds were prepared in four and five steps from 2,3,4,6-tetra- O-acetyl-b-D-galactopyranoside bromide, in 20 % and 15 % overall yield, respectively, using the Doebner modification of the Koenavenagel reaction as the key sep. The lectin-carbohydrate interaction could be evaluated for only one dimer, due to solubility problems. A twofold enhancement of affinity was observed, compared to the corresponding monovalent ligand.

Síntese de beta-N-acetilglicosaminídeos de arila modificados em C-6 como potenciais agentes antimicrobianos

We report herein the synthesis of aryl b-N-acetylglucosaminides containing azido, amino and acetamido groups at C-6 as potential antimicrobial agents. It was expected that these compounds could interfere with the biosynthesis and/or biotransformation of N-acetylglucosamine in fungi and bacteria. None of the compounds showed antimicrobial activity against bacteria (Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa), filamentous fungus (Aspergillus niger) and yeasts (Saccharomyces cerevisae, Candida albicans and Candida tropicallis), at the concentration of 1 mg/mL in agar diffusion assay.