Natural and Enantiopure Alkylglycerols as Antibiofilms Against Clinical Bacterial Isolates and Quorum Sensing Inhibitors of Chromobacterium violaceum ATCC 12472.

Resistance mechanisms occur in almost all clinical bacterial isolates and represent one of the most worrisome health problems worldwide. Bacteria can form biofilms and communicate through quorum sensing (QS), which allow them to develop resistance against conventional antibiotics. Thus, new therapeutic candidates are sought. We focus on alkylglycerols (AKGs) because of their recently discovered quorum sensing inhibition (QSI) ability and antibiofilm potential. Fifteen natural enantiopure AKGs were tested to determine their effect on the biofilm formation of other clinical bacterial isolates, two reference strains and their QSI was determined using Chromobacterium violaceum ATCC 12472. The highest biofilm inhibition rates (%) and minimum QS inhibitory concentration were determined by a microtiter plate assay and ciprofloxacin was used as the standard antibiotic. At subinhibitory concentrations, each AKG reduced biofilm formation in a concentration-dependent manner against seven bacterial isolates, with values up to 97.2%. Each AKG displayed QSI at different levels of ability without affecting the growth of C. violaceum. AKG (2S)-3-O-(cis-13'-docosenyl)-1,2-propanediol was the best QS inhibitor (20 µM), while (2S)-3-O-(cis-9'-hexadecenyl)-1,2-propanediol was the least effective (795 µM). The results showed for the first time the QSI activity of this natural AKG series and suggest that AKGs could be promising candidates for further studies on preventing antimicrobial resistance.

Enantiomeric synthesis of natural alkylglycerols and their antibacterial and antibiofilm activities.

Alkylglycerols (AKGs) are bioactive natural compounds that vary by alkyl chain length and degree of unsaturation, and their absolute configuration is 2S. Three AKGs (5l-5n) were synthesised in enantiomerically pure form, and were characterised for the first time together with 12 other known and naturally occurring AKGs (5a-5k, 5o). Their structures were established using 1H and 13C APT NMR with 2D-NMR, ESI-MS or HRESI-MS and optical rotation data, and they were tested for their antibacterial and antibiofilm activities. AKGs 5a-5m and 5o showed activity against five clinical isolates and P. aeruginosa ATCC 15442, with MIC values in the range of 15-125 µg/mL. In addition, at half of the MIC, most of the AKGs reduced S. aureus biofilm formation in the range of 23%-99% and P. aeruginosa ATCC 15442 biofilm formation in the range of 14%-64%. The antibiofilm activity of the AKGs assessed in this work had not previously been studied.

Flavonols and sesquiterpenoids from outer bark and leaves of Croton polycarpus Benth. (Euphorbiaceae) / Flavonoles y sesquiterpenoides de la corteza y hojas de Croton polycarpus Benth. (Euphorbiaceae)

Some known flavonols from the outer bark polar fraction of the native species Croton polycarpus Benth. (Euphorbiaceae) were isolated and quercetin, quercitrin and rutin were identified as the most abundant constituents. From this sample, a clean TLC non polar sub- fraction (A-1) obtained by CC, afforded several isomeric compounds, which were characterized by GC-MS/EI and its results conduct to a group of eighteen sesquiterpenoids with a unique Rf value in TLC; among them, one sesquiterpene hydrocarbon with molecular weight (MW) of 200 g/mol (C15H20), two with MW 202 g/mol,(C15H22), thirteen with a MW of 204 g/mol (C15H24) and two sesquiterpenols with MW 220 g/mol (C15H24O) were determined. From its fresh leaves essential oil obtained by two methods, hydro-distillation and supercritical CO2 extraction, other terpenoids were identified, where the first one process was more efficient (1.5% DM yield) than the last one, and it was selected for a pilot study. This is the first report about chemical composition of the native species C. polycarpus, and the analysis of sesquiterpene isomerism is very important to recognize its structural diversity and similar chemical behavior.

De la fracción polar de la corteza de la especie nativa Croton polycarpus, (Euphorbiaceae) se separaron algunos flavonoles y quercetina, quercitrina y rutina se identificaron como los constituyentes más abundantes. Desde una fracción apolar de esta muestra, se obtuvo por CC una fracción limpia en CCD (C-2), cuyo fraccionamiento por análisis por CGAR-EM/IE permitió determinar un grupo de 18 sesquiterpenoides mayoritarios los cuales presentan un valor único de Rf; entre estos se detectó un hidrocarburo de PM 200 (C15H20), dos derivados de PM 202 (C15H22), trece son hidrocarburos isómeros con PM 204 g/mol (C15H24) y dos terpenoles de PM 220 uma (C15H24O). De igual forma, de las hojas frescas se extrajo el aceite esencial, por dos métodos: hidrodestilación y extracción con CO2 supercrítico (SFE), y el primero de ellos fue el más eficiente (1,5% rendimiento en peso seco) por lo cual se seleccionó para el desarrollo de experimentos a escala de planta piloto. Este informe es la primera contribución al conocimiento de la composición química y la bioactividad de las hojas y corteza de la especie arbórea nativa Croton polycarpus (Euphorbiaceae) y el análisis de mezclas de sesquiterpenos isómericos es muy importante para reconocer la diversidad estructural y su similitud en polaridad y comportamiento químico.

Two new secoiridoids from Chelonanthus alatus (Aubl) Pulle (Gentianaceae) / Dos nuevos secoiridoides de Chelonanthus alatus (Aubl) Pulle (Gentianaceae)

The species Chelananthus alatus is an herbaceous plant with known ethno botanical and medicinal properties used in control of fever, especially those produced by malaria. From dried leaves (1.11 Kg), the crude alcoholic extract was fractionated by liquid-liquid partition with different polarity solvents. From the sec-butyl alcohol soluble fraction, by successive application of chromatographic methods, four compounds type iridoid were isolated and identified by spectroscopic techniques. Compound 1 is a new secoiridoid which was identified as sweroside 7-isobutyryloxy, and it is reported here for the first time in the Gentianaceae family; the other secoiridoids which were isolated are known as vogeloside (2), dihydro-chelonanthoside (3) and sweroside (4); vogeloside was identified for the first time in this plant (C. alatus). From the isopropyl acetate extract, in conjunction with the sweroside 7- isobutyryloxy (1), chelonanthoside (5) and sweroside (4), were identified, along with the sweroside 7-isovaleryloxy-(6) as a new side chain isomeric ester of dihydrochelonanthoside (3) . This work presents the spectroscopic analysis of the new structures and some bioactivity data.

La especie Chelonanthus alatus (Gentianaceae) es una hierba de aplicaciones ethnobotánicas reconocidas en medicina tradicional, especialmente en el control de la fiebre producida por la malaria. De las hojas secas (1,11 Kg) se realizó el extracto crudo en alcohol etílico, el cual se fraccionó por partición líquido-líquido (L-L) con disolventes de diferente polaridad. De la fracción soluble en alcohol sec-butílico, se aislaron cuatro compuestos tipo seco-iridoide por aplicación sucesiva de diversos métodos cromatográficos los cuales se identificaron por técnicas espectroscópicas. El compuesto 1 es un nuevo secoiridoide identificado como de 7- isobutiriloxi-swerosido, y se reporta por primera vez en la familia Gentianaceae; los otros tres secoiridoides aislados se conocen como vogelósido (2), dihidrochelonanthosido (3) y swerósido (4); el vogelósido se identificó por primera vez en C. alatus. De la fracción soluble en acetato de isopropilo además del 7-isobutiriloxi-swerosido (1) y el swerosido se aislaron e identificaron, el chelonanthosido (5) y el isovaleriloxi-swerosido (6), el cual es un nuevo isómero del dihidrochelonanthosido. En este trabajo se presenta el análisis espectroscópico que llevó a la elucidación estructural de los compuestos novedosos y algunos datos de bioactividad.

Cassipourol: un diterpenoide monocíclico con actividad larvicida en Croton funckianus / Cassipourol: a monocyclic diterpenoid with larvicidal activity from Croton funckianus

Bioassay-guided fractionation of petroleum ether soluble part of the ethanolic extract of Croton funckianus (Euphorbiaceae: Crotonoideae) senescent leaves against Culex quinquefasciatus third instar larvae afforded a diterpenoid with Larvicidal activity called cassipourol. The structure of cassipourol was elucidated by 1D (1H, 13C) and 2D (COSY, HMQC, HMBC) NMR spectroscopy and by comparing their spectroscopic data with that reported in the literature.

El fraccionamiento guiado por bioensayos de la fracción soluble en éter de petróleo del extracto etanólico proveniente de las hojas senescentes de la especie Croton funckianus (Euphorbiaceae: Crotonoideae) frente a larvas de tercer estadio del mosquito zancudo Culex quinquefasciatus condujo a la identificación de un nuevo diterpenoide con actividad larvicida denominado cassipourol. La estructura del cassipourol se elucido empleando espectroscopia RMN 1D (1H, 13C) y 2D (COSY, HMQC, HMBC) y por comparación de sus datos espectroscópicos con los reportados en la literatura.

Essential oil from leaves of Lippia dulcis grown in Colombia.

The chemical composition of the volatile compounds from the leaves of Lippia dulcis Trev. (Verbenaceae) from Colombia was studied by GC and GC/MS. Forty volatile compounds were identified, of which the major ones were alpha-copaene (18.0%), beta-caryophyllene (17.8%), and delta-cadinene (14.7%). The sweet bisabolane sesquiterpenoid, hernandulcin, formed only 1.1% of the leaf oil.

3-O-a-L-RAMNOPIRANOSILFLAVONOIDES Y OTROS DERIVADOS FENÓLICOS DE HOJAS DE Calliandra calothyrsus. MEISSNER (MIMOSACEAE) / 3-O-a-L- RHAMNOPYRANOSILFLAVONOIDS AND OTHER PHENOLICS COMPOUNDS FROM Calliandra calothyrsus. MEISSNER LEAVES (MIMOSACEAE) / 3-O-a-L-RAMNOPIRANOSILFLAVONOIDES E OUTROS DERIVADOS FENÓLICOS DE FOLHAS DE Calothyrsus de Calliandra. MEISSNER (MIMOSACEAE)

El estudio químico del extracto polar de hojas de Calliandra calothyrsus.Meissner (Mimosaceae) (accesión CIAT 22316) condujo a la identificación de dos flavonoides glicosilados: 3-O-a-L-ramnopiranosil- 7-metoxi-5,3’,4’-trihidroxiflavona y 3-O-a-L-ramnopiranosil-5,7, 3’,4’-tetrahidroxiflavona; sus estructuras fueron elucidadas por métodos espectroscópicos IR y RMN (1D y 2D). Adicionalmente, por espectrometría de masas por las técnicas DART y ESI de alta resolución, se identificaron derivados fenólicos mayoritarios, tales como ácido gálico y su dímero (PM 339,032), dihidroxicumarina, trihidroxicumarina, quercetina, dihidroquercetina, 3-O-a-Lramnopiranosil- 7-metoxi-5,3’,4’-trihidroxiflavona, 3-O-a-ramnopiranosil- 5,7,3’,4’-tetrahidroxiflavona y un dímero de flavonoide como principales constituyentes químicos.

Chemical investigation of the polar extract from Calliandra calothyrsus. Meissner (Mimosaceae) (accession CIAT 22316) leaves, afforded two known glycosylflavonoids: 3-O-a-L-rhamnopiranosyl-7-metoxi-5,3’,4’-trihydroxyflavone and 3-O-a-L-rhamnopiranosyl -5,7, 3’,4’-tetrahydroxyflavone; their chemical identities were established by IR and 1D and 2D-NMR experiments. Furthermore gallic acid, dihydroxycumarine, trihydroxycumarine, dihydroquercetin, 3-O-a-L-rhamnopiranosyl-7-methoxy-5, 3’,4’-trihydroxyflavone, 3-O-a- L-rhamnopiranosyl- 5,7,3’,4’-tetrahydroxy flavone, quercetin, a flavonol and a gallic acid dimmers were identified using high resolution mass spectrometry by DART and ESI methods.

Os estudos químicos do extrato polar das folhas de Calliandra calothyrsus conduzem à identificação de dois flavonóides dos glicosilados: 3-O-a-L-ramnopiranosil- 7-metoxi-5,3’,4’-triidroxiflavona e 3-O-a-L-ramnopiranosil-5,7,3’,4’-tetraidroxiflavona; suas estruturas foram elucidadas pelos métodos de espectroscopia de absorção na região de infravermelho (IV) e espectroscopia de ressonância magnética nuclear RMN (1D e 2D). Também, por espectrometria de massas pela técnica DART e ESI identificaram- se derivados fenólicos tais como: ácido gálico, diidroxicumarina, triidroxicumarina, 3-O-a-L-ramnopiranosil-7- metoxi-5,3’,4’-triidroxiflavona, 3-O-a- L-ramnopiranosil-5,7,3’,4’-tetraidroxiflavona, quercetina, dihidroquercetina, um dímero do flavonóide e um dímero do ácido gálico como principais constituintes químicos.