RESUMEN
Ursolic acid and uvaol are naturally occurring triterpenoids that exhibit a broad spectrum of pharmacological activities, including cytotoxicity. However, a primary challenge in the development of ursane-type pentacyclic triterpenoids for pharmacological use is their poor aqueous solubility, which can impede their effectiveness as therapeutics agents. In this study, we present the facile synthesis of ursolic acid monodesmosides and uvaol bidesmosides, incorporating naturally occurring and water-soluble pentoses and deoxyhexose sugar moieties of opposite d- and l-configurations at the C3 or C3/C28 positions of the ursane core. The twenty synthetic saponins were evaluated in vitro for their cytotoxicity against lung carcinoma (A549) and colorectal adenocarcinoma (DLD-1) cell lines. Notably, all the bidesmosidic uvaol saponins were shown to be cytotoxic as compared to their non-cytotoxic parent triterpenoid. For each series of ursane-type saponins, the most active compounds were 3-O-α-l-arabinopyranosyl ursolic acid (3h) and 3,28-di-O-α-l-rhamnopyranosyl uvaol (4f), showing IC50 values in the low micromolar range against A549 and DLD-1 cancer lines.
Asunto(s)
Ensayos de Selección de Medicamentos Antitumorales , Saponinas , Triterpenos , Humanos , Saponinas/farmacología , Saponinas/síntesis química , Saponinas/química , Triterpenos/química , Triterpenos/farmacología , Triterpenos/síntesis química , Línea Celular Tumoral , Relación Estructura-Actividad , Antineoplásicos/farmacología , Antineoplásicos/síntesis química , Antineoplásicos/química , Estructura Molecular , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Triterpenos PentacíclicosRESUMEN
Betulinic acid and ursolic acid are ubiquitous, naturally-occurring triterpenoids exhibiting various pharmacological activities including cytotoxic and anti-inflammatory activities. However, these triterpenoids display unfavorable pharmacokinetic properties as well as low aqueous solubility. It has been shown that the presence of α-l-rhamnose moieties positively modulates the anticancer activity of secondary metabolites. Herein we report the synthesis and in vitro evaluation of cytotoxic and anti-inflammatory activities of a series of rhamnose-containing ursolic and betulinic acid saponins. Relying on Schmidt's normal and inverse procedures, monorhamnosides, (1â4)-linked dirhamnosides as well as branched trirhamnosides and tetrarhamnosides were synthesized in high yields with full control of stereoselectivity. A betulinic acid saponin bearing a 3-O-α-l-rhamnopyranosyl-(1â4)-α-l-rhamnopyranosyl residue was found to be a potent cytotoxic agent against human colorectal adenocarcinoma cells without damaging the healthy cells (selectivity ratio > 20) whereas rhamnose-containing ursolic acid saponins potently inhibited NO overproduction induced by LPS-stimulated macrophages. Our results reveal that rhamnose-containing ursolic and betulinic acid saponins represent promising therapeutic agents.
RESUMEN
Betulin has a wide range of biological and pharmacological properties with its anticancer activity attracting most of the attention as it offers a possible alternative treatment to chemotherapy. However, betulin's in vivo biological effectiveness is limited by its poor solubility. As such, we synthesized polar glycosylated derivatives to increase its hydrosolubility and enhance its pharmacological properties. Among these synthesized compounds, 28-O-α-l-rhamnopyranosylbetulin 3ß-O-α-l-rhamnopyranoside (Bi-L-RhamBet) was assessed for its cytotoxic effects against a suite of lung cancer cell lines. We also investigated its mechanism of action using an A549 lung cancer cell line. Our results showed that Bi-L-RhamBet exhibited potent cytotoxic activity toward lung cancer cell lines including A549, NCI-H2087, NCI-H522, NCI-H1993 NCI-H1755, and LLC1 having IC50 values ranging from 2.9 to 5.9 µM. Moreover, Bi-L-RhamBet (50 mg/kg) significantly inhibited tumor growth with a treatment-to-control ratio (T/C) of 0.54 and a tumor growth inhibition rate of 46% at day 18 (p < 0.05). Microscopic observations of A549 cells, double stained with acridine orange and ethidium bromide, showed apoptotic features. Bi-L-RhamBet induced activation of pro-apoptotic caspases 8, 9, and 3/7 as well as causing DNA fragmentation. Moreover, a marked increase in mitochondrial ROS (mROS) was coupled with a reduction of mitochondrial potential. Interestingly, the presence of mitochondrial electron transport chain (ETC) inhibitors, including rotenone, malonate, and antimycin A, reduced mROS production, and the activation of caspases suggesting that Bi-L-RhamBet disturbs the ETC. Finally, dichloroacetate, a pyruvate dehydrogenase kinase inhibitor potentiated the cytotoxicity of Bi-L-RhamBet against A549 cells. Taken together, these data suggest that Bi-L-RhamBet can induce apoptotic cell death via disturbance of mitochondrial electron transfer chain, reduced ROS production, and decreased membrane potential.
Asunto(s)
Apoptosis/efectos de los fármacos , Ramnosa/química , Saponinas/toxicidad , Triterpenos/química , Triterpenos/toxicidad , Células A549 , Animales , Caspasas/metabolismo , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Fragmentación del ADN/efectos de los fármacos , Proteínas del Complejo de Cadena de Transporte de Electrón/antagonistas & inhibidores , Proteínas del Complejo de Cadena de Transporte de Electrón/metabolismo , Puntos de Control de la Fase G2 del Ciclo Celular/efectos de los fármacos , Humanos , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patología , Puntos de Control de la Fase M del Ciclo Celular/efectos de los fármacos , Masculino , Potencial de la Membrana Mitocondrial , Ratones , Ratones Endogámicos C57BL , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Rotenona/toxicidad , Saponinas/química , Saponinas/uso terapéutico , Trasplante Heterólogo , Triterpenos/uso terapéuticoRESUMEN
Laminarin is a ß-1,3-D-glucan displaying occasional ß-1,6 branches. This storage polysaccharide of brown algae constitutes an abundant source of carbon for marine bacteria such as Zobellia galactanivorans. This marine member of the Bacteroidetes possesses five putative ß-1,3-glucanases [four belonging to glycosyl hydrolase family 16 (GH16) and one to GH64] with various modular architectures. Here, the characterization of the ß-glucanase ZgLamC is reported. The catalytic GH16 module (ZgLamCGH16) was produced in Escherichia coli and purified. This recombinant enzyme has a preferential specificity for laminarin but also a significant activity on mixed-linked glucan (MLG). The structure of an inactive mutant of ZgLamCGH16 in complex with a thio-ß-1,3-hexaglucan substrate unravelled a straight active-site cleft with three additional pockets flanking subsites -1, -2 and -3. These lateral pockets are occupied by a glycerol, an acetate ion and a chloride ion, respectively. The presence of these molecules in the vicinity of the O6 hydroxyl group of each glucose moiety suggests that ZgLamCGH16 accommodates branched laminarins as substrates. Altogether, ZgLamC is a secreted laminarinase that is likely to be involved in the initial step of degradation of branched laminarin, while the previously characterized ZgLamA efficiently degrades unbranched laminarin and oligo-laminarins.
Asunto(s)
Celulasas/química , Celulasas/metabolismo , Flavobacteriaceae/enzimología , Glucanos/metabolismo , Secuencia de Aminoácidos , Dominio Catalítico , Cristalografía por Rayos X , Flavobacteriaceae/química , Flavobacteriaceae/metabolismo , Glucanos/química , Modelos Moleculares , Datos de Secuencia Molecular , Conformación Proteica , Proteoglicanos , Alineación de Secuencia , Especificidad por Sustrato , beta-Glucanos/química , beta-Glucanos/metabolismoRESUMEN
Recent developments of innovative anticancer therapies are based on compounds likely to stimulate the immune defense of the patients. ß-(1 â 3)-Glucans are natural polysaccharides well-known for their immunostimulating properties. We report here on the synthesis of small oligo-ß-(1 â 3)-glucans characterized by thioglycosidic linkages. The presence of sulfur atom(s) was not only crucial to prolong in vivo immunoactive activities in time, compared to native polysaccharides, but sulfur atoms also had a direct impact on the development of colorectal cancer stem cells. As a result, a short, pure, and structurally well-defined trisaccharidic thioglucan demonstrated similar activities compared to those of natural laminarin.
Asunto(s)
Adyuvantes Inmunológicos/química , Adyuvantes Inmunológicos/farmacología , Glucanos/química , Glucanos/farmacología , Adyuvantes Inmunológicos/síntesis química , Animales , Conformación de Carbohidratos , Secuencia de Carbohidratos , Línea Celular/efectos de los fármacos , Técnicas de Química Sintética , Citocinas/metabolismo , Evaluación Preclínica de Medicamentos , Femenino , Glucanos/síntesis química , Humanos , Ratones Endogámicos BALB C , Datos de Secuencia Molecular , Células Madre Neoplásicas/efectos de los fármacos , Fagocitosis/efectos de los fármacos , Relación Estructura-Actividad , Azufre/química , Trisacáridos/químicaRESUMEN
Hellecaucaside A, a new disaccharide nucleoside featuring a 2'-O-α-D-ribofuranosyluridine skeleton and a 4-hydroxybenzoyl group at the 5' position, was isolated from the underground part of Helleborus caucasicus. The structure of the compound was elucidated by means of chemical degradation and spectroscopic analyses, such as 1D/2D NMR, chiral-GC, and HRMS. The total synthesis of hellecaucaside A and its ß-anomer was accomplished, unequivocally confirming the structure of the natural product.
Asunto(s)
Disacáridos/química , Disacáridos/síntesis química , Helleborus/química , Nucleósidos/química , Uridina/análogos & derivados , Conformación de Carbohidratos , Técnicas de Química Sintética , Disacáridos/aislamiento & purificación , Estereoisomerismo , Uridina/síntesis química , Uridina/química , Uridina/aislamiento & purificaciónRESUMEN
A full characterization of the high-resolution NMR spectrum of the laminarihexaose is described and used for the determination of the binding epitope of the more complex but structurally related laminarin. These biophysical data extend the current knowledge of ß-glucans/Dectin-1 interactions and suggest different biological mechanisms in close relation with the size of the saccharidic chain.
Asunto(s)
Factores Inmunológicos/química , Antígeno de Macrófago-1/metabolismo , Espectroscopía de Resonancia Magnética/métodos , Proteínas de la Membrana/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Oligosacáridos/química , Polisacáridos/química , Proteínas Recombinantes/metabolismo , beta-Glucanos/química , Sitios de Unión , Secuencia de Carbohidratos , Mapeo Epitopo , Glucanos , Humanos , Factores Inmunológicos/metabolismo , Lectinas Tipo C , Antígeno de Macrófago-1/química , Antígeno de Macrófago-1/inmunología , Proteínas de la Membrana/química , Proteínas de la Membrana/inmunología , Modelos Moleculares , Datos de Secuencia Molecular , Proteínas del Tejido Nervioso/química , Proteínas del Tejido Nervioso/inmunología , Oligosacáridos/metabolismo , Polisacáridos/metabolismo , Unión Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/inmunología , Relación Estructura-Actividad , beta-Glucanos/metabolismoAsunto(s)
Productos Biológicos , Glicoconjugados , Factores Inmunológicos , Polisacáridos , Productos Biológicos/química , Productos Biológicos/farmacología , Glicoconjugados/química , Glicoconjugados/farmacología , Factores Inmunológicos/química , Factores Inmunológicos/farmacología , Polisacáridos/química , Polisacáridos/farmacologíaRESUMEN
It is known that 3-O-glycosylation of glucosidic acceptors bearing acyl groups in the 4 and 6 positions instead of a 4,6-O-benzylidene ring mainly affords alpha-glycosides. Described here is an unexpected stereochemical outcome for elongation at glucose O-3 of a beta-d-Glcp-(1-->3)-alpha-d-Manp disaccharide using peracetylated ethyl thioglucoside as a donor. This unexpected reaction was correlated with match-mismatch effects, as shown by efficient coupling of the same acceptor by a donor of l-configuration.
Asunto(s)
Glucanos/química , Glucanos/síntesis química , Manosa/química , Conformación de Carbohidratos , Glicosilación , Modelos Moleculares , Estereoisomerismo , Especificidad por SustratoRESUMEN
Cyclic thionocarbamates, namely chiral oxazolidinethiones (OZT) and aromatic oxazolinethiones (OXT), were involved, for the first time, in Sonogashira cross-coupling. A cooperative effect of two different copper (I) species-CuI and CuTC-accounts for this new copper-catalyzed desulfurative carbon-carbon cross-coupling reaction. This cooperative reactivity could also be extended to other copper (I) catalysts.
RESUMEN
A practical synthesis of acylated glycosyl isothiocyanates from sugar oxazolines, by reaction with thiophosgene, is reported. In the absence of any additive, the reaction is governed by the reverse anomeric effect, leading to the equatorially oriented isothiocyanate. However, in the presence of copper(II) chloride, the reaction proceeds preferentially with retention of the configuration at the anomeric center, providing the axial anomer as the major product. Noteworthy, this strategy allows accessing per-O-acetylated glycopyranosyl isothiocyanates with 1,2-cis relative configuration (e.g., the alpha-anomer in the D-gluco and D-galacto series), a problem that was outside the scope of previous methodologies.