RESUMEN
Zosterin, an apiose-rich pectic polysaccharide, was extracted and purified from the sea grass Zostera marina. Structural studies conducted by gas chromatography and NMR spectroscopy on a purified zosterin fraction (AGU) revealed a typical apiogalacturonan structure comprising an alpha-1,4-d-galactopyranosyluronan backbone substituted by 1,2-linked apiofuranose oligosaccharides and single apiose residues. The average molecular mass of AGU was estimated to be about 4100 Da with a low polydispersity. AGU inhibited proliferation of A431 human epidermoid carcinoma cells with an approximate IC(50) value of 3 microg/mL (0.7 microM). In addition, AGU inhibited A431 cell migration and invasion. Preliminary experiments showed that inhibition of metalloproteases expression could play a role in these antimigration and anti-invasive properties. Autohydrolysis of AGU, which eliminated apiose and oligo-apiose substituents, led to a virtual disappearance of cytotoxic properties, thus suggesting a direct structure-function relationship with the apiose-rich hairy region of AGU.
Asunto(s)
Antineoplásicos Fitogénicos/aislamiento & purificación , Antineoplásicos Fitogénicos/farmacología , Pectinas/aislamiento & purificación , Pectinas/farmacología , Polisacáridos/química , Zosteraceae/química , Antineoplásicos Fitogénicos/química , Pared Celular/química , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Concentración 50 Inhibidora , Biología Marina , Estructura Molecular , Monosacáridos/análisis , Resonancia Magnética Nuclear Biomolecular , Pectinas/química , Pentosas/análisis , Relación Estructura-ActividadRESUMEN
Hardwood 4-O-methylglucuronoxylans (MGX) are classically isolated by a delignification step, using a sodium chlorite solution, followed by alkaline extraction, an efficient, although potentially polluting process. In this work, we propose a chlorine-free environmentally-friendly process for MGX extraction from Castanea sativa Mill. Chestnut sawdust was first delignified using metalled phthalocyanine or porphyrin in presence of hydrogen peroxide. Then, MGX were easily extracted by hot water. This protocol, repeated with different incubation times and temperatures, led to the selective extraction of acetylated MGX with decent yields reaching 12%. The best results were obtained after delignification using iron tetrapyrrole macrocycles. However, lower degrees of polymerization of MGX were observed in comparison to the classical method, suggesting that this new process affects the structures of xylans.
Asunto(s)
Fagaceae/química , Peróxido de Hidrógeno/química , Indoles/química , Lignina/química , Porfirinas/química , Madera/química , Xilanos/aislamiento & purificación , Isoindoles , Oxidación-Reducción , Espectrofotometría Ultravioleta , Agua/químicaRESUMEN
Xylans were purified from delignified holocellulose alkaline extracts of Castanea sativa (Spanish chestnut) and Argania spinosa (Argan tree) and their structures analyzed by means of GC of their per-trimethylsilylated methylglycoside derivatives and (1)H NMR spectroscopy. The structures deduced were characteristic of a 4-O-methylglucuronoxylan (MGX) and a homoxylan (HX), respectively, with degrees of polymerization ranging from 182 to 360. In the case of MGX, the regular or random distribution of 4-O-methylglucuronic acid along the xylosyl backbone--determined by MALDI mass spectrometry after autohydrolysis of the polysaccharide--varied and depended both on the botanical source from which they were extracted and on the xylan extraction procedure. The MGX also inhibited in different ways the proliferation as well as the migration and invasion capability of A431 human epidermoid carcinoma cells. These biological properties could be correlated with structural features including values of the degree of polymerization, 4-O-MeGlcA to xylose ratios, and distribution of 4-O-MeGlcA along the xylosyl backbone, giving evidence of a defined structure-activity relationship.