I isolated polysaccharide from a plant and its giving strong fluorescence in UV light, but not giving any quenching with AlCl3 in UV absorption spectrum, I hope it contains a aromatic ring. Apart from GC-MS , how can I determine the presence of aromatic rings?
Of course first rule out that you are seeing an impurity by attempting further separation. Since your compound must be very polar and with a large molecular weight, I suppose you would use an HP-SEC column or HPLC-C18 with a very low % organic to see if any chromophoric impurities separate out.
When your sure you have a pure polysaccharide, NMR would provide possibly the strongest evidence for an aromatic ring (if you have enough material) because you will have proton signals in the 6 to 8 ppm aromatic region which would be a clean with a normal polysaccharide. But signals in this region could also be from double bonds, so you will probably need both NMR and MS/MS fragmentation data to determine what the chromophore is. What plant did you isolate it from? I am curious since I am working on a paper involving oligosaccharides containing aromatic rings attached.
look If it's aromatic ring is present in your molecule u can simply check ur sample under water bath heating then adding equivalent mole or excess conc.HNO3 with heating then neutralized with 6M NaOH untill the pH approximately =9-10 if u observed a yellow color , that mean ur molecule have an aromatic ring ( nitration occurred ). then u can move forward to analyze the sample by spectroscopic tools.
@ Andrew Newsome @ i isolated the compound further by DEAE cellulose column and purified by the sephadex column.
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