CHARACTERISATION OF LIGNIN EXTRACTED FROM SIX MANGROVE SPECIES GROWN IN BANGLADESH

Lignin from six mangrove species [namely, keora (Sonneratia apetala), gewa (Excoecaria agallocha), bine (Avicennia alba), sundri (Heritiera fomes), pashur (Xyloccarpous mekongests) and kakra (Bruguiera gymnorhiza)] was extracted by acidic dioxane. The isolated lignin was submitted to structural characterization employing spectroscopic techniques (FTIR, H-1-NMR), as well as elemental analysis, molecular weight and methoxyl content determination. Results showed that the lignin of these mangrove species was mainly of the syringyl type (S), followed by the guaiacyl type (G). The polydispersity of the mangrove species lignin was very high. NMR spectra showed that the erythro protons (H alpha) give a stronger peak at 6.01 ppm than the corresponding peak for the threo form at 6.09 ppm in bine, gewa, kakra and sundari lignins, while keora lignin showed almost equal intensity.