Modification of agarose: 6-aminoagarose mediated syntheses of fluorogenic pyridine carboxylic acid amides.

A facile 6-aminoagarose (AA) mediated synthesis of new fluorogenic amides of agarose with nicotinic (AA-NA) and picolinic acids (AA-PA) employing carbodiimide chemistry have been described. 6-Amino agarose (AA) was synthesized in a facile Mitsunobu-inspired microwave mediated method involving the reaction of agarose with phthalimide in presence of diisopropyl azodicarboxylate and triphenylphosphene (DIAD/TPP) followed by hydrazinolysis. All compounds were characterized by GPC, UV spectrophotometry, fluorescence spectroscopy, FT-IR, (1)H and (13)C NMR spectra. The fluorescence emissions (λmax 430 and 412 nm) of 1 × 10(-3)M solutions of AA-NA and AA-PA in water were significantly higher (ca. 82% and ca. 90%) than those of the molar equivalents (0.2mg) of NA and PA present in the 1 × 10(-3)M solutions of the amides, respectively. These fluorogenic pyridine carboxylic acid amides of agarose may find applications as sensors in biomedical and pharmaceutical industries.

Cellulose contents of some abundant Indian seaweed species.

Crude cellulose as well as alpha- and beta-celluloses were estimated in thirty-four seaweed species of fifteen orders of Chlorophyta, Phaeophyta and Rhodophyta of Indian waters. The greatest yields of crude cellulose and a-cellulose were obtained from Chaetomorpha aerea (approx. 20.0% and 18.5%, respectively), and of beta-cellulose (approx. 3.1%) from Caulerpa imbricata. The lowest crude cellulose, and alpha-and beta-contents were recorded for the calcareous red alga Liagora indica (approx. 0.90%, 0.70% and 0.10%, respectively). There was little variation in cellulose content among the brown algae, while wide variations in the yields were found in the green and red algae. The present work contributes to the repertoire of 67 Indian seaweed species studied to now for their cellulose contents in our laboratory. The combined studies highlight that Chaetomorpha aerea, Acrosiphonia orientalis, Caulerpa taxifolia, Sargassum tenerrimum, Hydroclathrus clathratus and Gelidiella acerosa possess relatively high (> 10%) cellulose contents, which could be of potential utility.

Chemical investigation of carrageenan from the red alga Sarconema filiforme (Gigartinales, Rhodophyta) of Indian waters.

Sulphated galactan (SF(A)) containing alpha (alpha), iota (i) and pyruvated alpha-carrageenans (17.6:18.8:25.3 mol %) was extracted and characterized from Sarconema filiforme of Indian waters. The SF(A) and its alkali modified derivative (SF(AM)) were composed of D-galactose, 3, 6-anhydro-D-galactose, 6-O-methylated-D-galactose (64.5:23.0:9.8 and 59.6:29.8:7.6 mol %) respectively. The linkage analysis, physicochemical analysis, infra red and 13C nuclear magnetic resonance spectra of SFA along with linkage analysis of the desulphated derivative (SF(D)) of SFA, reveals that it was a hybrid/combination of alpha/iota carrageenan as well as 3-linked 4',6'-O-(1-carboxyethylidene)-galactose (pyruvated alpha carrageenan) and 6-O-methylated alpha-carrageenan. The flow behavior of SF(A) obtained from rheological measurements suggested strong network formation in presence of 1% aqueous KCl and CaCl2 solutions.

Profiling of cellulose content in Indian seaweed species.

Cellulose contents were estimated in 12 seaweed samples belonging to different families e.g. red, brown and green, growing in Indian waters. Each cellulose sample was fractionated to yield alpha (alpha) and beta (beta) celluloses. Characterization was done using various analytical tools and results were validated by comparison with those of the cellulose obtained from Whatman filter paper No. 4. The greatest yields of cellulose (crude), alpha- and beta-cellulose were obtained from Gelidiella acerosa (13.65%), Chamaedoris auriculata (9.0%) and G. acerosa (3.10%). G. acerosa was also found to contain relatively high amount of alpha-cellulose (8.19%). The lowest cellulose contents were recorded from Kappaphycus alvarezii (2.00%) and Sarconema scinaioides (2.1%), while the latter contained the lowest alpha-, and beta-celluloses (1.0% and 0.30%, respectively). It appears that agarophytic and alginophytic algae contain high cellulose and alpha-cellulose contents, while the carrageenophyte contains low cellulose. The brown algae, in general contain high cellulose as well as alpha- and beta-celluloses.