A.K. Siddhanta

Detection and quantification of some plant growth regulators in a seaweed-based foliar spray employing a mass spectrometric technique sans chromatographic separation.

The sap expelled from the fresh harvest of Kappaphycus alvarezii , a red seaweed growing in tropical waters, has been reported to be a potent foliar spray. Tandem mass spectrometry of various organic extracts of the sap confirmed the presence of the plant growth regulators (PGRs) indole 3-acetic acid, gibberellin GA(3), kinetin, and zeatin. These PGRs were quantified in fresh state and after 1 year of storage by ESI-MS without recourse to chromatographic separation. Quantification was validated against HPLC data. The results may be useful in correlating with the efficacy of the sap. The methodology was extended to two other seaweeds. The method developed is convenient and precise and may find application in other agricultural formulations containing these growth hormones.

Sulphated polysaccharides of Codium dwarkense Boergs. from the west coast of India: chemical composition and blood anticoagulant activity.

Bioassay-guided purification of sulphated polysaccharides from a green marine alga, Codium dwarkense, yielded two products, which contained sulphated arabinan and sulphated arabinogalactan. The product containing arabinan sulphate exhibited stronger blood anticoagulant activity than the one containing sulphated arabinogalactan.

A new sulfated polysaccharide with potent blood anti-coagulant activity from the red seaweed Grateloupia indica

Abstract A sulfated galactan has been isolated from a red seaweed, Grateloupia indica (family: Grateloupiaceae), and has been found to possess a strong blood anti-coagulant activity.

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.

Microwave-induced facile synthesis of water-soluble fluorogenic alginic acid derivatives

A facile microwave-induced method was developed for synthesizing water-soluble fluorescent derivatives of alginic acid (ALG) with four different diamines, hydrazine (HY), ethylenediamine (EDA), 1,6-hexanediamine (HDA), and 1,4-cyclohexanediamine (CHDA), followed by a cross-linking reaction with a natural cross linker genipin. The ethylenediamine derivative of alginic acid (ALG-EDA) exhibited good fluorescent activity, which upon cross linking was enhanced threefold. The other amide derivatives, for example, ALG-HY, ALG-HDA, and ALG-CHDA, were not fluorescent, but their respective crosslinked products exhibited excellent fluorescent activity. The fluorescence intensity had an inverse correlation with the number of carbon atoms present in the amine, which in turn was a function of degree of substitution (DS). These fluorescent polysaccharide derivatives are of potential utility in the domain of sensor applications.

Fuel intermediates, agricultural nutrients and pure water from Kappaphycus alvarezii seaweed

The present work reports a standalone integrated scheme for the production of 5-hydroxymethyl furfural (HMF) and potassium sulphate (K2SO4) from granular biomass rich in the sulphated polysaccharide, κ-carrageenan. Fresh Kappaphycus alvarezii seaweed was crushed to expel the juice rich in KCl (0.7 m3 t−1 of fresh seaweed) and granular biomass (0.04 t dry weight per t of fresh seaweed). The latter yielded κ-carrageenan through seawater extraction. HMF was derived from this phycocolloid through reaction with Mg(HSO4)2 acid catalyst and isolated in pure form. Galactose was a co-product which remained in the aqueous phase. The aqueous phase was recycled up to 10 times by maintaining a constant acid strength, and utilized thereafter for the recovery of K2SO4. Selective crystallization of K2SO4 was guided by the phase diagram and use was made of a part of the seaweed juice in this process. The spent aqueous phase rich in galactose was subjected to further reaction with HCl obtainable through bipolar electro-dialysis (ED) of seaweed juice. The reaction yielded levulinic acid (LA) and formic acid (FA) in nearly equal proportions. The processing of 1 t of granular biomass was computed to require 30.15 GJ of energy and would yield 0.18 t HMF, 0.056 t LA, 0.020 t FA, 0.27 t K2SO4, and 5.77 m3 pure water. The process energy requirement for the scheme can be met from additional supplies of granule (3.35 t). Combustion/gasification of this biomass would yield additionally 0.74 t glaserite fertilizer and the required amount of H2SO4 for Mg(HSO4)2 preparation.

Synthesis of sodium alginate based sprayable new soft gel system

Chemical reaction of sodium alginate (Na-Alg) with o-aminobenzoic acid (OABA) and m-aminobenzoic acid (MABA) in the presence of 1-ethyl-3-[3-(dimethylamino)propyl]-carbodiimide hydrochloride (EDC) afforded amide derivatives capable of forming viscous hydrogel systems exhibiting thixotropic behaviour. Characterization of the amide materials was done by employing FT-IR and 13C NMR, wherein amide formation between Na-Alg and OABA or MABA was confirmed. The thixotropic behaviour was evaluated by rheology and viscometry showing superior thixotropicity of OABA based amide to its MABA counterpart. The characteristic of the soft gel turning into a flowing liquid on gentle stirring predisposes it for possible application as a delivery system or sprayable gel material for transporting small active molecules to the targeted locations in health and personal care formulations.

Chemical studies on the polysaccharides of Salicornia brachiata

A group of 12 polysaccharide extracts were prepared from the tips, stem and roots of an Indian halophyte Salicornia brachiata Roxb. obtained by sequential extractions with cold water (CW), hot water (HW), aqueous ammonium oxalate (OX) and aqueous sodium hydroxide (ALK) solutions. Monosaccharide composition analysis revealed that all the polysaccharide extract samples consisted primarily of rhamnose, arabinose, mannose, galactose, glucose, whereas ribose and xylose were present only in some of the extracts. All the extracts exhibited low apparent viscosity (1.47-2.02 cP) and sulphate and contained no prominent toxic metal ions. Fucose was detected only in OX extract of the roots. These polysaccharides were found to be heterogeneous and highly branched (glycoside linkage analysis, size-exclusion chromatography, (13)C-NMR, FT-IR, circular dichroism and optical rotation data). Physico-chemical analyses of these polysaccharides including uronic acid, sulphate and protein contents were also carried out. This constitutes the first report on the profiling of Salicornia polysaccharides.

Facile synthesis of agarose-L-phenylalanine ester hydrogels

Hydrogel forming agarose-L-phenylalanine ester (Ag-PAEst) was synthesized in a facile microwave mediated method involving the reaction of agarose with fluorenyl methyloxycarbonyl (Fmoc) protected amino acidL-phenylalanine (PA) in the presence of dicyclohexylcarbodiimide/4-dimethylaminopyridine (DCC/DMAP) followed by deprotection. Subsequently, the ester was cross-linked with the natural cross-linker genipin to yield a blue hydrogel (G-Ag-PAEst). Both the ester and cross-linked hydrogels had comparable gelling characteristics with agarose. These hydrogels were highly stable in all pH media (pH 1.2, 7.0 and 12.5) under ambient conditions. Physicochemical characterizations of the hydrogels were done by GPC, UV spectrophotometry, FT-IR, 1H- and 13C-NMR spectra. These hydrogels may have potential applications in microbiology, biomedical and pharmaceuticals fields.

Surfactant-induced coagulation of agarose from aqueous extract of Gracilaria dura seaweed as an energy-efficient alternative to the conventional freeze–thaw process

Surfactant-induced coagulation of agarose from alkali-treated Gracilaria dura seaweed extract (SE) is reported. The new approach, which was suitable for linear galactans with low sulphate content is an alternative to the traditional energy intensive process of “freeze–thaw” cycles employed for product isolation from the extract. Only nonionic surfactants were effective, and detailed studies were undertaken with octyl phenol ethoxylate (Triton X-100). The coagulated product was successively washed with water and water–isopropyl alcohol (IPA) to yield a fine powder of agarose in 13–15% yield (with respect to dry biomass). The product exhibited excellent properties [sulphate content: 0.2% w/w; degree of electro-endosmosis: 0.13; gel strength: 2200 g cm−2 (1% gel, w/v); and gelling temperature: 35 ± 1 °C] essential for demanding molecular biology applications, and the desired gel electrophoretic separation of DNA and RNA was demonstrated. It was further confirmed that there was no degradation of nucleic acids in the gel. The agarose-depleted extract, along with water used for washings, was subjected to reverse osmosis for recovering the surfactant in concentrated form for its subsequent reuse. Energy savings from the improved process were assessed.