Ultrasound-assisted depolymerization of kappa-carrageenan and characterization of degradation product.

Degradation of polysaccharides to afford low-molecular-weight oligosaccharides have been shown to produce new bioactivities that are not present in the starting material. The simplicity of ultrasonic treatment in the degradation of a polysaccharide, such as κ-carrageenan, offers practical advantage in producing degraded products with lower molecular weight that may have new interesting potential activities. This study embarked on investigating the effects in molecular weights and structural changes of κ-carrageenan under varying ultrasonic conditions. Molecular weight (MW) monitoring of ultrasonically-treated κ-carrageenan at various conditions were done by gel permeation chromatography. The product formed using the optimized condition was characterized using FTIR and NMR. The decrease in MW has been shown to be dependent on low concentration (5.0 mg mL-1), high amplitude (85%), and long treatment time (180 mins) to afford a degraded κ-carrageenan with average molecular weight (AMW) of 41,864 Da, which is a 96.33% reduction from the raw sample with initial AMW of 1,139,927 Da. Structural analysis reveals that most of the peaks of the raw κ-carrageenan was retained with minor change. 1D and 2D NMR analyses showed that the sonic process afforded a product where the sulfate group at the G4S-4 position was cleaved forming a methylene in the G4S ring. The results would be useful in the structure-activity relationship of κ-carrageenan oligosaccharides and in understanding the effect in the various potential applications of degraded κ-carrageenan.

Hemostatic efficacy evaluation of radiation-crosslinked carboxymethyl cellulose granules and kappa-carrageenan/polyethylene oxide/polyethylene glycol dressing in rat bleeding models.

Carboxymethyl cellulose granules (CMC-G) and kappa-carrageenan/polyethylene oxide/polyethylene glycol dressing (KPP-D) hemostatic agents, developed through radiation-induced crosslinking and sterilization, were tested in Sprague-Dawley rats using three bleeding models: (a) deep wound with the puncture of femoral artery; (b) aortic puncture; and (c) partial nephrectomy. Dressing and granules were applied in the animals without sustained compression and monitored for a period of 7 or 14 days. Comparisons were made against the commercial chitosan-based agent, Celox (CLX). Primary outcomes observed were bleeding time, the incidence of re-bleeding, animal survival, as well as gross and microscopic changes. The KPP-D group showed the shortest bleeding time for all bleeding models (a. 2.75 ± 0.64, b. 1.63 ± 0.54, c. 2.05 ± 0.62), significantly faster than all the other treatment groups. KPP-D also registered the highest survival rate of 100% with no display of gross abnormalities. CMC-G showed comparable bleeding time with CLX products but had a better survival rate at 98% compared to 96%. The incidence of re-bleeding was greater in CLX treated groups as well as more occurrence of granular adhesions that impacted mortality outcomes. Findings indicate the efficacy of KPP-D in the treatment of severe hemorrhage due to traumatic injury and intraoperative cases, while CMC-G was more suited for external trauma. Complications arising from inflammation, granules deposition, and adhesions emphasize stringent handling and removal of granular hemostat as a critical consideration in hemostat development and testing.

Antioxidant activity potential of gamma irradiated carrageenan.

The antioxidant capacity of irradiated κ-, ι-, λ-carrageenans were investigated using the hydroxyl radical scavenging assay, reducing power assay and DPPH radical scavenging capacity assay. The degree of oxidative inhibition increased with increasing concentration and dose. The type of carrageenan had also an influence on its antioxidant activity which followed the order of lambda

Comparative studies on the conformational change and aggregation behavior of irradiated carrageenans and agar by dynamic light scattering.

The conformational associative properties of kappa-, iota-, and lambda-carrageenan and agar with irradiation dose were studied by dynamic light scattering. The random scission of the carrageenans and agar by gamma irradiation resulted in the formation of polydispersed lower molecular weight fragments. At high doses, the system moves towards uniformity. Conformational change from coil to helix was observed in all carrageenans and agar at doses up to 100 kGy. The conformational change in lambda-carrageenan may be due to the irregular and hybrid structure of this polysaccharide. Only agar and lambda-carrageenan still undergo conformational transition at a high dose of 200 kGy. Gelation is observed for kappa-, iota-carrageenan up to a dose of 50 kGy while gelation is still observed at 100 kGy for agar. Increase in the hydrodynamic radius with decreasing temperatures for the non-irradiated carrageenans follows this order: lambda-carrageenan>kappa-carrageenan>iota-carrageenan. Slight increases in hydrodynamic radius were observed with irradiation.