Pablyana L.R. Cunha

Oxidation of cashew tree gum exudate polysaccharide with TEMPO reagent

Cashew gum (CG), an exudate polysaccharide from Anacardium ocidentale trees, was oxidized with TEMPO reagent and the 7product (CGOX) characterized by spectroscopic techniques (FT-IR and NMR), chromatographic analyses (HPLC and GPC), viscosity measurements and thermal analysis (TGA). The yield of the reaction product was 96%. The uronic acid content in starting gum (7.2 m%) was increased to 36 m%. The degree of oxidation based on free galactose and glucose units was 68%. NMR data show that oxidation occurred preferentially at primary carbons of galactose units. High degradation degree after oxidation was estimated by the difference on the expected and observed hCGOX/hCG ratio. The presence of organic and inorganic impurities in the new polyelectrolyte was detected by TGA. A less thermally stable cashew gum is formed after the oxidation with TEMPO based on initial decomposition temperature and IPDT.

Sulfated chitosan as tear substitute with no antimicrobial activity.

Chitosan of high molar mass and with 82% deacetylation was sulfated using two procedures and characterized. In the first method sample chitosan-S1 was produced using chlorosulfonic acid as the sulfating agent and N,N-dimethylformamide as the medium, and in the second method (chitosan-S2) formic acid was also used. The degrees of sulfation were 0.87 (chitosan-S1) and 0.67 (chitosan-S2). FTIR spectra showed bands at 1230, 800 and 580 cm(-1), attributed to sulfation. Moisture content followed the order: chitosan-S-0.87>chitosan-S-0.67>chitosan. Chain depolymerization was verified by GPC. Aqueous solutions showed pseudoplastic behavior and the viscosity at a concentration of 0.3% (w/v) was higher than that of healthy human tears (close to 3 mPas at shear rate 130 s(-1)). Substitutions in the C2NH and in C6OH groups were verified by NMR. Antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa was not observed. Considering that chitosan-S-0.67 had a higher solubility, less chain depolymerization, higher yield and better thermal stability in comparison with chitosan-S-0.87, the derivative with DS 0.67 offered the greatest potential for use in formulations of tear substitutes.

Novel and Fast Microwave-Assisted Synthesis of Carbon Quantum Dots from Raw Cashew Gum

Carbon quantum dots (C-dots) with average size of 9 nm were synthesized from an aqueous solution of raw cashew gum (RCG) using a novel and fast microwave-assisted technique which involves two steps. In the first step (partial depolymerization in solution) some monomer units are formed through the autohydrolysis of CG and a small amount of 5-hydroxymethyl furfural can be obtained. The second step involves polycondensation/polymerization to give rise to a polyfuranic structure followed by aromatization/carbonization and nuclear burst. At the end of the process a composite of partially depolymerized CG and C-dot was formed. A mechanism involved in microwave-assisted two-steps synthesis was suggested. Although no passivation reagent was used, an intensely blue photoluminescent material in UV light was obtained. C-dot was characterized by spectroscopy in the medium infrared, thermal analysis, gel permeation chromatography, transmission electron microscopy, zeta potential, and photoluminescence.

Viscoelásticos oftálmicos: comparação entre os comerciais e formulações de galactomanana de Dimorphandra gardneriana

Ophthalmic viscosurgical devices (OVD) are materials injected in intraocular space during cataract removal to reduce trauma in the patients eye. Three Brazilian commercially available OVDs (Medilon®, Metilcelulose® and Ofthyal®) were evaluated as well as formulations based on Dimorphandra gardneriana galactomannan. Viscosity and viscoelastic parameters, such as viscosity at zero shear, pseudoplasticity index, elastic and viscous moduli, relaxation time, were determined and compared. Characteristics of an effective OVD were proposed. None of the Brazilian devices studied fulfill the rheological requirements. Only the galactomannan at 3% concentration showed potential to be used as effective OVD.

AB0068 Structural Characteristics of Polysaccharides Influence Viscosupplementation Efficacy in Osteoarthritis

Background Intra-articular (i.a) injection of a purified Guar gum (GG) solution or hydrogel provided analgesia similar to that of Hylan G-F20 in experimental osteoarthritis (eOA) suggesting that rheology is not crucial to viscosupplements. Objectives Evaluate the effect of purified GG (DGG), sulfated (DGGSU) of oxidized (DGGOX) GG on pain and cartilage damage in eOA Methods GG was oxidated with a n-oxil-2, 2, 6, 6-tetra metilpiperidina (TEMPO) reagent or subjected to sulfation to produce carboxylated and sulphate groups. Rats subjected to anterior cruciate ligament transection (ACLT) of the knee received 100 μg GG, sulfated or oxidized GG or vehicle (NT) i.a. at day 4 to 7 after ACLT. Joint pain was recorded using the articular incapacitation test. A group received GG weekly or vehicle from day 7 to 70 and joint damage assessed by histology and biochemically, measuring hondroitin-sulfate (CS) cartilage content (μg/mg) and Mw of CS through PAGE. Results FT-InfraRed spectra of DDGSU and DDGOX were different from protein free DGG. DGGSU has a new intense band at 1262 cm–1, due to S=O. Spectral difference occurs in DGGOX but not DGG and a C=O stretching is present in DGGOX spectrum (COOH group). 13C NMR spectrum of DGGOX and DGG revealed absence of the signal at 63.7 ppm present in DGG and two new signals at 177.5 and 177.8 ppm. Absence of the signal from C-6 of free mannose indicates it was substituted in the oxidation. The new signals are from C=O group from COOH. 1H-13C HSQC spectra exhibited a shift to a lower d value of the proton H-1 from mannose residue in DGGOX, indicating substitution at C-6 from mannose. New signals at 70.3, 75.6, and 100.5 ppm were observed in 13C NMR spectrum of sulfated gum due to the insertion of sulfate group in the primary carbon (C-6). All derivatives show lower molar mass than the original guar gum. DGG Mw =3.9 x 106 g/mol, DGGOX and DGGSU, 2.6 x 106 and 2.8 x 106 g/mol, respectively. DGGOX has the lowest intrinsic (2.2 dL/g) and apparent viscosity (9.0 mPa s).DGG exhibits the highest values ([h] =6.2 dL/g and happ =58 mPa s). Intermediate values are obtained for DGGSU ([h] =4.9 dL/g and happ =39 mPa s). GG significantly reduced joint pain, as compared to vehicle whereas oxidat ion or sulfation of GG abrogated GG analgesia. GG also prevented the increase in both CS content (43.8±4.7 μg/mg) and Mw (mobility: 1.18 ±0.03), as compared to NT (p<0.001). GG also significantly prevented joint damage at histopathology (median =7; range 2.5 - 18), as compared to NT (p<0.05). Conclusions The structural integrity of GG is crucial to its analgesia. Intra-articular polysaccharides can be analgesic and chondroprotective regardless of being water-soluble. Acknowledgement Supported by grants 302218/2014–9 and 459334/2014–0 from CNPq-Brasil). Disclosure of Interest None declared