Banca de DEFESA: LUCAS ALIGHIERI NEVES COSTA BATISTA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : LUCAS ALIGHIERI NEVES COSTA BATISTA
DATE: 27/03/2020
TIME: 14:00
LOCAL: Sala Carl Peter von Dietrich
TITLE:

Characterization of Sulfated Polysaccharides Rich Fractions from Brown Seaweed Dictyopteris delicatula and its Antiurolytic Potential Evaluation, from Determination of its Antioxidant Activity and Calcium Oxalate Crystallization Modulation

KEY WORDS:

heterofucans, brown algae, antioxidant, kidney stones and sulfated polysaccharides

PAGES: 123
BIG AREA: Ciências Biológicas
AREA: Bioquímica
SUMMARY:

Fucans and fucoidans are polysaccharides that contain sulfated L-fucose in their constitution and are found in brown algae, several pharmacological activities are attributed to these molecules such as: anticoagulant, antithrombotic, antiproliferative, anti-nociceptive, osteogenic and others. Wide presence of carboxyl and sulfate groups in fucans and fucoidans gives these molecules a high negative charge, which is a common characteristic of inhibitors of calcium oxalate (CaOx) kidney stones formation, so fucans and fucoidans are probably antiurolithic agents, which has already been demonstrated in some studies. Antiurolithic activity is also related to reduction of oxidative stress in renal tubules therefore fucans and fucoidans are also considered antiurolytic due to their antioxidant action. Considering the negative charge and antioxidant activity as a key factor for antiurolithic activity, the present study aims to evaluate the antiurolithic potential of polysaccharides extracted from the macroalgae Dictyopteris delicatula - a macroalgae widely found throughout the northeastern coast - through analysis of these polysaccharides effect in CaOx crystallization and their potential to prevent oxidative stress in MDCK cells. D. delicatula total polysaccharides were extracted by proteolysis and fractionated by precipitation with increasing volumes of acetone in five different fractions: F0.5v, F0.7v, F1.0v, F1.5v and F2.0v. Fractions compositions was determined by physical-chemical analysis, which proved they were sulfated polysaccharides rich fractions (SPRF). CaOx crystallization was induced in vitro by adding sodium oxalate to a solution of calcium chloride, which contained or not one of the FRPS solution. When formed in the presence of FRPS, CaOx crystals are smaller, more numerous and with a highly negative surface charge, with emphasis on the F0.5v modulatory activity, whose presence in crystallization increased 1721 times the number of crystals formed, reduced by more than 90 % crystals size, increased the negative charge on the surface from -7 mV to -35 mV and completely prevented the formation of monohydrated CaOx crystals, based on these results the F0.5v was chosen to be better evaluated. F0.5v was fractionated by ion exchange chromatography and five subfractions were obtained: 0.2 M, 0.4 M, 0.5 M, 0.6 M and 1.0 M. The chemical characterization of F0.5v and its subfractions revealed that F0.5v is consisting of alginate, heterofucans and laminarin. The antioxidant and CaOx crystallization modulating activities of none of the subfractions were superior to the activities of unfractionated F0.5v, indicating that F0.5v is more efficient when in the native form. Regarding the antioxidant activity, F0.5v was able to scavenge 79% of hydroxyl radicals, 10% of superoxide radicals, 22% of nitric oxide and have antioxidant capacity equivalent to 31 mg of ascorbic acid, in addition it has antioxidant activity ex vivo and increased up from 55% to 100% the viability of renal cells exposed to hydrogen peroxide, as for the modulation in crystallization, F0.5v, even in small concentrations like 0.01 mg / mL, promotes heterogeneous nucleation and the formation of small, dihydrated and unaggregable crystals. Considering the antioxidant and modulatory activity of CaOx crystallization of F0.5v we conclude this compound has the potential to prevent the formation of renal CaOx stones.

BANKING MEMBERS:
Presidente - 2195251 - HUGO ALEXANDRE DE OLIVEIRA ROCHA
Interna - 1453487 - KATIA CASTANHO SCORTECCI
Externo à Instituição - RANIERE FAGUNDES DE MELO SILVEIRA