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D-Glucans possess immunomodulatory activities and potential for the development of new therapeutic agents. Biological activities can be enhanced in these biopolymers through chemical derivatization, e.g., carboxymethylation. This work presents the carboxymethylation, characterization and the evaluation of antioxidant activities of the exocellular (1 → 6)-β-D-glucan produced by Lasiodiplodia theobromae MMPI. Thermal analysis indicated that the native and carboxymethylated polysaccharides presented four stages of mass-loss. The first stage occurred at 125°C (loss of water) with two consecutive events of mass loss (200-400°C) attributed to polymer degradation and the fourth stage between 425 and 620°C (final decomposition). Scanning electron microscopy analysis indicated that the gross morphological features of lasiodiplodan were ruptured following carboxymethylation. X-ray diffractometry analysis demonstrated that the native and carboxymethylated polysaccharides presented a non-crystalline structure. Carboxymethylation contributed to improving the polysaccharide's water solubility and antioxidant capacity.

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Summary:Purpose: Methylmalonic acid (MMA) inhibits succinate dehydrogenase (SDH) and β-hydroxybutyrate dehydrogenase activity in vitro. Acute intrastriatal administration of MMA induces convulsions through glutamatergic mechanisms probably involving primary adenosine triphosphate (ATP) depletion and free radical generation. In this study we investigated whether the intrastriatal administration of MMA causes lipoperoxidation and alteration in Na + , K + -ATPase activity ex vivo and characterized the electrographic changes elicited by the intrastriatal administration of this organic acid.Methods: MMA-induced lipoperoxidation, alterations in Na + , K + -ATPase activity and electrographic changes were measured by measuring total thiobarbituric acid-reacting substances and inorganic phosphate release by spectrophotometry, and by depth electrode recording, respectively.Results: We demonstrated that intrastriatal MMA (6 mmol) injection causes convulsive behavior and electrographically recorded convulsions that last ∼2 h. Concomitant with the increase of thiobarbituric acid-reacting substances (TBARS) content, we observed a significant inhibition of Na + ,K + -ATPase activity in the striatum, and activation of Na + ,K + -ATPase activity in the ipsilateral cerebral cortex. Intrastriatal MMA injection increased the content of TBARS in the striatum measured 30 min (32.4 ± 12.0%, compared with the noninjected contralateral striatum) and 3 h (39.7 ± 5.1%, compared with the noninjected contralateral striatum) after MMA injection. TBARS content of the ipsilateral cerebral cortex increased after MMA injection at 30 min (42.1 ± 6.0%) and 3 h (40.4 ± 20.2%), and Na + ,K + -ATPase activity in the ipsilateral cerebral cortex increased during ictal activity (113.8 ± 18%) and returned to basal levels as electrographic convulsions vanished in the cortex. Interestingly, intrastriatal MMA administration induced a persistent decrease in Na + ,K + -ATPase activity only in the injected striatum (44.9 ± 8.1% at 30 min and 68.7 ± 9.4 at 3 h).Conclusions: These data suggest that MMA induces lipoperoxidation associated with Na + ,K + -ATPase inhibition or activation, depending on the cerebral structure analyzed. It is suggested that Na + ,K + -ATPase inhibition may play a primary role in generating MMA-induced convulsions. Key Words: Na + ,K + -ATPase-TBARS-Methylmalonic academia-Methylmalonate-Convulsion-EEG-StriatumCortex-Rat.Methylmalonic acid (MMA) is the main metabolite that accumulates in the methylmalonic acidemias, which are inherited metabolic disorders caused by a severe deficiency of methylmalonyl-CoA mutase (EC 5.4.99.2) activity. These syndromes are clinically characterized by neurologic deficits, including delayed development, hypomyelination, convulsions, and hypotrophy of the basal ganglia. Other biochemical abnormalities occur as a result of the primary metabolic impairment, such as hyperammonemia, hypoglycemia, and metabolic acidosis (1). Accumulating evidence suggests that MMA may play a central role in the neurotoxicity cha...