The anticonvulsant effect of a polysaccharide-rich extract from Genipa americana leaves is mediated by GABA receptor

Background: This study aimed to chemically characterize a polysaccharide-rich extract (PRE) obtained from Genipa americana leaves and evaluate its neuroprotective effect in the brain morphology and oxidative markers using mice behavioral models. Methods: Dry powder (5 g) of G. americana leaves were submitted to depigmentation in methanol. PRE was obtained by extraction in NaOH and precipitation with absolute ethanol and characterized by infrared spectroscopy (FTIR) and nuclear magnetic resonance (H-1 and C-13 NMR). Swiss mice (25-35 g) received saline (0.9% NaCl) or PRE (1-27 mg/kg) by intraperitoneal (i.p.) route, 30 min before evaluation in behavioral models (open field, elevated plus maze, sleeping time, tail suspension, forced swimming, seizures induced by pentylenetetrazole-PTZ). Animal's brain were dissected and analyzed for histological alterations and oxidative stress. Results: FTIR spectrum showed bands around 3417 cm(-1) and 2928 cm(-1), relative to the vibrational stretching of O-H and C-H, respectively. H-1 NMR spectrum revealed signals at delta 3.85 (methoxyl groups) and delta 2.4 (acetyl) ppm. C-13 NMR spectrum revealed signals at delta 108.0 and delta 61.5 ppm, corresponding to C1 and C5 of alpha-L-arabinofuranosyl residues. PRE presented central inhibitory effect, increasing the latency for PTZ-induced seizures by 63% (9 mg/kg) and 55% (27 mg/kg), and the latency to death by 73% (9 mg/kg) and 72% (27 mg/kg). Both effects were reversed by the association with flumazenil. Conclusions: PRE, containing a heteropolysaccharide, presents antioxidant and anticonvulsant effect in the model of PTZ-induced seizures via gamma-aminobutyric acid (GABA), decreasing the number of hippocampal black neurons.