NEUROPHARMACOLOGICAL EFFECTS OF THE BUFODIENOLIDES ISOLATED FROM Bufo paracnemis SKIN

CARVALHO, K.M.(1)

(1)Laboratório de Neurofarmacologia, Universidade Estadual do Ceará, Fortaleza, CE, Brazil.

Amphibians have undergone profound evolutionary changes to survive to predators and microorganisms, and their skin secretions containing toxins and several biological active substances seems to be a paramount importance. In this work, we shown new neuropharmacological effects of bufodienolides isolated from Bufo paracnemis parotoid secretion. After extraction, the secretion was dissolved in ethanol (1:4,w,v), centrifuged at 5000g/20min and submitted to HPLC chromatography using a C₁₈ column (25x250mm,5ml/min) eluted with acetonitrile (0-40%,30min). Fractions eluted with 38% and 40% of acetonitrile were pooled and lyophilized. High resolution NMR analysis by application of pulse sequences such as 1H, 1H-COSY and NOESY, carbon-detected and hydrogen-detected (inverse) hetero-nuclear correlation of directly attached carbon-hydrogen (HETCOR and HMQC, respectively), as well as the long-range equivalent sequences, COLOC and HMBC, allowed their identification as bufodienolides, known as marinobufagin and telecinobufagin. Telecinobufagin induced a strong local anesthetic activity assayed by: a) infiltration anesthesia: telecinobufagin(0.5%), 181±15min, bupivacaine(0.5%), 110±10min, and lidocaine(2%), 49±5min, b) mouse tail flick test: telecinobufagin(0.5%), 152±12min, bupivacaine(0.5%), 52±8min, and lidocaine(2%), 18.4±4min, c) cornea test: telecinobufagin(0.5%), 49.4±6min, bupivacaine(0.5%), 46.8±5min and lidocaine(2%), 11.5±3min, d) tooth pulp stimulation: telecinobufagin(0.5%), 160±12,5min, bupivacaine(0.5%), 150±11,9min and lidocaine(2%), 50±4,5min. These results suggest that telecinobufagin may be a prototype of a potent new class of local anesthetic. Marinobufagin induced a strong convulsant activity with seizures in the electrographic recordings in mice (5mg/kg,i.p.) and in rats (5mg/kg,i.p.), resulting in status epilepticus (>1h). Seizures decreased 100% in the animals pretreated with phenitoin (50mg/kg,i.p.) and 80% with diazepam (10mg/kg,i.p.), but they were not affected by phenobarbital(50mg/kg,i.p.). These results suggest that marinobufaginmay be used to develop an experimental status epilepticus model for the pharmacological evaluation of anticonvulsant drugs used in epilepsy treatment.

CORRESPONDENCE TO:

Krishnamurtide Morais Carvalho, Laboratório de Neurofarmacologia, Universidade Estadual do Ceará, Fortaleza, CE, Brazil, CEP: 60.000-000, Email: carvalhokris@hotmail.com