BIOLOGICAL ACTIVITY AND PURIFICATION OF A NEUROTOXIN FROM Averrhoa carambola STAR FRUIT (OXALIDACEAE)

CAROLINO, R.O.G.(1), BELEBONI, R. O.(1), MOYSES-NETO, M.(3), CAIRASCO, N. G.(2), COUTINHO-NETTO, J.(1)

(1)Biochemistry and Immunology, (2)Physiology Departments and (3)Nephrology Divisions (HCRP), FMRP, USP, SP, Brazil

Objectives: The consumption of star fruit (A. carambola) is very widespread in Brazil. However, the consumption of star fruit can be hazardous to patients suffering of renal failure. The symptoms vary from nausea, vomiting, intractable hiccups, insomnia, psychomotor agitation and several degrees of conscious alterations, persistent convulsions and death. The aim of this work was to isolate the active fraction, responsible for convulsions from star fruit, as well to study its action on GABAergic and glutamatergic systems.

Methods and results: Fruits were collected from trees non treated with pesticides, homogenized in distilled water 1:1 (w/v) and sequentially treated with lead acetate and ammonium sulfate. This extract was submitted to DEAE, CM-cellulose and reverse phase HPLC chromatography. The active fraction (referred as to AcTx) was able to induce convulsion and death after intracisternal administration in mice. L-glutamate and GABA uptake as well as glutamate release in synaptosomes from rat cerebral cortex were not altered in presence of AcTx. On the other hand, AcTx displaced ³H-GABA binding from its receptors in synaptic membranes, but did not alter glutamate binding. Acid hydrolysis and amino acids analysis revealed no amino acids in its structure.

Conclusions: The star fruit has a neurotoxic compound, not a peptide, acting through GABA receptors. Further studies are on its way to better explain the intoxication symptoms and the complete chemical structure.

Financial support: CAPES e FAPESP.

CORRESPONDENCE TO:

Joaquim Coutinho Netto, Avenida Bandeirante, 3900, Monte Alegre, Ribeirão Preto, SP,  CEP: 14049-900, Brasil, Email: jcnetto@fmrp.usp.br