Background: The snake venom group IIA secreted phospholipases A 2 (SVPLA 2 ), present in the Viperidae snake family exhibit a wide range of toxic and pharmacological effects. They exert their different functions by catalyzing the hydrolysis of phospholipids (PL) at the membrane/water interface and by highly specific direct binding to: (i) presynaptic membrane-bound or intracellular receptors; (ii) natural PLA 2 -inhibitors from snake serum; and (iii) coagulation factors present in human blood.

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Comprehensive knowledge of venom composition is very important for effective management of snake envenomation and antivenom preparation. Daboia russelii venom from the eastern region of India is the most neurotoxic among the four venom samples investigated. From the eastern D. russelii venom sample, neurotoxic peptide has been purified by combined method of ion exchange gel permeation chromatography and reversed phase high performance liquid chromatography. Molecular weight of Daboia neurotoxin III (DNTx-III) found to be 6,849 Da (as measured on matrix-assisted laser desorption/ionisation-time of flight mass spectrometer), and N-terminal amino acid sequences is I K C F I T P D U T S Q A. Approximate LD50 dosage was 0.24 mg/kg body weight. It produced concentration- and time-dependent inhibition of indirectly stimulated twitches of Rana hexadactyla sciatic nerve gastrocnemius muscle preparations. Chemical modification of DNTx-III tryptophan residue(s) reduced the twitch height inhibition property of toxin, signifying the importance of tryptophan residues for the neurotoxic function. This type of neurotoxic peptide is unique to east Indian regional D. russelii venom.