Studies on the cobra neurotoxin inhibiting activity in an extract of Curcuma sp. (Zingiberaceae) rhizome.

A study was carried on the mode of action and some properties of a cobra neurotoxin inhibitor found in the extract of Curcuma sp. (Zingiberaceae). When the principal postsynaptic neurotoxin (STX) of the Thai cobra (Naja naja siamensis) was mixed with an aqueous extract of Curcuma sp. rhizome, the STX was inactivated as tested in mice or in vitro using a rat hemidiaphragm preparation. The 'neurotoxin inhibitor' ('NTxI') was found only in the water insoluble fraction of the rhizome extract. Using radioactively labeled neurotoxins, 125I-STX and 3H-STX, it was demonstrated that the neurotoxin did not form a stable complex with the 'NTxI'; the inactivated neurotoxin remained in the supernatant of the reaction mixture. After inactivation by 'NTxI', the STX exhibited an unchanged molecular weight as judged by SDS-polyacrylamide gel electrophoresis and an unchanged isoelectric point in isoelectric focusing. Extraction of the Curcuma sp. rhizome with at least 0.2% Triton X-100 resulted in solubilization of a component capable of forming a soluble and stable complex with 3H-STX. By column chromatography on Sephadex G-200 in the presence of 0.1% Triton X-100, the toxin-binding compound was shown to have a molecular weight of about 150 kDa. This 150 kDa component was obtained by Triton extraction of the water-insoluble fraction, and much less from the water soluble fraction, of Curcuma sp. rhizome. It did not possess any carbohydrate side-chain capable of binding the lectin Concanavalin A. The time course of the 150 kDa-3H-STX complex formation was extremely slow (approx 22 hours).(ABSTRACT TRUNCATED AT 250 WORDS)

Proteolytic-independent cobra neurotoxin inhibiting activity of Curcuma sp. (Zingiberaceae).

The 1: 1 (w/v) aqueous extract of Curcuma sp. (Zingiberaceae) was shown to antagonize the toxic action of Naja naja siamensis neurotoxin possibly via direct inactivation of the toxin. The plant extract possessed proteolytic activity which could be separated from the neurotoxin inhibiting activity. The mechanism of antagonism between the plant extract and the neurotoxin was shown not to be involved with the existence of proteolytic activity in the plant extract.

The absence of antagonism between extracts of Clinacanthus nutans Burm. and Naja naja siamensis venom.

Clinacanthus nutans Burm, a herb reputed in Thailand and Malaysia to be "snakebite antidote" has been tested in vitro and in vivo for antivenin activity. The aqueous extract of C. nutans leaves has been found to have no effect on the inhibition of neuromuscular transmission produced by purified Naja naja siamensis neurotoxin in isolated rat phrenic-nerve diaphragm preparations. The extract of C. nutans, when given orally or intraperitoneally, are ineffective in prolonging the survival time of experimental mice receiving lethal doses of N.n. siamensis crude venom. Oral administrations of the herb extracts pretreated with alpha-amylase or beta-amylase also fail to protect the animal. It is concluded that the extract of C. nutans can not antagonize the action of cobra venom.