Toxicity, teratogenicity and antibacterial activity of posterior salivary gland (PSG) toxin from the cuttlefish Sepia pharaonis (Ehrenberg, 1831)

- Ionic peptide rich PSG toxin from S. pharaonis was isolated using IEC and RP-HPLC.
- Corrosive effect of PSG toxin was determined by SEM and EDX of amberlite IRA 900 Cl− resin.
- PSG toxin exhibited pronounced developmental malformations against Zebrafish embryo.
- The PSG toxin exhibited commendable antibacterial activity against tested bacterial strains.

Toxins from the posterior salivary gland (PSG) of cuttlefishes are known toxins with pronounced toxicity. In the present study, ionic peptide rich PSG toxin from the cuttlefish S. pharaonis was isolated by ion exchange chromatography and purified by Reversed Phase High Performance Liquid Chromatography (RP-HPLC), with active fraction at a retention time of 26 min. The net protein content of the PSG toxin was estimated to be 46.6 mg at a proximate molecular weight of ∼ 50 kDa. Fourier Transform Infrared Spectroscopy (FT-IR) of PSG toxin revealed the presence of alcoholic OH, primary NH, alkyl CH and conjugated CONH functional groups. Circular Dichroism (CD) spectroscopy and K2D analysis of the PSG toxin confirmed the presence of secondary structure with 36.77% α-helix,12.31% β sheet and 50.92% random coil. Scanning Electron Microscopy (SEM) of the PSG toxin eluted amberlite IRA 900 Cl− resin showed surface abrasion and corrosive blebbing. Energy Dispersive X-ray Spectrometry (EDX) analysis of PSG toxin treated resin revealed increase in nitrogen and sulphur content corresponding to amino acid composition. Teratogenicity of PSG toxin against Zebrafish embryo demonstrated developmental malformations and premature hatching at a maximum tolerated dose of 1.25 μM. The PSG toxin (50 μM) exhibited commendable inhibitory activity with pronounced zone of inhibition against gram E. coli (10 mm) and K. pneumonia (10 mm). The results strongly demonstrate the toxicity of the ionic peptide rich PSG toxin from S. pharaonis and its exploitation for its promise as a potential antibacterial agent of the future.

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