Nodularin-Har: a new nodularin from Nodularia

Area of Science:

• Marine Biology
• Toxicology
• Natural Product Chemistry

Background:

• Cyanobacteria are prolific producers of diverse secondary metabolites.
• Hepatotoxins, such as nodularins, pose risks to aquatic ecosystems and human health.
• The structural diversity of nodularins is linked to variations in amino acid residues.

Purpose of the Study:

• To isolate and characterize a novel nodularin analogue from the cyanobacterium Nodularia PCC7804.
• To elucidate the chemical structure of the isolated hepatotoxin.
• To determine the acute toxicity of the novel compound.

Main Methods:

• Isolation of the cyanotoxin using chromatographic techniques.
• Structure elucidation employing 2D Nuclear Magnetic Resonance (2D NMR) and Fast Atom Bombardment Mass Spectrometry (FABMS).
• Determination of median lethal dose (LD50) in a mouse intraperitoneal injection model.

Main Results:

• A novel cyclic peptide hepatotoxin, designated nodularin-Har, was isolated from Nodularia PCC7804.
• The structure of nodularin-Har was confirmed to possess a homoarginine residue in place of the arginine found in other nodularins.
• The LD50 value for nodularin-Har in mice was determined to be 70 microg/kg, indicating significant toxicity.

Conclusions:

• Nodularia PCC7804 produces a structurally distinct hepatotoxin, nodularin-Har.
• The presence of homoarginine influences the toxicological profile of nodularins.
• Nodularin-Har represents a potent cyanobacterial toxin requiring further investigation for ecological and health implications.