Algal toxins are toxic substances produced by unicellular algae which can pollute fresh and salt water, drinking water and the recreational water, or swimming pools water. They can give rise to accumulation phenomena in mollusks and fish, causing intoxication along the entire food chain and involving cetaceans, birds, other mammals and humans.

Microcystins

Microcystins are cyclic heptapeptides made up of non-proteinogenic amino acids produced by different kind of cyanobacteria (Microcystis, Noduylaria, Oscillatoria). There were identified about a hundred congeners. They are lipophilic toxins very resistant to hydrolysis, high temperatures and oxidation.

These are hepatotoxic toxins, classified as possible carcinogens for humans.

The main route of human exposure is the contaminated drinking water ingestion, in addition to the consumption of contaminated food or accidental exposure through dialysis water. Exposure via the respiratory tract may also play a role.

Cylindrospermopsin

Cylindrospermopsin is a guanidine alkaloid produced by different species of cyanobacteria; among these Cylindrospermopsisraciborskii, is the most widespread in the world.

Cylindrospermopsin is a small hydrophilic toxin capable of partially penetrating biological membranes. It gives accumulation in the liver and kidney.

Human exposure can occur through the ingestion of contaminated drinking water, through contact with recreational water but also through the consumption of contaminated food.

Anatoxin

Anatoxin A is a bicyclic amino alkaloid with a structure similar to cacine, produced by some strains of Anabena and other genera of cyanobacteria (MicrocystisOscillatoria).

Known as “Very Fast Death Factor”, it is a cholinergic agonist of central and peripheral nervous system and in neuromuscular junctions. The symptoms related to anatoxin A intoxication include loss of coordination, muscle contraction, convulsions until death due to respiratory paralysis.

The main route of human exposure consists in the contaminated drinking water intake.

Brevetoxins

Brevetoxins are a family of cyclic polyesthers produced by some dinoflagellates (Gymnodinium breve). Known as "Neurotoxic Shellfish Poisoning", or NSP, they owe their neutoroxic properties to their action of depolarization of cell membranes with consequent opening of sodium channels. The main symptoms are paralysis of the mouth and fingers, slow heart rate, diarrhea.

The risk for humans is the ingestion of contaminated shellfish and inhalation of aerosols. The episodes recorded so far are circumscribed along the coasts of Central America and are not associated with mortality.

Saxitoxin

Saxitoxin is a cyclic non-ribosomal peptide produced by some species of dinoflagellates and cyanobacteria present in fresh and salt water. The toxin, along with its twenty congeners (including neosaxitoxin), gives phenomena of accumulation in mollusks.

Saxitoxin is responsible for the "Paralytic Shellfish Poisoning" syndrome, or PSP: by interacting with ion channels, it interferes with nerve transmission. The symptoms are a tingling in the mouth which extends to the face and then to the whole body, continuing with muscular anesthesia and ataxia until death due to respiratory paralysis at 3-10 hours from ingestion. The mortality rate of saxitoxin is between 1 and 20% and is correlated with the ingested dose. The poisoning is treated with gastric lavage and eventual treatments with alkaline solutions that inactivate the toxin.

Domoic acid

Domoic acid is a cyclic water-soluble amino acid produced by the red marine algae of the genus Chondria and by diatoms of the genus Pseudonitschia.

It is a neurotoxin responsible for the so-called amnesic shellfish poisoning or "Amnesic Shellfish Poisoning"  (ASP): its chemical structure similar to glutamate one leads it to interact with kainate receptors. The symptoms associated with domoic acid poisoning taken through the consumption of contaminated shellfish include short-term memory loss, brain damage and even death in the most serious cases. It may also be involved in liver and gastrointestinal damages.

Ocadaic acid

Okadaic acid (or ocadaic) is a toxin produced by some dinoflagellates (Synophisis spp., Procentrum).

This toxin is among the main causes of "Diarrhetic Shellfish Poisoning", DSP,and it is a powerful inhibitor of protein phosphatase. Okadaic acid is a polyketide, a molecule characterized by a complex structure, whose targets are the phosphatase 1 and 2 proteins (PP1 and PP2). The inhibition of these proteins alters the control of the salt balance within the cell, undermining its permeability. This occurs particularly in the intestinal epithelium, resulting in a poisoning syndrome characterized by diarrhea, nausea, vomiting and cramps.