Okadaic acid

January 29, 2024
Don’t eat seafood that might contain me!
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Okadaic acid1, a nasty marine toxin, is a complex multiring polyether found in certain dinoflagellates, single-cell eukaryotes of the genera Dinophysis and Thorecta. It typically accumulates in sea sponges and shellfish. It was first discovered and characterized in 1981 by Paul J. Scheuer, Jon Clardy, Francis J. Schmitz, and collaborators at the University of Hawaii at Manoa (Honolulu), Fujisawa Pharmaceutical (Tokyo), Cornell University (Ithaca, NY), and the University of Oklahoma (Norman) in the sponges Halichondria okadai (for which it was named) and H. melandocia.

Okadaic acid is a potent inhibitor of serine–threonine phosphatase subclasses PP2A, PP1, and PP2B. (PP stands for protein phosphatase.) It is the inhibition of this enzyme that is a primary cause of diarrheic shellfish poisoning (DSP) in humans. In addition to diarrhea, DSP can cause abdominal pain, nausea, and vomiting.

In 2013, Vanessa Valdiglesias and coauthors at the University of A Coruña (Spain) published a review of other harmful effects of okadaic acid. They discussed studies that reported the compound’s role in cytotoxicity, genotoxicity, immunotoxicity, embryotoxicity, neurotoxicity, and carcinogenicity. At that time, no reported data indicated that these toxicities cause chronic or subchronic effects in humans; but the authors believed that more research should be done in this area. On the positive side, they stated that okadaic acid is a useful tool for studying cellular signaling because of its selective inhibition of protein phosphatase activity.

For updated information on okadaic acid, see the molecule’s ScienceDirect page.

1. SciFinder: 1,7-dioxaspiro[5.5]undec-10-ene-2-propanoic acid, α,5-dihydroxy-α,10-dimethyl-8-[(1R,2E)-1-methyl-3-[(2R,4′aR,5R,6′S,8′R,8′aS)-octahydro-8′-hydroxy-6′-[(1S,3S)-1-hydroxy-3-[(2S,3R,6S)-3-methyl-1,7-dioxaspiro[5.5]undec-2-yl]butyl]-7′-methylenespiro[furan-2(3H),2′ (3′H)-pyrano[3,2-b]pyran]-5-yl]-2-propen-1-yl]-, (αR,2S,5R,6R,8S)-.

Okadaic acid hazard information

Hazard class*GHS code and hazard statement
Acute toxicity, oral, category 3H301—Toxic if swallowedChemical Safety Warning
Acute toxicity, dermal, category 3H311—Toxic in contact with skinChemical Safety Warning

Skin corrosion/irritation, category 2

H315—Causes skin irritationChemical Safety Warning

Acute toxicity, inhalation, category 3

H331—Toxic if inhaledChemical Safety Warning

*Globally Harmonized System (GHS) of Classification and Labeling of Chemicals. Explanation of pictograms.

Molecules from the journals

Titanium diboride1 (TiB2) is one of the hardest known ceramic materials, especially in the temperature range 1000–3000 °C. It has other excellent properties, including high thermal and electrical conductivities and the highest elastic modulus, fracture toughness, compressive strength, and melting point of all boride ceramics.

Last month, Satadru Chakrabarty and Kabeer Jasuja* at the Indian Institute of Technology Gandhinagar described another valuable aspect of TiB2. When formed into a gel-like, oxygen-functionalized nanosheet dispersion, it reacts with ascorbic acid2 to change the color of the dispersion from yellow to orange. The reaction also disrupts the cross-links between the borate groups on the nanosheets that are responsible for the gel structure of the dispersion.

Pterodactylane3—tetracyclo[,5.07,10]decane—is a hydrocarbon with four cyclobutane rings connected linearly. It was first synthesized in 1965 by Rangaswamy Srinivasan* and K. A. Hill at the IBM Watson Research Center (Yorktown Heights, NY) via the photolysis of benzene. Although the C4H10 product can exist in three positional isomers, only one isomer was produced.

Pterodactylane is so named because its structure resembles the wings of a pterodactyl in flight. It is also called [4]-ladderane, one of a series of fused cyclobutane molecules whose structures take the shape of a ladder.

In December, Stephen L. Craig, Todd J. Martínez, Yan Xia, and collaborators at Stanford University (CA), Duke University (Durham, NC), and Heinrich Heine University (Düsseldorf, Germany) described the mechanochemistry of pterodactylane. In one study, they prepared pterodactylanes with substituents on the central rung and on the end rung. When they applied outward forces to the substituents, they were surprised to find that the threshold force for bond breaking is dramatically lower for the central rung (0.7 nN) than the end rung (1.9 nN).

1. CAS Reg. No. 12045-63-5.
2. CAS Reg. No. 50-81-7.
3. CAS Reg. No. 4466-29-9.

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Okadaic acid fast facts

CAS Reg. No.78111-17-8
Empirical formulaC44H68O13
Molar mass805.00 g/mol
AppearanceWhite crystals or powder
Melting point164–166 °C
171–174 °Ca
Water solubilityInsoluble

a. Both values appear in the chemical literature.

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