This collection of cyclic polyether natural products (CASs = 98225-48-0 and 98112-41-5; Symbol: Btx or PbTx-2) from the dinoflagellate Karenia brevis consists of neurotoxins that bind to voltage-gated sodium channels, giving rise to neurotoxic shellfish poisoning. Symptoms include nausea, vomiting, slurred speech. Brevetoxins bind at a common binding site (i.e., receptor-site 5) on the a-subunit of this neuronal transmembrane protein. Once bound, the sodium channels remain permanently opened, at the resting membrane potential, which produces a continuous entry of sodium ions in most excitable cells. Such a sodium entry has various consequences on sodiumdependent physiological mechanisms, consisting in a membrane depolarization that, in turn, causes spontaneous and/or repetitive action potential discharges and thereby increases membrane excitability. These neuronal discharges may be transient or continuous depending on the preparation and the toxin tested. Brevetoxin Types: Btx-1 (or PbTx-1) = Btx A + R = –CH2C(=CH2)CHO, FW = 853.05 g/mol; Btx-2 (or PbTx-2) = Btx B + R = –CH2C(=CH2)CHO, FW = 881.06 g/mol; Btx-3 (or PbTx-3) = Btx B + R = –CH2C(=CH2)CH2OH, FW = 852.98 g/mol; Btx-5 (or PbTx- 5) = Btx B (acetylated at Position-38) + R = –CH2C(=CH2)CH2OH, FW = 895.04 g/mol; Btx-6 (or PbTx-6) = Btx B (epoxide in place of double-bond at C27 & C28) + R = –CH2C(=CH2)CH2OH, FW = 897.06 g/mol; Btx-7 (or PbTx-7) = Btx A + R = –CH2C(=CH2)CH2OH, FW = 855.07 g/mol; Btx-8 (or PbTx-8) = Btx B + R = CH2COCH2Cl, FW = 903.50 g/mol; Btx-9 (or PbTx-9) = Btx B + R = –CH2CH(CH3)CH2OH, FW = 885.09 g/mol; and Btx-10 (or PbTx-10) = Btx A + R = –CH2CH(-CH3)CH2OH, FW = 857.08 g/mol.
