Isopimaric acid

Isopimaric acid (IPA) is a toxin which acts as a large conductance Ca²⁺-activated K⁺ channel (BK channel) opener.

Isopimaric acid

Names
IUPAC name (13S)-Pimara-7,15-dien-18-oic acid
Systematic IUPAC name (1R,4aR,4bS,7S,10aR)-7-Ethenyl-1,4a,7-trimethyl-1,2,3,4,4a,4b,5,6,7,8,10,10a-dodecahydrophenanthrene-1-carboxylic acid
Identifiers
CAS Number	5835-26-7 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:6039 N
ChEMBL	ChEMBL512164 N
ChemSpider	390596 N
ECHA InfoCard	100.163.144
KEGG	C09118 N
PubChem CID	442048
UNII	1E37K85HHK Y
CompTox Dashboard (EPA)	DTXSID9022233
InChI InChI=1S/C20H30O2/c1-5-18(2)12-9-15-14(13-18)7-8-16-19(15,3)10-6-11-20(16,4)17(21)22/h5,7,15-16H,1,6,8-13H2,2-4H3,(H,21,22)/t15-,16+,18-,19+,20+/m0/s1 N Key: MXYATHGRPJZBNA-KRFUXDQASA-N N InChI=1/C20H30O2/c1-5-18(2)12-9-15-14(13-18)7-8-16-19(15,3)10-6-11-20(16,4)17(21)22/h5,7,15-16H,1,6,8-13H2,2-4H3,(H,21,22)/t15-,16+,18-,19+,20+/m0/s1 Key: MXYATHGRPJZBNA-KRFUXDQABR
SMILES [H][C@]12[C@](C)(C(O)=O)CCC[C@]1(C)[C@]3([H])C(C[C@](C=C)(C)CC3)=CC2
Properties
Chemical formula	C20H30O2
Molar mass	302.458 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Sources

IPA originates from many sorts of trees, especially conifers.^[1]

Chemistry

IPA is one of the members of the resin acid group and it is a tricyclic diterpene.^[1]

Target

IPA acts on the large-conductance calcium activated K+ channels (BK channels).^[2][3]

Mode of action

BK channels are formed by α subunits and accessory β subunits arranged in tetramers. The α subunit forms the ion conduction pore and the β subunit contributes to channel gating. IPA interaction with the BK channel enhances Ca²⁺ and / or voltage sensitivity of the α subunit of BK channels without affecting the channel conductance. In this state BK channels can still be inhibited by one of their inhibitors, like charybdotoxin (CTX).^[2][3] Opening of the BK channel leads to an increased K⁺-efflux which hyperpolarizes the resting membrane potential, reducing the excitability of the cell in which the BK-channel is expressed.

Toxicity

Studies on rainbow trout hepatocytes have shown that IPA increases intracellular calcium release, leading to a disturbance in the calcium homeostasis. This could be important in the possible toxicity of the toxin.

See also

• Pimaric acid