3-hydroxy Undecanoic acid is a hydroxylated fatty acid that has been found in S. algae, LPS extracted from clinical isolates of B. catarrhalis, and methyl-branched poly(3-hydroxyalkanoate) (PHA) polymers produced by P. flava isolated from oil-contaminated soil. It inhibits sodium current in axons dissected from mantles of giant squid (D. bleekeri) with an ED50 value of 0.46 mM.