This anteiso-heptadecanoic methyl ester is ideal for use as a standard in the verification of samples.1 Many types of bacteria and marine organisms produce anteiso fatty acids which can be used to characterize the various organisms.2 anteiso-Fatty acids, especially anteiso-heptadecanoic acid, are also found in ruminant animals (from the rumen microorganisms) and in ruminant milk. Branched chain fatty acids have been found in the gut of newborn animals where they have a role in the microorganism gut colonization.3 anteiso-Heptadecanoic acid is found in a very few plant species such as in the pine seed oil of Pinaceae.