4-Aminobenzoic acid (also known as ''para''-aminobenzoic acid or PABA because the two functional groups are attached to the
benzene ring across from one another in the ''para'' position) is an
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...
with the
formula H
2NC
6H
4CO
2H. PABA is a white solid, although commercial samples can appear gray. It is slightly soluble in water. It consists of a
benzene ring substituted with
amino and
carboxyl groups. The compound occurs extensively in the natural world.
Production and occurrence
In industry, PABA is prepared mainly by two routes:
* Reduction of
4-nitrobenzoic acid
*
Hoffman degradation
The Hofmann rearrangement (Hofmann degradation) is the organic chemistry, organic reaction of a primary amide to a primary amine with one fewer carbon atom. The reaction involves organic oxidation, oxidation of the nitrogen followed by rearrangem ...
of the monoamide derived from
terephthalic acid.
Food sources of PABA include liver, brewer's yeast (and unfiltered beer), kidney, molasses, mushrooms, and whole grains.
A review on this compound.
Biology
Biochemistry
PABA is an intermediate in the synthesis of
folate by bacteria, plants, and fungi.
Many bacteria, including those found in the human intestinal tract such as
''E. coli'', generate PABA from
chorismate by the combined action of the enzymes
4-amino-4-deoxychorismate synthase and
4-amino-4-deoxychorismate lyase. Plants produce PABA in their chloroplasts, and store it as a glucose ester (''p''ABA-Glc) in their tissues. Humans lack the enzymes to convert PABA to folate and so require folate from dietary sources, such as green leafy vegetables. In humans, PABA is considered nonessential and, although it has been referred to historically as "vitamin B
x", is no longer recognized as a
vitamin