4-Aminobenzoic acid
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| Names | |
|---|---|
| IUPAC name
4-aminobenzoic acid
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| Other names
para-Aminobenzoic acid
p-Aminobenzoic acid PABA Vitamin Bx Bacterial vitamin H1 | |
| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.005.231 |
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| C7H7NO2 | |
| Molar mass | 137.14 g/mol |
| Appearance | white crystals |
| Density | 1.374 g/mL |
| Melting point | 187–189 °C |
| 1 g/170 mL (25 °C) 1 g/90 mL (90 °C) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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4-Aminobenzoic acid (also known as para-aminobenzoic acid or PABA) is an organic compound with the molecular formula C7H7NO2. PABA is a white crystalline substance that is only slightly soluble in water. It consists of a benzene ring substituted with an amino group and a carboxyl group.
Functions
Organic
PABA is an essential nutrient for some bacteria and is sometimes called Vitamin Bx[1]. In humans, PABA is normally made by E. coli[2] in the colon and therefore PABA from food is not normally essential to human health. PABA is therefore not officially classified as a vitamin. PABA is an intermediate in bacterial synthesis of folate. Although humans lack the ability to synthesize folate from PABA, that is also normally done by E. coli.[3] PABA is sometimes marketed as an essential nutrient for use whenever normal PABA synthesis by intestinal bacteria is insufficient.
Symptoms of PABA deficiency may include general fatigue, irritability, depression, weeping eczema (moist eczema), scleroderma (premature wrinkling of skin), patchy pigment loss in skin (vitiligo), and premature grey hair.[4] Food sources of PABA include liver, brewer's yeast (and unfiltered beer), kidney, molasses, and whole grains.
Sulfonamides are chemically similar to PABA, and their antibacterial activity is due to their ability to interfere with conversion of PABA to folate by dihydropteroate synthetase, and subsequent utilization, by bacteria.
Industrial
In the past, PABA has been widely used as a UV filter in sunscreen formulations. However, it has been determined that it increases the formation of a particular DNA defect in human cells, thus increasing the risk of skin cancer.[5] Currently, safer and more effective derivatives of PABA, such as octyl dimethyl PABA (padimate O), are more commonly used.
The potassium salt is used as a drug against fibrotic skin disorders under the trade name POTABA.[6] PABA is also occasionally used in pill form by sufferers of Irritable bowel syndrome to treat its associated gastrointestinal symptoms, and in nutritional epidemiological studies to assess the completeness of 24-hour urine collection for the determination of urinary sodium, potassium, or nitrogen levels.
PABA also finds use in the manufacture of esters, folic acid, and azo dyes.
See also
References
- ^ "Para-aminobenzoic acid poisoning". National Institute of Health: National Library of Medicine. 2007. Retrieved 2007-06-19.
- ^ Folate Synthesis (Abstract)
- ^ In vivo Folate Production
- ^ Vitamin Deficiency Guide
- ^
P. J. Osgood (1982). "The sensitization of near-ultraviolet radiation killing of mammalian cells by the sunscreen agent para-aminobenzoic acid". Journal of Investigative Dermatology. 79 (6): 354–357. doi:10.1111/1523-1747.ep12529409.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ "Compound Summary on PubChem". PubChem. National Institute of Health: National Library of Medicine. 2006. Retrieved 2006-04-05.