4-Aminobenzoic acid

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4-Aminobenzoic acid
4-Aminobenzoic acid.svg
C=black, H=white, O=red, N=blue 4-Aminobenzoic-acid-3D-balls.png
C=black, H=white, O=red, N=blue
Names
Preferred IUPAC name
4-Aminobenzoic acid
Other names
para-Aminobenzoic acid
p-Aminobenzoic acid
PABA
Vitamin B10
Vitamin Bx
Bacterial vitamin H1
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.005.231 OOjs UI icon edit-ltr-progressive.svg
KEGG
PubChem CID
UNII
  • InChI=1S/C7H7NO2/c8-6-3-1-5(2-4-6)7(9)10/h1-4H,8H2,(H,9,10) Yes check.svgY
    Key: ALYNCZNDIQEVRV-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C7H7NO2/c8-6-3-1-5(2-4-6)7(9)10/h1-4H,8H2,(H,9,10)
    Key: ALYNCZNDIQEVRV-UHFFFAOYAH
  • O=C(O)c1ccc(N)cc1
Properties
C7H7NO2
Molar mass 137.138 g·mol−1
AppearanceWhite-grey crystals
Density 1.374 g/mL
Melting point 187 to 189 °C (369 to 372 °F; 460 to 462 K)
Boiling point 340 °C (644 °F; 613 K)
1 g/170 mL (25 °C)
1 g/90 mL (90 °C)
Acidity (pKa)
  • 2.42 (amino; H2O)
  • 4.88 (carboxyl; H2O) [1] [2]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
eye irritant, some persons may be allergic to this compound
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

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 with the formula H2NC6H4CO2H. 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.

Contents

Production and occurrence

In industry, PABA is prepared mainly by two routes:

Food sources of PABA include liver, brewer's yeast (and unfiltered beer), kidney, molasses, mushrooms, and whole grains. [4] Other food sources of PABA include spinach, liver, and oat seeds. [5]

Biology

Biochemistry

Tetrahydrofolate synthesis pathway THFsynthesispathway.png
Tetrahydrofolate synthesis pathway

PABA is an intermediate in the synthesis of folate by bacteria, plants, and fungi. [6] 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. [7] Plants produce PABA in their chloroplasts, and store it as a glucose ester (pABA-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 Bx", is no longer recognized as a vitamin [6] because the typical human gut microbiome generates PABA on its own.

Sulfonamide drugs are structurally similar to PABA, and their antibacterial activity is due to their ability to interfere with the conversion of PABA to folate by the enzyme dihydropteroate synthetase. Thus, bacterial growth is limited through folate deficiency. [8]

Medical use

The potassium salt is used as a drug against fibrotic skin disorders, such as Peyronie's disease, under the brand name Potaba. [9] 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 derivatives have also been proposed to function as acetylcholinesterase inhibitors in diseases that cause deficient cholinergic systems, such as Alzheimer's Disease. [10]

Nutritional supplement

Despite the lack of any recognized syndromes of PABA deficiency in humans, except for those who lack the colonic bacteria that generate PABA, many claims of benefit are made by commercial suppliers of PABA as a nutritional supplement. The benefit is claimed for fatigue, irritability, depression, weeping eczema (moist eczema), scleroderma (premature hardening of the skin), patchy pigment loss in the skin (vitiligo), and premature grey hair. [11]

Commercial and industrial use

PABA finds use in the biomedical sector. Its derivatives are found as a structural component in 1.5% of a database of 12111 commercial drugs. [12] Other uses include its conversion to specialty azo dyes and crosslinking agents. PABA is also used as a biodegradable pesticide, though its use is now limited due to evolution of new variants of bio-pesticides. Specifically, studies have shown that PABA photodegrades through an O2-mediated pathway in which PABA is oxidized by O2 via hydrogen abstraction and decarboxylation. [13]

In the past, PABA was widely used in sunscreens as a UV filter. It is a UVB absorber, meaning it can absorb wavelengths between 290 and 320 nm. [14] while still allowing UVA wavelengths between 320-400 nm to pass through, producing a tan. [15] Patented in 1943, PABA was one of the first active ingredients to be used in sunscreen. [16] The first in vivo studies on mice showed that PABA reduced UV damage. In addition, it was shown to protect against skin tumors in rodents. [17] Animal and in vitro studies in the early 1980s suggested PABA might increase the risk of cellular UV damage. [18] On the basis of these studies, as well as problems with allergies and clothing discoloration, PABA fell out of favor as a sunscreen. However, water-insoluble PABA derivatives such as padimate O are currently used in some cosmetic products including mascara, concealer, and matte lipsticks. [19]

As of 2008, the advancement of new sunscreen is focused on developing a broad spectrum of active ingredients that provide consistent protection across all wavelengths, including UVA. Researchers are considering the PABA–TiO2 Hybrid Nanostructures that result from the method of aqueous in situ synthesis with PABA and TiO2. [15]

Safety considerations

PABA is largely nontoxic; the median lethal dose of PABA in dogs (oral) is 2 g/kg. [3] Allergic reactions to PABA can occur. It is formed in the metabolism of certain ester local anesthetics, and many allergic reactions to local anesthetics are the result of reactions to PABA. [20]

Related Research Articles

<span class="mw-page-title-main">Sunscreen</span> Topical skin product that helps protect against sunburn

Sunscreen, also known as sunblock or sun cream, is a photoprotective topical product for the skin that helps protect against sunburn and most importantly prevent skin cancer. Sunscreens come as lotions, sprays, gels, foams, sticks, powders and other topical products. Sunscreens are common supplements to clothing, particularly sunglasses, sunhats and special sun protective clothing, and other forms of photoprotection.

<span class="mw-page-title-main">Procaine</span> Local anesthetic drug

Procaine is a local anesthetic drug of the amino ester group. It is most commonly used in dental procedures to numb the area around a tooth and is also used to reduce the pain of intramuscular injection of penicillin. Owing to the ubiquity of the trade name Novocain or Novocaine, in some regions, procaine is referred to generically as novocaine. It acts mainly as a sodium channel blocker. Today, it is used therapeutically in some countries due to its sympatholytic, anti-inflammatory, perfusion-enhancing, and mood-enhancing effects.

B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism and synthesis of red blood cells. They are a chemically diverse class of compounds, but are associated in diet, often occurring together in the same foods. Dietary supplements containing all eight are referred to as a vitamin B complex. Individual B vitamins are referred to by B-number or by chemical name, such as B1 for thiamine, B2 for riboflavin, and B3 for niacin, while some are more commonly recognized by name than by number, such as pantothenic acid (B5), biotin (B7), and folate (B9).

<span class="mw-page-title-main">Benzocaine</span> Local anaesthetic drug

Benzocaine, sold under the brand name Orajel amongst others, is a local anesthetic, belonging to the amino ester drug class, commonly used as a topical painkiller or in cough drops. It is the active ingredient in many over-the-counter anesthetic ointments such as products for oral ulcers. It is combined with antipyrine to form A/B ear drops. In the US, products containing benzocaine for oral application are contraindicated in children younger than two years old. In the European Union, the contraindication applies to children under 12 years of age.

<span class="mw-page-title-main">Bumetanide</span> A loop diuretic

Bumetanide, sold under the brand name Bumex among others, is a medication used to treat swelling and high blood pressure. This includes swelling as a result of heart failure, liver failure, or kidney problems. It may work for swelling when other medications have not. For high blood pressure it is not a preferred treatment. It is taken by mouth, or by injection into a vein or muscle. Effects generally begin within an hour and lasts for about six hours.

<span class="mw-page-title-main">Sulfamethoxazole</span> Chemical compound

Sulfamethoxazole is an antibiotic. It is used for bacterial infections such as urinary tract infections, bronchitis, and prostatitis and is effective against both gram negative and positive bacteria such as Escherichia coli and Listeria monocytogenes.

Benzonatate, sold under the brand name Tessalon among others, is a medication that is used for the symptomatic relief of cough. A 2023 systematic review found that there is inadequate evidence to support the effectiveness and safety of benzonatate for cough and highlighted rising safety concerns. Benzonatate is taken by mouth. Effects generally begin within 20 minutes and last 3 to 8 hours.

<span class="mw-page-title-main">Chorismic acid</span> Chemical compound

Chorismic acid, more commonly known as its anionic form chorismate, is an important biochemical intermediate in plants and microorganisms. It is a precursor for:

<span class="mw-page-title-main">UV filter</span> Camera parts, features and technologies

UV filters are compounds, mixtures, or materials that block or absorb ultraviolet (UV) light. One of the major applications of UV filters is their use as sunscreens to protect skin from sunburn and other sun/UV related damage. After the invention of digital cameras changed the field of photography, UV filters have been used to coat glass discs fitted to camera lenses to protect hardware that is sensitive to UV light.

<span class="mw-page-title-main">Padimate O</span> Water-insoluble oily ingredient used in some sunscreens

Padimate O is an organic compound related to the water-soluble compound PABA that is used as an ingredient in some sunscreens. This yellowish water-insoluble oily liquid is an ester formed by the condensation of 2-ethylhexanol with dimethylaminobenzoic acid. Other names for padimate O include 2-ethylhexyl 4-dimethylaminobenzoate, Escalol 507, octyldimethyl PABA, and OD-PABA.

<span class="mw-page-title-main">Sulfanilamide</span> Chemical compound

Sulfanilamide is a sulfonamide antibacterial drug. Chemically, it is an organic compound consisting of an aniline derivatized with a sulfonamide group. Powdered sulfanilamide was used by the Allies in World War II to reduce infection rates and contributed to a dramatic reduction in mortality rates compared to previous wars. Sulfanilamide is rarely if ever used systemically due to toxicity and because more effective sulfonamides are available for this purpose. Modern antibiotics have supplanted sulfanilamide on the battlefield; however, sulfanilamide remains in use today in the form of topical preparations, primarily for treatment of vaginal yeast infections--mainly vulvovaginitis, which is caused by Candida albicans.

<span class="mw-page-title-main">Sulfacetamide</span> Sulfonamide antibiotic

Sulfacetamide is a sulfonamide antibiotic.

<span class="mw-page-title-main">Dihydropteroate</span> Chemical compound

Dihydropteroate is an important intermediate in folate synthesis. It is a pterin created from para-aminobenzoic acid (PABA) by the enzyme dihydropteroate synthase.

<span class="mw-page-title-main">Dihydropteroate synthase</span> Class of enzymes

Dihydropteroate synthase (DHPS) is an enzyme classified under EC 2.5.1.15. It produces dihydropteroate in bacteria, but it is not expressed in most eukaryotes including humans. This makes it a useful target for sulfonamide antibiotics, which compete with the PABA precursor.

<span class="mw-page-title-main">Tetrahydrofolic acid</span> Chemical compound

Tetrahydrofolic acid (THFA), or tetrahydrofolate, is a folic acid derivative.

4-amino-4-deoxychorismate lyase is an enzyme that participates in folate biosynthesis by catalyzing the production of PABA by the following reaction

<span class="mw-page-title-main">Aminodeoxychorismate synthase</span>

In enzymology, an aminodeoxychorismate synthase is an enzyme that catalyzes the chemical reaction

<span class="mw-page-title-main">2-Chlorobenzoic acid</span> Chemical compound

2-Chlorobenzoic acid is an organic compound with the formula ClC6H4CO2H. It is one of three isomeric chlorobenzoic acids, the one that is the strongest acid. This white solid is used as a precursor to a variety of drugs, food additives, and dyes.

<span class="mw-page-title-main">Sunburn</span> Burning of the skin by the suns radiation

Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, usually from the Sun. Common symptoms in humans and other animals include red or reddish skin that is hot to the touch or painful, general fatigue, and mild dizziness. Other symptoms include blistering, peeling skin, swelling, itching, and nausea. Excessive UV radiation is the leading cause of (primarily) non-malignant skin tumors, which in extreme cases can be life-threatening. Sunburn is an inflammatory response in the tissue triggered by direct DNA damage by UV radiation. When the cells' DNA is overly damaged by UV radiation, type I cell-death is triggered and the tissue is replaced.

Mycosporine-like amino acids (MAAs) are small secondary metabolites produced by organisms that live in environments with high volumes of sunlight, usually marine environments. The exact number of compounds within this class of natural products is yet to be determined, since they have only relatively recently been discovered and novel molecular species are constantly being discovered; however, to date their number is around 30. They are commonly described as “microbial sunscreens” although their function is believed not to be limited to sun protection. MAAs represent high potential in cosmetics, and biotechnological applications. Indeed, their UV-absorbing properties would allow to create products derived from natural photoprotectors, potentially harmless to the environment and efficient against UV damage.

References

  1. ↑ van de Graaf, Bas (1981). "Substituent effects. 7. Microscopic dissociation constants of 4-amino- and 4-(dimethylamino)benzoic acid". J. Org. Chem. 46 (4): 653–657. doi:10.1021/jo00317a002.
  2. ↑ Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. pp. 5–89. ISBN   978-1-4987-5428-6.
  3. 1 2 Maki, T.; Takeda, K. (2000). "Benzoic Acid and Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH. doi:10.1002/14356007.a03_555. ISBN   3-527-30673-0.
  4. ↑ "Nutritional Health Resource". Archived from the original on 2009-12-16. Retrieved 2009-11-21.
  5. ↑ Henry RJ (1943). "The Mode of Action of Sulfonamides". American Society for Microbiology. 7 (4): 175–245. doi: 10.1128/br.7.4.175-262.1943 . PMC   440870 . PMID   16350088.
  6. 1 2 "Para-aminobenzoic acid". Medline Plus Medical Encyclopedia. United States National Institutes of Health . Retrieved 24 January 2014.
  7. ↑ Folate Synthesis (Abstract)
  8. ↑ Brown GM (1962). "The biosynthesis of folic acid. II. Inhibition by sulfonamides". J. Biol. Chem. 237 (2): 536–40. doi: 10.1016/S0021-9258(18)93957-8 . PMID   13873645.
  9. ↑ "Compound Summary on PubChem". PubChem . National Institute of Health: National Library of Medicine. 2006. Retrieved 2006-04-05.
  10. ↑ Correa-Basurto J (2005). "p-Aminobenzoic acid derivatives as acetylcholinesterase inhibitors". Eur. J. Med. Chem. 40 (7): 732–5. doi: 10.1016/j.ejmech.2005.03.011 . PMID   15935907.
  11. ↑ "Health Library (Supplements) PABA". Archived from the original on 2017-08-04. Retrieved 2017-08-04.
  12. ↑ Kluczyk, Alicja; Popek, Tomasz; Kiyota, Taira; de Macedo, Pierre; Stefanowicz, Piotr; Lazar, Carmen; Konishi, Yasuo (2002). "Drug Evolution: p-Aminobenzoic Acid as a Building Block". Current Medicinal Chemistry. 9 (21): 1871–1892. doi:10.2174/0929867023368872. ISSN   0929-8673. PMID   12369873.
  13. ↑ Zhang S (2016). "Unveiling self-sensitized photodegradation pathways by DFT calculations: A case of sunscreen p-aminobenzoic acid". Chemosphere. 163: 227–33. Bibcode:2016Chmsp.163..227Z. doi: 10.1016/j.chemosphere.2016.08.028 . PMID   27529387.
  14. ↑ Melanoma Madness The scientific flap over sunscreens and skin cancer -- Chemical studies, Science News Online, 6/6/98 (accessed 10/1/2009, 2009)
  15. 1 2 Rahal, R.; Daniele, S.; Hubert-Pfalzgraf, L. G.; Guyot-Ferréol, V.; Tranchant, J (2008). "Synthesis of para-Amino Benzoic Acid–TiO2 Hybrid Nanostructures of Controlled Functionality by an Aqueous One-Step Process". European Journal of Inorganic Chemistry. 2008 (6): 980–987. doi:10.1002/ejic.200700971.
  16. ↑ Gasparro, F. P.; Mitchnick, M.; Nash, J. F. A Review of Sunscreen Safety and Efficacy Photochem. Photobiol. 1998, 68, 243, 256.
  17. ↑ H.; Thune, P.; Eeg Larsen, T. The inhibiting effect of PABA on photocarcinogenesis Arch. Dermatol. Res. 1990, 282, 38, 41.
  18. ↑ Osgood, Pauline J.; Moss, Stephen H.; Davies, David J. G. (1982). "The Sensitization of Near-Ultraviolet Radiation Killing of Mammalian Cells by the Sunscreen Agent Para-aminobenzoic Acid". Journal of Investigative Dermatology. 79 (6): 354–7. doi: 10.1111/1523-1747.ep12529409 . PMID   6982950.
  19. ↑ US 10064810,Stagg, Amanda M; Rubinson, Emily H.,"Matte cosmetic compositions",published September 4, 2018
  20. ↑ Toxicity, Local Anesthetics: eMedicine Emergency Medicine
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