Wikipedia:WikiProject Chemicals/Chembox validation/VerifiedDataSandbox and 4-Aminobenzoic acid: Difference between pages

| Watchedfields = changed

| verifiedrevid = 477220910

| ImageFileL1_Ref = {{chemboximage|correct|??}}

| ImageFileL1 =4-Aminobenzoic acid.svg

| ImageAltL1 = Skeletal formula of PABA

| ImageFileR1 = 4-Aminobenzoic-acid-3D-balls.png

| ImageSizeR1 = 115

| ImageNameR1 = C=black, H=white, O=red, N=blue

| ImageAltR1 = Ball-and-stick model of the PABA molecule

| PIN = 4-Aminobenzoic acid

| OtherNames =''para''-Aminobenzoic acid<br />''p''-Aminobenzoic acid<br />PABA<br />Vitamin B₁₀<br />Vitamin B_x<br />Bacterial vitamin H¹

|Section1={{Chembox Identifiers

| UNII_Ref = {{fdacite|correct|FDA}}

| InChIKey = ALYNCZNDIQEVRV-UHFFFAOYAH

| ChEMBL_Ref = {{ebicite|correct|EBI}}

| CASNo =150-13-0

| PubChem =978

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChEBI_Ref = {{ebicite|correct|EBI}}

|Section2={{Chembox Properties

| C=7 | H=7 | N=1 | O=2

| Appearance = White-grey crystals

| Density =1.374 g/mL

| MeltingPtC = 187 to 189

| MeltingPt_notes =

| BoilingPtC = 340

| BoilingPt_notes =

| Solubility =1 g/170 mL (25 °C)<br/>1 g/90 mL (90 °C)

| pKa = {{ubl

| 2.42 (amino; H₂O)

| 4.88 (carboxyl; H₂O)<ref>{{cite journal |last1=van de Graaf |first1=Bas |title=Substituent effects. 7. Microscopic dissociation constants of 4-amino- and 4-(dimethylamino)benzoic acid |journal=J. Org. Chem. |date=1981 |volume=46 |issue=4 |pages=653–657 |doi=10.1021/jo00317a002 |url=https://pubs.acs.org/doi/pdfplus/10.1021/jo00317a002}}</ref><ref name="CRC97">{{cite book | editor= Haynes, William M. | year = 2016 | title = CRC Handbook of Chemistry and Physics | edition = 97th | publisher = [[CRC Press]] | isbn = 978-1-4987-5428-6 | pages=5–89 | title-link = CRC Handbook of Chemistry and Physics }}</ref>

}}

|Section3={{Chembox Hazards

| MainHazards = eye irritant, some persons may be allergic to this compound

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| Section6 = {{Chembox Pharmacology

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'''4-Aminobenzoic acid''' (also known as ''para''-aminobenzoic acid or '''PABA''' because the two [[functional group]]s are attached to the [[benzene ring]] across from one another in the ''para'' position) is an [[organic compound]] with the [[chemical formula|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 [[amine|amino]] and [[carboxyl group]]s. 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|4-nitrobenzoic acid]]

* [[Hoffman degradation]] of the monoamide derived from [[terephthalic acid]].<ref name=Ullmann>{{Cite book | last1 = Maki | first1 = T. | last2 = Takeda | first2 = K. | year = 2000| chapter = Benzoic Acid and Derivatives | title = Ullmann's Encyclopedia of Industrial Chemistry| publisher = [[Wiley-VCH]]| doi = 10.1002/14356007.a03_555| isbn = 3-527-30673-0 }}</ref>

Food sources of PABA include liver, brewer's yeast (and unfiltered beer), kidney, molasses, mushrooms, and whole grains.<ref>{{Cite web |url=http://www.healthsupplementsnutritionalguide.com/PABA.html#FOODS |title=Nutritional Health Resource |access-date=2009-11-21 |archive-url=https://web.archive.org/web/20091216224758/http://www.healthsupplementsnutritionalguide.com/PABA.html#FOODS |archive-date=2009-12-16 |url-status=dead }}</ref> Other food sources of PABA include spinach, liver, and oat seeds.<ref>{{cite journal | author = Henry RJ| date = 1943 | title = The Mode of Action of Sulfonamides | journal = American Society for Microbiology | volume = 7 | pages = 175–245 | issue = 4 | doi = 10.1128/br.7.4.175-262.1943 | doi-access = free | pmid = 16350088 | pmc = 440870 }}</ref>

==Biology==

===Biochemistry===

[[Image:THFsynthesispathway.png|thumb|400px|[[Tetrahydrofolate]] synthesis pathway]]

PABA is an intermediate in the synthesis of [[folate]] by bacteria, plants, and fungi.<ref name=MedlinePlus>{{cite encyclopedia | title=Para-aminobenzoic acid | encyclopedia=Medline Plus Medical Encyclopedia | url=https://www.nlm.nih.gov/medlineplus/ency/article/002518.htm | publisher=United States [[National Institutes of Health]] | access-date=24 January 2014 }}</ref>

Many bacteria, including those found in the human intestinal tract such as [[Escherichia coli|''E. coli'']], generate PABA from [[chorismate]] by the combined action of the enzymes [[Aminodeoxychorismate synthase|4-amino-4-deoxychorismate synthase]] and [[Aminodeoxychorismate lyase|4-amino-4-deoxychorismate lyase]].<ref>[http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=341757 Folate Synthesis (Abstract)]</ref> 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]]<ref name=MedlinePlus/> because the typical human gut [[microbiome]] generates PABA on its own.

[[Sulfonamide (medicine)|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.<ref>{{cite journal | author = Brown GM | date = 1962 | title = The biosynthesis of folic acid. II. Inhibition by sulfonamides | journal = J. Biol. Chem. | volume = 237 | pages = 536–40 | pmid = 13873645 | issue = 2 | doi = 10.1016/S0021-9258(18)93957-8 | doi-access = free }}</ref>

===Medical use===

The potassium salt is used as a drug against fibrotic skin disorders, such as [[Peyronie's disease]], under the brand name Potaba.<ref name=PubChem>

{{cite web

| year = 2006

| url = https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=978

| title = Compound Summary on PubChem

| work = [[PubChem]]

| publisher = National Institute of Health: National Library of Medicine

| access-date = 2006-04-05

}}</ref> 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.<ref>{{cite journal | author = Correa-Basurto J| date = 2005 | title = p-Aminobenzoic acid derivatives as acetylcholinesterase inhibitors | journal = Eur. J. Med. Chem. | volume = 40 | pages = 732–5 | pmid = 15935907 | issue = 7 | doi = 10.1016/j.ejmech.2005.03.011 | doi-access = free }}</ref>

===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.<ref>{{Cite web |url=http://healthlibrary.epnet.com/GetContent.aspx?token=5b000b40-3809-4cb2-88a4-68bfd31b5c51&chunkiid=21831 |title=Health Library (Supplements) PABA |access-date=2017-08-04 |archive-url=https://web.archive.org/web/20170804174706/http://healthlibrary.epnet.com/GetContent.aspx?token=5b000b40-3809-4cb2-88a4-68bfd31b5c51&chunkiid=21831 |archive-date=2017-08-04 |url-status=live }}</ref>

==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.<ref name="KluczykPopek2002">{{cite journal|last1=Kluczyk|first1=Alicja|last2=Popek|first2=Tomasz|last3=Kiyota|first3=Taira|last4=de Macedo|first4=Pierre|last5=Stefanowicz|first5=Piotr|last6=Lazar|first6=Carmen|last7=Konishi|first7=Yasuo|title=Drug Evolution: p-Aminobenzoic Acid as a Building Block|journal=Current Medicinal Chemistry|volume=9|issue=21|year=2002|pages=1871–1892|issn=0929-8673|doi=10.2174/0929867023368872|pmid=12369873}}</ref> Other uses include its conversion to specialty [[azo dye]]s and [[crosslinking agent]]s. 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 O<small>2</small>-mediated pathway in which PABA is oxidized by O<small>2</small> via hydrogen abstraction and decarboxylation.<ref>{{cite journal | author = Zhang S| date = 2016 | title = Unveiling self-sensitized photodegradation pathways by DFT calculations: A case of sunscreen p-aminobenzoic acid | journal = Chemosphere | volume = 163 | pages = 227–33 | doi = 10.1016/j.chemosphere.2016.08.028 | doi-access = free | pmid = 27529387 | bibcode = 2016Chmsp.163..227Z }}</ref>

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&nbsp;nm.<ref>[http://www.sciencenews.org/pages/sn_arc98/6_6_98/bob2.htm Melanoma Madness The scientific flap over sunscreens and skin cancer -- Chemical studies], Science News Online, 6/6/98 (accessed 10/1/2009, 2009)</ref> while still allowing UVA wavelengths between 320-400&nbsp;nm to pass through, producing a tan.<ref name="Rahal, R. 2008 980–987">{{cite journal |author=Rahal, R. |author2=Daniele, S. |author3=Hubert-Pfalzgraf, L. G. |author4=Guyot-Ferréol, V. |author5=Tranchant, J| date =2008 | title = Synthesis of para-Amino Benzoic Acid–TiO₂ Hybrid Nanostructures of Controlled Functionality by an Aqueous One-Step Process.| journal = European Journal of Inorganic Chemistry | volume = 2008 | pages = 980–987 | issue = 6| doi =10.1002/ejic.200700971 }}</ref>

Patented in 1943, PABA was one of the first active ingredients to be used in [[sunscreen]].<ref>Gasparro, F. P.; Mitchnick, M.; Nash, J. F. A Review of Sunscreen Safety and Efficacy Photochem. Photobiol. 1998, 68, 243, 256.</ref> 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.<ref name=Hansen,>H.; Thune, P.; Eeg Larsen, T. The inhibiting effect of PABA on photocarcinogenesis Arch. Dermatol. Res. 1990, 282, 38, 41.</ref>

Animal and ''in vitro'' studies in the early 1980s suggested PABA might increase the risk of cellular UV damage.<ref name=Sensitization>{{cite journal | last1 = Osgood | first1 = Pauline J. | last2 = Moss | first2 = Stephen H. | last3 = Davies | first3 = David J. G. | title = The Sensitization of Near-Ultraviolet Radiation Killing of Mammalian Cells by the Sunscreen Agent Para-aminobenzoic Acid | journal = Journal of Investigative Dermatology | volume = 79 | issue = 6 | pages = 354–7 | year = 1982 | pmid = 6982950 | doi = 10.1111/1523-1747.ep12529409| doi-access = free }}</ref> 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.<ref>{{cite patent | inventor= Stagg, Amanda M; Rubinson, Emily H.| pubdate = September 4, 2018 | title = Matte cosmetic compositions| number = 10064810| country= US}}</ref>

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.<ref name="Rahal, R. 2008 980–987"/>

==Safety considerations==

PABA is largely nontoxic; the [[median lethal dose]] of PABA in dogs (oral) is 2 g/kg.<ref name=Ullmann/> 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.<ref>[http://emedicine.medscape.com/article/819628-overview Toxicity, Local Anesthetics: eMedicine Emergency Medicine<!-- Bot generated title -->]</ref>

==References==

{{reflist}}

{{Other dermatological preparations}}

{{Sunscreening agents}}

{{DEFAULTSORT:Aminobenzoic Acid, 4-}}

[[Category:Anilines]]

[[Category:Benzoic acids]]

[[Category:IARC Group 3 carcinogens]]

[[Category:Sunscreening agents]]

[[Category:Non-proteinogenic amino acids]]