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Revision as of 18:06, 16 February 2012 editBeetstra (talk | contribs)Edit filter managers, Administrators172,031 edits Saving copy of the {{chembox}} taken from revid 477210444 of page 4-Aminobenzoic_acid for the Chem/Drugbox validation project (updated: '').  Latest revision as of 02:02, 17 December 2024 edit Arthurfragoso (talk | contribs)Extended confirmed users2,003 edits Fixes images on dark mode 
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{{ambox | text = This page contains a copy of the infobox ({{tl|chembox}}) taken from revid of page ] with values updated to verified values.}}
{{chembox {{chembox
| Watchedfields = changed
| verifiedrevid = 443654329
| verifiedrevid = 477220910
| ImageFile_Ref = {{chemboximage|correct|??}}
| ImageFileL1_Ref = {{chemboximage|correct|??}}
| ImageFile=4-Aminobenzoic acid.svg
| ImageFileL1 =4-Aminobenzoic acid.svg
|ImageSize=100px
| ImageClassL1 = skin-invert
|IUPACName=4-Aminobenzoic acid
| ImageAltL1 = Skeletal formula of PABA
|OtherNames=''para''-Aminobenzoic acid; ''p''-Aminobenzoic acid; PABA; Vitamin B<sub>x</sub>; Bacterial vitamin H<sup>1</sup>
| ImageFileR1 = 4-Aminobenzoic-acid-3D-balls.png
|Section1= {{Chembox Identifiers
| ImageSizeR1 = 115
| UNII_Ref = {{fdacite|correct|FDA}}
| 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 B<sub>10</sub><br />Vitamin B<sub>x</sub><br />Bacterial vitamin H<sup>1</sup>
|Section1={{Chembox Identifiers
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = TL2TJE8QTX | UNII = TL2TJE8QTX
| KEGG_Ref = {{keggcite|correct|kegg}} | KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D02456 | KEGG = D02456
| InChI = 1/C7H7NO2/c8-6-3-1-5(2-4-6)7(9)10/h1-4H,8H2,(H,9,10) | InChI = 1/C7H7NO2/c8-6-3-1-5(2-4-6)7(9)10/h1-4H,8H2,(H,9,10)
| InChIKey = ALYNCZNDIQEVRV-UHFFFAOYAH | InChIKey = ALYNCZNDIQEVRV-UHFFFAOYAH
| ChEMBL_Ref = {{ebicite|correct|EBI}} | ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 542 | ChEMBL = 542
| StdInChI_Ref = {{stdinchicite|correct|chemspider}} | StdInChI_Ref = {{stdinchicite|correct|chemspider}}
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| StdInChIKey = ALYNCZNDIQEVRV-UHFFFAOYSA-N | StdInChIKey = ALYNCZNDIQEVRV-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}} | CASNo_Ref = {{cascite|correct|CAS}}
| CASNo=150-13-0 | CASNo =150-13-0
| PubChem=978 | PubChem =978
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 953 | ChemSpiderID = 953
| ChEBI_Ref = {{ebicite|correct|EBI}} | ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 30753 | ChEBI = 30753
| DrugBank_Ref = {{drugbankcite|correct|drugbank}} | DrugBank_Ref = {{drugbankcite|correct|drugbank}}
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| SMILES = O=C(O)c1ccc(N)cc1 | SMILES = O=C(O)c1ccc(N)cc1
}} }}
|Section2= {{Chembox Properties |Section2={{Chembox Properties
| C=7|H=7|N=1|O=2 | C=7 | H=7 | N=1 | O=2
| Appearance= White-grey crystals | Appearance = White-grey crystals
| Density=1.374 g/mL | Density =1.374 g/mL
| MeltingPtC = 187 to 189
| MeltingPt=187–189 °C
| MeltingPt_notes =
| BoilingPt=
| BoilingPtC = 340
| Solubility=1 g/170 mL (25 °C)<br/>1 g/90 mL (90 °C)
| BoilingPt_notes =
| Solubility =1 g/170 mL (25 °C)<br/>1 g/90 mL (90 °C)
| pKa = {{ubl
| 2.42 (amino; H<sub>2</sub>O)
| 4.88 (carboxyl; H<sub>2</sub>O)<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 = ] | isbn = 978-1-4987-5428-6 | pages=5–89 | title-link = CRC Handbook of Chemistry and Physics }}</ref>
}}
}} }}
|Section3= {{Chembox Hazards |Section3={{Chembox Hazards
| MainHazards = eye irritant, some persons may be allergic to this compound
| MainHazards=
| FlashPt= | FlashPt =
| AutoignitionPt =
| Autoignition=
}}
| Section6 = {{Chembox Pharmacology
| Pharmacology_ref =
| ATCCode_prefix =
| ATCCode_suffix =
| ATC_Supplemental =
| ATCvet =
| Licence_EU =
| INN =
| INN_EMA =
| Licence_US =
| Legal_status =
| Legal_AU =
| Legal_AU_comment =
| Legal_CA =
| Legal_CA_comment =
| Legal_NZ =
| Legal_NZ_comment =
| Legal_UK =
| Legal_UK_comment =
| Legal_US =
| Legal_US_comment =
| Legal_EU =
| Legal_EU_comment =
| Legal_UN =
| Legal_UN_comment =
| Pregnancy_category =
| Pregnancy_AU =
| Pregnancy_AU_comment =
| Dependence_liability =
| Addiction_liability =
| AdminRoutes =
| Bioavail =
| ProteinBound =
| Metabolism =
| Metabolites =
| OnsetOfAction =
| HalfLife =
| DurationOfAction =
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}} }}
}} }}

'''4-Aminobenzoic acid''' (also known as ''para''-aminobenzoic acid or '''PABA''' because the two ]s are attached to the ] across from one another in the ''para'' position) is an ] with the ] H<sub>2</sub>NC<sub>6</sub>H<sub>4</sub>CO<sub>2</sub>H. PABA is a white crystalline solid,<ref>{{Cite web |last=PubChem |title=4-Aminobenzoic Acid |url=https://pubchem.ncbi.nlm.nih.gov/compound/4-Aminobenzoic-Acid |access-date=2024-11-19 |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref> although commercial samples can appear gray. It is slightly soluble in water. It consists of a ] substituted with ] and ]s. The compound occurs extensively in the natural world.

==Production and occurrence==
In industry, PABA is prepared mainly by two routes:
* Reduction of ]
* ] of the monoamide derived from ].<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 = ]| 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===
] synthesis pathway]]
PABA is an intermediate in the synthesis of ] 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 ] | access-date=24 January 2014 }}</ref>
Many bacteria, including those found in the human intestinal tract such as ], generate PABA from ] by the combined action of the enzymes ] and ].<ref></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<sub>x</sub>", is no longer recognized as a ]<ref name=MedlinePlus/> because the typical human gut ] generates PABA on its own.

] 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 ]. 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 ], 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 = ]
| 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 ] 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 (]), 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 ]s and ]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>, 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–TiO<sub>2</sub> 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> The chemical structure of PABA, with the amino and carboxyl groups being ''para'' to each other, allows for easy electron delocalization, which reduces the gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). This makes it easier for the electrons in PABA to transition to a higher energy state upon absorbing light.
Patented in 1943, PABA was one of the first active ingredients to be used in ].<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, as shown by a 1975 study ran by Dr. Diane Sekura Snyder and Dr. Marian May.<ref>{{Cite journal |last=Snyder |first=Diane Sekura |last2=May |first2=Marian |date=1975 |title=Ability Of Paba To Protect Mammalian Skin From Ultraviolet Light-Induced Skin Tumors And Actinic Damage |url=http://dx.doi.org/10.1111/1523-1747.ep12610349 |journal=Journal of Investigative Dermatology |volume=65 |issue=6 |pages=543–546 |doi=10.1111/1523-1747.ep12610349 |issn=0022-202X}}</ref>
However, 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. In 2008 it was banned as a sunscreen ingredient in the ] and in 2019 the ] proposed its limited use.<ref>{{Cite web |title=PABA |url=https://www.safecosmetics.org/chemicals/paba/ |access-date=2024-11-19 |website=Safe Cosmetics |language=en-US}}</ref> However, water-insoluble PABA derivatives such as ] 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–TiO<sub>2</sub> Hybrid Nanostructures that result from the method of aqueous in situ synthesis with PABA and TiO<sub>2</sub>.<ref name="Rahal, R. 2008 980–987"/>

==Safety considerations==
PABA is largely nontoxic; the ] of PABA in dogs (oral) is 2 g/kg.<ref name=Ullmann/> Allergic reactions, specifically ] and ],<ref>{{Cite journal |last=Mathias |first=C. G. |last2=Mailbach |first2=H. I. |last3=Epstein |first3=J. |date=1978 |title=Allergic contact photodermatitis to para-aminobenzoic acid |url=https://pubmed.ncbi.nlm.nih.gov/309749/ |journal=Archives of Dermatology |volume=114 |issue=11 |pages=1665–1666 |issn=0003-987X |pmid=309749}}</ref> 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></ref>

==References==
{{reflist}}

{{Other dermatological preparations}}
{{Sunscreening agents}}

{{DEFAULTSORT:Aminobenzoic Acid, 4-}}
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