Isobutylparaben  is a chemical compound belonging to the paraben chemical family, the isobutyl ester of p-hydroxybenzoic acid.

It occurs in the form of a white powder.

What it is used for and where

It is a preservative used in food, pharmaceuticals, cosmetics and more.

It is used as a preservative against:

• fungi
• yeasts
• molds

Since 2014, isopropylparaben, isobutylparaben, benzylparaben, phenylparaben, and pentylparaben have been banned in cosmetics by European legislation (1).

Parabens

Parabens are chemical preservative compounds that have been the subject of attention in the scientific literature as possible endocrine disruptors (particularly propylparaben and butylparaben), i.e. with the possibility of damaging the hormone-producing glands in our bodies, particularly in the breasts. The 2004 study by Darbre et al. showed that parabens remain in our bodies as intact esters (2). Following this study, some of the scientific literature in 2005 and 2006 cast doubt on Darbre's conclusions and claimed they were limited. However, both the US FDA and the European SCCP authorised in 2006 the use of a single paraben in cosmetic products at a concentration of 0.4% and the use of total parabens at a concentration of 0.8% (3). However, there is no shortage of studies that consider the restrictions unnecessary: M. G. Kirchhof et al. in 2013 found that parabens are among the safest and most well-tolerated preservatives and that current data do not support drastic regulations or personal exposure restrictions (4). Darbre in 2014 published a further study in which he showed how parabens can cause DNA damage (5).

Isobutylparaben studies

Typical optimal commercial product characteristics Isobutylparaben

Appearance	White fine powder
Boiling Point	302.3±15.0 °C at 760 mmHg
Melting Point	76°C
Flash Point	125.4±13.2 °C
Density	1.1±0.1 g/cm3
Vapour Pressure	0.0±0.7 mmHg at 25°C
Index of Refraction	1.524
Heavy metals	≤10 ppm
Loss on drying	≤2.0%
Water	≤1.0%
Residue on ignition	≤0.1%
Sulphated ash	≤0.05%/g
PSA	46.53000
LogP	3.28
Storage	0-6°C
Safety

• Molecular Formula   C₁₁H₁₄O₃
• Molecular Weight   194.23 g/mol
• Exact mass   194.094299
• UNII: 0QQJ25X58G
• CAS: 4247-02-3
• DSSTox Substance ID  DTXSID4020749
• IUPAC  2-methylpropyl 4-hydroxybenzoate
• InChI=1S/C11H14O3/c1-8(2)7-14-11(13)9-3-5-10(12)6-4-9/h3-6,8,12H,7H2,1-2H3 
• InChl Key      XPJVKCRENWUEJH-UHFFFAOYSA-N
• SMILES     CC(C)COC(=O)C1=CC=C(C=C1)O
• EC Number: 224-208-8
• PubChem Substance ID 329762940
• MDL number MFCD00020167
• ChEBI   178256

Synonyms: 

• Isobutyl 4-hydroxybenzoate
• Isobutylparaben
• Isobutyl p-hydroxybenzoate
• 2-Methylpropyl 4-hydroxybenzoate
• isobutyl paraben
• Isobutyl-4-hydroxybenzoate
• Isobutyl parahydroxybenzoate
• 4-Hydroxybenzoic Acid Isobutyl Ester
• Benzoic acid, 4-hydroxy-, 2-methylpropyl ester
• p-Oxybenzoesaureisobutylester
• p-Hydroxybenzoic acid isobutyl ester
• 4-Hydroxybenzoic acid, 2-methylpropyl ester
• Isobutyl4-hydroxybenzoate
• SCHEMBL34633
• Methylpropyl p-hydroxybenzoate

References_______________________________________________

(1) COMMISSION REGULATION (EU) No 358/2014 of 9 April 2014 Amending Annexes II and V to Regulation (EC) No 1223/2009 of the European Parliament and of the Council on Cosmetic Products; Annex II the Following Entries 1374 to 1378. [(accessed on 17 January 2021)]; Available online: https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:32014R0358&from=EN#d1e32-7-1. 

(2) Darbre PD, Aljarrah A, Miller WR, Coldham NG, Sauer MJ, Pope GS. Concentrations of parabens in human breast tumours. J Appl Toxicol. 2004 Jan-Feb;24(1):5-13. doi: 10.1002/jat.958.

(3) https://www.fda.gov/cosmetics/cosmetic-ingredients/parabens-cosmetics

Cosmetic Ingredient Review Expert Panel. Final amended report on the safety assessment of Methylparaben, Ethylparaben, Propylparaben, Isopropylparaben, Butylparaben, Isobutylparaben, and Benzylparaben as used in cosmetic products. Int J Toxicol. 2008;27(Suppl 4):1-82.

(4) Kirchhof MG, de Gannes GC. The health controversies of parabens. Skin Therapy Lett. 2013 Feb;18(2):5-7.

(5) Darbre PD, Harvey PW. Parabens can enable hallmarks and characteristics of cancer in human breast epithelial cells: a review of the literature with reference to new exposure data and regulatory status. J Appl Toxicol. 2014 Sep;34(9):925-38. doi: 10.1002/jat.3027.

Some of the best studies on parabens:

Paraben Concentrations in Maternal Urine and Breast Milk and Its Association with Personal Care Product Use.
Fisher M, MacPherson S, Braun JM, Hauser R, Walker M, Feeley M, Mallick R, Bérubé R, Arbuckle TE.
Environ Sci Technol. 2017 Apr 4;51(7):4009-4017. doi: 10.1021/acs.est.6b04302.

Metabolism and elimination of methyl, iso- and n-butyl paraben in human urine after single oral dosage.
Moos RK, Angerer J, Dierkes G, Brüning T, Koch HM.
Arch Toxicol. 2016 Nov;90(11):2699-2709. Epub 2015 Nov 25.

Reduction in semen quality after mixed exposure to bisphenol A and isobutylparaben in utero and during lactation periods.
Yang YJ, Hong YP, Chae SA.
Hum Exp Toxicol. 2016 Aug;35(8):902-11. doi: 10.1177/0960327115608927.

Toxicological evaluation of isopropylparaben and isobutylparaben mixture in Sprague-Dawley rats following 28 days of dermal exposure.
Kim MJ, Kwack SJ, Lim SK, Kim YJ, Roh TH, Choi SM, Kim HS, Lee BM.
Regul Toxicol Pharmacol. 2015 Nov;73(2):544-51. doi: 10.1016/j.yrtph.2015.08.005.

Final amended report on the safety assessment of Methylparaben, Ethylparaben, Propylparaben, Isopropylparaben, Butylparaben, Isobutylparaben, and Benzylparaben as used in cosmetic products.
Int J Toxicol. 2008;27 Suppl 4:1-82. doi: 10.1080/10915810802548359.