Structure of Methylparaben
Methylparaben, more scientifically known as methyl parahydroxybenzoate or methyl 4-hydroxybenzoate, is a colorless and nearly tasteless crystalline powder, with a molecular weight of 152.2. It is used primarily as an antifungal agent in foods, cosmetics, sunscreens, shampoos and medicines. Methylparaben has been found to be nearly non-toxic, or "generally recognized as safe" (GRAS), with only rare cases of sensitivity reported. It readily absorbs gastrointestinally and through the skin.
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Drosophila
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Methylparaben is important in the breeding of drosophila, which is more generally known as the fruit fly. The fruit fly is important to genetic research, due to its extremely rapid life cycle and its genetic complexity. It is studied to assist in the understanding of other life forms, including humans. The food cultures for raising them in the laboratory may include a small quantity of methylparaben as a mold inhibitor as mold destroys developing flies.
Synthesis
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Although it is found in nature, methylparaben is commercially synthesized by a modification of the Kolbe-Schmitt reaction, in which carbon dioxide is reacted with potassium phenoxide:
1) 2 KOH + CO₂ + HO-C₆H... ' KO-C₆H₄-COO־ K⁺ + 2 H₂O
2) KO-C₆H₄-COO־ K⁺ + H₂SO₄ ' HO-C₆H₄-COOH + K₂SO₄
3) CH₃OH + HO-C₆H₄-COOH + H₂SO₄ + ∆ ' HO-C₆H₄-COOCH₃ + H₂OIf sodium hydroxide is used in the reaction instead of potassium hydroxide (a large atom), the reaction will not create the para compound (1,4 reaction sites on the benzene ring), but the ortho compound (1,2)
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Safety Concerns
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Although it has been generally conceded that methylparaben is essentially non-toxic, not all agree. References are cited indicating metabolites of methylparaben build up in the human body, particularly in women's breasts and ovaries.
The Food and Drug Administration restricts methylparaben use in food products to "good manufacturing processes" which amounts to less than 0.1 percent.
Amended Evaluation by NIH
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In 2008, the U.S. National Library of Medicine, in conjunction with the National Institutes of Health, posted a final amended report on the safety assessment of methyl-, ethyl-, propyl-, isopropyl-, butyl-, isobutyl- and benzyl- parabens as used in cosmetic products in their Internet Journal of Toxicology. Although they report, in certain instances, that some undesirable results occurred, those undesirable results were many times less severe (sometimes hundreds of thousands of times less) than those found in the estrogen hormone, estradiol.
Biodegradability
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For those desirous of keeping the environment clean of substances that can not be biodegraded, the question of the biodegradability of the parabens is very important. It appears that standard parabens all break down completely in the environment to other substances, natural occurring, which themselves break down further into harmless products.
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References
- Photo Credit Methylparaben: Rohieb/Commons.wikimedia.org
