Beta hydroxy acids

Salicylic acid is a beta hydroxy acid. Glycolic acid is an alpha hydroxy acid, as are lactic acid, citric acid, and many others. Hydroxy acids are compounds that are both alcohols and acids at the same time. Hydroxy acids are used as chemical peeling agents. Alpha hydroxy acids can make the skin more sensitive to ultraviolet light by removing the skin s protective outer layers. Some alpha hydroxy acids ... 

Each component of Jessner s solution has specific effects (Fig. 3.1). Salicylic acid (ortho hydroxy benzoic acid) is a beta hydroxy acid agent... 

Salicylic acid (ortho hydroxybenzoic add) is a beta hydroxy acid agent. It is a lipophilic compound which produces desquamation of the stratum corneum via removal of intercellular lipids [3] (see salicylic acid section). Given its keratolytic effects, it has become an increasingly popular superficial peeling agent. Salicylic acid peels induce injury via thinning or removal of the stratum corneum. In addition, salicylic acid potentially enhances the penetration of TCA. 

Vitamin C formulations Alpha hydroxy acids Polyhydroxy acids Beta hydroxy acids... 

Alpha hydroxy acids (AHAs) are water-soluble substances and thereby penetrate the outermost epidermal skin layers. In contrast, beta hydroxy acids (BHAs) are lipid (fat) soluble and are capable of penetrating to the underlying layers of skin (the dermis) located 1-5 mm below the surface of the skinJ2 Most AHAs are derived from plant materials and marine sources. Commonly used AHAs include malic acid (found in apples), ascorbic acid (a common ingredient in numerous fruits), glycolic acid (a constituent of sugar cane), lactic acid (a component of milk), citric acid (naturally abundant in citrus fruits), and tartatic acid (found in red wine). A common BHA is salicylic acid (an ingredient in aspirin). 

Figure 13.10.2 The structure of a beta hydroxy acid, a substituted carboxylic acid in which the hydroxyl substituent is attached to the beta position, i.e., at a carbon atom two positions away from the carboxylic acid functionality.

KEY TERMS carboxylic acid carboxyl functionality beta hydroxy acid alpha hydroxy acid... 

F. F. Huerta and J. E. Backvall, Enantio-selective synthesis of beta-hydroxy acid derivatives via a one-pot aldol reaction -dynamic kinetic resolution, Org. Lett. 2001, 3(8), 1209-1212. 

Glycerol is a widely used humectant and moisturizer in cosmetics, and considerable research has been done on its effect on the stratum corneum functionality (75). Glycerol was identified as an effective agent in the formation of lipid crystals under conditions of low humidity. The use of alpha- and beta-hydroxy acids on skin desquamation is now well established and widely practiced (76). New lipophilic variants of salicylic acid are reported to affect comeodesmolysis by acting on the whole stmcture of the comeodesmosomes. Alpha-hydroxy acids fractionate the cor-neodesmosomes only (77). 

The first one that was recognized as being effective was retinoic acid. This was a prescription ointment drug until the over-the-counter product was approved in the mid-nineties, and proved efFective. Another is glycolic acid, which is available in makeup products or in more concentrated forms from physicians. There is also Kojic acid, alpha hydroxy acid, beta hydroxy acid, and the newest vitamin C products. Hydroquinone is another chemical that is used because it has a bleaching effect on the skin. 

Different agents have been studied and depicted effectual in achieving a superficial depth peel. Among these, preferred for use are alpha-hydroxy adds (AHAs), beta-hydroxy acid (BHA), Jessner s original and modified solutions, and trichloroacetic acid (TCA). 

Salicylic acid is a lipophilic beta-hydroxy acid which is used as a peeling agent, compounded as 20-40% solution with ethanol. It is a hydroxyl derivative of benzoic acid and represents a carboxylic add attached to an aromatic alcohol, phenol. It is a white crystalline powder derived from willow bark, winter green leaves, and sweet birch [15]. 

A large number of combination peels are in the market which combine various alpha-hydroxy acids and also with beta-hydroxy acids. There are other proprietary peels, the exact composition of which is not known. There are hardly any randomized controlled studies on these in Asian patients. There are concerns about their stability and efficacy. Some are made for home use. A comparative study on 44 Indian patients with acne which had two groups, one receiving 35% glycolic acid peels and the other 20% salicylic acid-10% mandelic acid peels for six sessions at 2-weekly intervals, found salicylic-mandelic peel more efficacious for active acne and postacne hyperpigmentation [24]. Mandelic acid penetrates less but in the combination with salicylic acid has a beneficial role in postinflammatory hyperpigmentation. 

Zhang, N., Yang, A., Rogers, ID., Zhao, IJ. (2004) Quantitative analysis of simvastatin and its beta-hydroxy acid in human piasma using automated liquid-liquid extraction based on 96-well plate format and liquid chromatography-tandem mass spectrometry. J. Pharm. Biomed. Anal, 34,175-187. 

Wu Y, Zhao J, Hettion JD, Korfmacher WA, Lpaiguera AP, Lin C-C. Microsample determination of lovastatin and its hydroxy acid metabolite in mouse and rat plasma by liquid ehromatography-ionspray tandem mass spectrometry. J Mass Spectrom. 1997 32 379-87. Zhao JJ, Xie IH, Yang AY, Roadcap BA, Rogers JD. Quantitation of simvastatin and its beta-hydroxy acid in human plasma by liquid-liquid cartridge extraction and liquid chromatography-tandem mass spectrometry. J Mass Spectrom. 2000 35 1133-43. 

Watanabe S, Suga K, Eujita T, Fujiyoshi K. The direct synthesis of beta-hydroxy-acids by lithium naphthalene and acetic acid. Isr J Chem 1970 8 731-736. 

Beta hydroxy acid peels with pK around 3... 

It is becoming common for beta hydroxy acid (BHA) peels to be used instead of the stronger alpha hydroxy acid (AHA) peels due to BHA s ability to get deeper into the pore than AHA. Studies show that BHA peels control oil, acne as well as remove dead skin cells to a certain extent better than AHAs due to AHAs only working on the surface of the skin. 

Salicylic acid (from the Latin Sahx meaning willow tree) is a biosynthesized, organic, beta hydroxy acid that is often used. Sodium salicylate is converted by treating sodium phenolate (the sodium salt of phenol) with carbon dioxide at high pressure and temperature. Acidification of the product with sulfuric acid gives salicylic acid. Alternatively, it can be prepared by the hydrolysis of Aspirin (acetylsahcyhc acid) or Oil of Wintergreen (methyl salicylate) with a strong acid or base. 

Also known as 2-hydroxybenzoic acid, it is a crystalline carboxylic add and classified as a beta-hydroxy acid. Salicylic acid is slightly soluble in water but very soluble in ethanol and ether (like phenol and resorcinol). It is made from sodium phenolate and this explains its direct relationship with phenol with which it shares certain toxic jjroperties that become apparent when used in great quantity and on large surface areas. 

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