Alpha hydroxyl acid

The alpha carbon atom is that adjacent to the COOH group (as with alpha-hydroxyl acids - cf Chapter 6). 

Aluminium chlorohydrate is a widely used active ingredient for antiperspirant compositions. This salt requires a hydrophilic solvent at low pH values to remain stable. Structured microemulsions can be used to formulate clear and viscous products with this active. These products can be used in solid applicators such as firm stick applicators [35]. The o/w microemulsions can be based on fatty alcoholethoxylates with an organic or silicon oil phase [36]. An improved temperature stability in the range of 0-70°C for such formulations can be achieved by a combination of oxyalkylene-modified siloxanes, pentacyclosiloxane and glycol [37]. The addition of alpha-hydroxylic acids results in an improved skin feel with decreased tackiness [38]. 

Ma PX, Zhang R, Xiao G, Franceschi R (2001) Engineering new bone tissue in vitro on highly porous poly (alpha-hydroxyl acids)/hydroxylapatite composite scaffolds. J Biomed Mater Res 54 284-293 Macdonald A, Moore BK, Newton CW, Brown CE (1994) Evalrration of an apatite cement as a root end filling material. J Endodontics 20 598-604... 

Therefore it is recommended that beginners start by using low concentrations of the nonaromatic diprotic or tripotic alpha hydroxyl acids with pK > 3. 

Step II is the daily skin care program using cleansing granules, alpha hydroxyl acid toners and vitamin A conditioning lotions to accelerate the jjroduction of new skin cells. These three skin care formulations are used daily. However, patients with dry skin or who live in a dry climate start slowly, skijjping days as needed to avoid retinoid dermatitis. 

These hot spots are less troublesome as the concentration is decreased. In our experience, we have gone from 45%, to 35%, to 25%, to 15%, and, now, to 7.5% TCA. We discovered during these dilutions that the results with TCA are coat dependent. Whereas, the results with alpha hydroxyl acids are time-dependent, and phenol results are cardio-dependent, TCA results are dependent on the number of layers applied. The more coats that are used the deeper the peel, so multiple coats of a 15% TCA can mimic the results of one or two coats of 30% TCA. These dilute peels take more time and more coats - which is exactly what we want - so we have more time to watch the blanch develop and we can discontinue applications at a predictable foggy-red blanch. The weaker strengths of TCA give us more time to think. 

CYP8A1 is the complementary enzyme to CYP5 in that it synthesizes prostacyclin in the arachidonic acid cascade. CYP8B1 catalyzes the steroid 12-alpha hydroxylation in the cholic acid biosynthesis. 

An alpha hydroxy acid is an organic carboxylic acid in which an additional hydroxyl functional group (-OH) is present at the alpha position, i.e., on the carbon adjacent to the carboxyl functionality, -COOH. Figure 13.10.1 presents the struc-... 

Ali MA, Konishi T (1997) Enhancement of hydroxyl radical generation in the Fenton reaction by alpha-hydroxy acid. Biochem Mol Biol Int 46 137-145 An bar M, Pecht I (1964) The sonolytic decomposition of organic solutes in dilute aqueous solutions. 

Upha- Ry roxy Acid Anhydrides.—When an alpha-hydroxy acid is heated, or when it simply stands over sulphuric acid, two molecules react together as an alcohol-acid compound, in the manner described above in (3) and (4). The alcoholic hydroxyl of one molecule reacts with the acid hydroxyl of the other molecule and water is lost with the formation of a single anhydride which is really an ester. This compound then loses a second molecule of water by the reaction between the remaining alcoholic and acid hydroxyl groups forming a double anhydride or a double ester as discussed above in (6). The name of such double anhydride takes the termination ide in place of ic of the original 16... 

At least 2 wt% alpha-hydroxylated carboxylic acids and theirs derivatives... 

Water is added across the double bond in the next step, catalyzed by fumarase, to give malic acid, or malate. Finally, malate dehydrogenase removes the two hydrogens from the hydroxyl carbon to regenerate the alpha-keto acid, oxaloacetate ... 

Matsunaga I, Sumimoto T, Ueda A, Kusunose E, Ichihara K (2000) Fatty acid-specific, regiospecific, and stereospecific hydroxylation by cytochrome P450 (CYP152B1) fiom Sphingomonas paucimobi-lis substrate structure required for alpha-hydroxyl-ation. Lipids 35 365 371... 

Landwehr M, Hochrein L, Otey CR, Kasrayan A, Backvall JE, Arnold FH (2006) Enantioselective alpha-hydroxylation of 2-arylacetic acid derivatives and buspirone catalyzed by engineered cytochrome P450 BM3. J Am Chem Soc 128 6058-6059... 

Fig. 3. Deoxycholic acid. Refer to legend of Fig. 1 for further explanation. The 3 and 12 refer to alpha hydroxyl groups at positions 3 and 12.

---