Acid mantle

Here the TEWL-value measurements showed that Kujalnik peloids and magnesium pelobischofite complex salutary potentize each other in their mixtures and provide the effective preservation of acidic mantle of the skin. Besides, the pelobischofite addition to the cosmetic cream compositions results in the effective coverlet moistening. Also, the pelobischofite addition provides the decrease of the negative surfactants effect on the skin health. The TWL parameter value is less by half, the water balance of the skin is normalized and the wrinkled skin becomes smoothed out and velvety. 

Beyond physical barrier protection, several natural processes lead to skin surface conditions unfavorable to microbial growth. Both sebaceous and eccrine secretions are acidic, lowering the surface pH of the skin below that welcomed by most pathogens. This acid mantle (pH 5) [16] is moderately bacteriostatic. Sebum also contains a number of short-chain fungistatic and bacteriostatic fatty acids, including propanoic, butanoic, hexanoic, and heptanoic acids [17]. That the skin s surface is dry also offers a level of protection. It comes as no surprise that fungal infections and other skin infections are more prevalent in the skin s folds... 

The pH of intact skin ranges from about 4.8 to 6.0, while interstitial fluid exhibits a pH that is near neutral. The low pH on skin is attributed mainly to the presence of the so-called acid mantle , a natural skin barrier to the external environment [172], Wagner et al. [173] measured both in-vivo and in-vitro pH profiles across human stratum comeum (SC) using the tape stripping technique and a flat surface pH electrode (InLab 426 from Mettler Toledo). They found a steep pH increase from pH 6 to 8 in the first 100 pm after the removal of the SC. 

The pH-value of the skin surface has been investigated by many researchers since the end of nineteenth century. The acidic nature of the skin surface was first mentioned by Heuss in 1892.1 In 1928, Schade and Marchionini2 used the term acid mantle of the skin (sauremantel) for the first time. Since this, that phenomenon has become of great interest, and many studies trying to explain its function and the mechanism of formation have been carried out. Nevertheless, many questions remain unexplained. 

Ohman, H. and Vahlquist, A. The pH gradient in the stratum corneum differs in X-linked recessive and autosomal dominant ichthyosis a clue to the molecular origin of the acid mantle J. Invest. Dermatol., Ill, 674, 1998. 

The acidic environment of the ear skin surface (around pH 6), sometimes referred to as the acid mantle of the ear, is thought to he a defence against invading microorganisms. 

Another problem with basic skin products is related to an acid mantle that bathes the top layer of the skin, the epidermis. This fluid—composed of oil, sweat, and other ceU secretions—is a natural defense against bacterial infections. Strongly basic soaps can neutralize the protective acid mantle. People with acne or oily skin must be careful not to remove the acid mantle. 

The skin has two layers, the outer layer is called the epidermis and the inner the dermis. The epidermis has a protective function. It consists of densely packed flat cells, thicker in some areas, like the palms of the hands, which are more subject to injury. It is covered by a moist film known as an acid mantle, made up of secretions from sweat and sebaceous glands, that helps to protect from acids, alkalis, excessive water, heat and friction by preventing the skin from drying out. The natural grease of the skin can be removed by solvents. In the deeper layer of the epidermis are pigment cells which produce the tan following exposure to sunlight and protect the body from ultraviolet radiation. 

Polyglycols are insensitive to electrolytes. They are by nature completely neutral, can be adjusted to any dermatologically acceptable pH, and can be adapted to the pH of the acid mantle of the skin. 

A setup similar to the preceding one is used in this experiment except that provision should be made for heating the reaction vessel (steam bath, oil bath, or mantle). Lithium aluminum hydride (10 g, 0.26 mole) is dissolved in 200 ml of dry -butyl ether and heated with stirring to 100°. A solution of 9.1 g (0.05 mole) of ra j-9-decalin-carboxylic acid (Chapter 16, Section I) in 100 ml of dry -butyl ether is added dropwise over about 30 minutes. The stirring and heating are continued for 4 days, after which the mixture is cooled and water is slowly added to decompose excess hydride. Dilute hydrochloric acid is added to dissolve the salts, and the ether layer is separated, washed with bicarbonate solution then water, and dried. The solvent is removed by distillation, and the residue is recrystallized from aqueous ethanol, mp 77-78°, yield 80-95 %. 

The carbonyl compound to be reduced (0.1 mole) is placed in a 250-ml round-bottom flask with 13.5 g of potassium hydroxide, 10 ml of 85% hydrazine hydrate, and 1(X) ml of diethylene glycol. A reflux condenser is attached and the mixture is heated to reflux for I hour (mantle). After refluxing 1 hour, the condenser is removed and a thermometer is immersed in the reaction mixture while slow boiling is continued to remove water. When the pot temperature has reached 200°, the condenser is replaced and refluxing is continued for an additional 3 hours. The mixture is then cooled, acidified with concentrated hydrochloric acid, and extracted with benzene. The benzene solution is dried, and the benzene is evaporated to afford the crude product, which is purified by recrystallization or distillation. 

A solution of 3 g of the nitrile, water (5 moles per mole of nitrile), and 20 g of boron trifluoride-acetic acid complex is heated (mantle or oil bath) at 115-120° for 10 minutes. The solution is cooled in an ice bath with stirring and is carefully made alkaline by the slow addition of 6 A sodium hydroxide (about 100 ml). The mixture is then extracted three times with 100-ml portions of 1 1 ether-ethyl acetate, the extracts are dried over anhydrous sodium sulfate, and the solvent is evaporated on a rotary evaporator to yield the desired amide. The product may be recrystallized from water or aqueous methanol. Examples are given in Table 7.1. 

A mixture of cyclohexanone (11.8 g, 0.12 mole), ethylene glycol (8.2 g, 0.13 mole), /j-toluenesulfonic acid monohydrate (0.05 g), and 50 ml of benzene is placed in a 250-ml round-bottom flask fitted with a water separator and a condenser (drying tube). The flask is refluxed (mantle) until the theoretical amount of water (approx. 2.2 ml) has collected in the separator trap. The cooled reaction mixture is washed with 20 ml of 10 % sodium hydroxide solution followed by five 10-ml washes with water, dried over anhydrous potassium carbonate, and filtered. The benzene is removed (rotary evaporator) and the residue is distilled, affording l,4-dioxaspiro[4.5]decane, bp 65-67713 mm, 1.4565-1.4575, in about 80% yield. 

A 250-ml round-bottom flask is charged with a mixture of cyclohexanone (14.7 g, 0.15 mole), morpholine (15.7 g, 0.18 mole), and / -toluenesulfonic acid monohydrate (0.15 g) in 50 ml of toluene. The flask is fitted with a water separator and a condenser and is brought to reflux (mantle). The separation of water begins immediately and the theoretical amount (2.7 ml) is obtained in about 1 hour. Without further treatment, the reaction mixture may then be distilled. After removal of the toluene at atmospheric pressure, the product is obtained by distillation at reduced pressure, bp II8-I207IO mm, 1.5122-1.5129, in about 75% yield. 

The carboxylation of ketones is carried out essentially as in the preceding experiment, but at slightly higher temperatures (requiring an oil bath or mantle). Thus, acetophenone (6 g, 0.05 mole) in 100 ml of approx. 2 M MMC is stirred and heated at 110-120° for 1 hour. After cooling, hydrolysis in the acid-ice mixture, and isolation from ether, benzoylacetic acid, mp 99-100°, is obtained in 68% yield. Similarly, 1-indanone gives l-indanone-2-carboxylic acid, mp 100-101°, in 91 % yield. 

In a 500-ml round-bottom flask fitted with a condenser, and a heating mantle is placed a mixture of 25 g of diethyl 5-(l -carboxy-2 -oxocyclohexyl)valerate, 70 g of barium hydroxide, and 200 ml of methanol, and the mixture is refluxed for 24 hours. After cooling, the mixture is acidified (pH 4) by cautious addition of cold 10% aqueous hydrochloric acid. The acidified solution is saturated with sodium chloride and then extracted three times with 100-ml portions of chloroform. The combined chloroform extracts are dried (anhydrous magnesium sulfate) and evaporated. On vacuum distillation, the residue affords the product (about 15 g), bp 176-17870.5 mm. 

The ketoester is mixed in a suitable round-bottom flask with excess 6 N sulfuric acid. The flask is fitted with a condenser and a mantle, and the mixture is refluxed gently for 3-4 days. The cooled reaction mixture is extracted with ether, the ether is washed with bicarbonate solution and water, then dried, and the solvent is evaporated. On distillation, the residue affords 2-methylcyclooctanone, bp 97-98718 mm, 86712 mm, 1 4656,... 

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