As preservative

Sodium thiosulfate, O.IA. Weigh 24.818 g of fresh crystals of Na2S203 5H2O, dissolve in distilled water. Add 0.5 g of Na2C03 and 0.5 mL of chloroform as preservative. Dilute to 1 L. 

Contraction in the number of EPA-allowed biocides has heightened efforts to develop naturally derived preservatives and microorganisms capable of countering microbial degradation. Neem oil A. dirachta indica seed extract) has been featured as an exceptional natural candidate for the preservation of cosmetic products. Naturally derived chemicals with antimicrobial properties have been used since antiquity as preservatives. However, displacement of successhil synthetic products by natural products in preservatives of any category remains to be witnessed. 

Pharmaceuticals. A variety of mercury compounds have had pharmaceutical appHcations over the years, eg, mercury-containing diuretics and antiseptics. Whereas some mercury compounds remain available for use as antiseptics such as merbromin [129-16-8] mercuric oxide, and ammoniated mercury [10124-48-8] or as preservatives such as thimerosal [54-64-8] in dmgs and cosmetics, most have been supplanted by more effective substances. A detailed discussion of mercury-containing antiseptics is available (37). Many hospitals use mercury metal to serve as weight for keeping nasogastric tubes in place within the stomach. 

NHydroxyben2oic acid is of significant commercial importance. The most familiar application is the use of several of its esters as preservatives, known as parabens. Also of interest is the use in liquid crystal polymer applications. 

In all fermented foods, microbes contribute as preservatives, ie, by lowering the pH and producing ethanol, or by making the food more palatable. The dehberate use of yeasts as food in themselves is less common. Small beer, the sediment from beer, has been traditionally used as a vitamin supplement for infants. Beginning in 1910, dried, spent brewers yeast was developed as a food, and Candida utilis was used as a food supplement in Germany during World War II. 

The effectiveness of antioxidants as preservatives for fats and oils is evaluated by determining the rate of peroxide development using the Active Oxygen Method (AOM) (29). The development of a rancid odor is used to evaluate the stabiUty of food items (Schaal Oven StabiUty test) (30). 

Sodium and potassium benzoate are substances that may be added direcdy to human food and are affirmed as GRAS (33—35). Benzoic acid and sodium and potassium benzoate are now used as preservatives in such foods as sauces, pickles, cider, fmit juices, wine coolers, symps and concentrates, mincemeat and other acidic pie fillings, margarine, egg powder, fish (as a brine dip component), bottled carbonated beverages, and fmit preserves, jams, and jellies. The popularity of diet soft drinks has led to increased demand for both benzoate salts. 

Salts of neodecanoic acid have been used in the preparation of supported catalysts, such as silver neodecanoate for the preparation of ethylene oxide catalysts (119), and the nickel soap in the preparation of a hydrogenation catalyst (120). Metal neodecanoates, such as magnesium, lead, calcium, and zinc, are used to improve the adherence of plasticized poly(vinyl butyral) sheet to safety glass in car windshields (121). Platinum complexes using neodecanoic acid have been studied for antitumor activity (122). Neodecanoic acid and its esters are used in cosmetics as emoUients, emulsifiers, and solubilizers (77,123,124). Zinc or copper salts of neoacids are used as preservatives for wood (125). 

Ethanol and 2-propanol have also found use ia disinfecting clinical thermometers, and as preservatives to prevent microbial deterioration of cosmetics and mediciaals. They are sometimes combiaed with other disiafectants, namely formaldehyde (69), phenoHcs (70), chlorhexidine (71), hypochlorite (72), and phenols (70). 

Sulfur dioxide, sulfites, and metabisulfites have had extensive use as antimicrobial preservatives in the food industry. In pharmaceuticals they have had a dual role, acting as preservatives and antioxidants. The sulfa dmgs, or sulfonamides, the first effective chemotherapeutic agents to be employed... 

Perfumes, Flavors, Cosmetics, and Soap. Many naturally occurring esters in essential oils and some synthetic esters are important fragrance and flavor compounds (61,62). They are used in perfumes, flavors, cosmetics, soaps, detergents, and air fresheners. Benzyl, butyl, ethyl, methyl, and phenyl esters of benzoic acid are used as flavors, perfumes, and food preservatives. Glyceryl 4-aminobenzoate [136-44-7] and 2-ethyUiexyl 4-dimethylaminobenzoate [21245-02-3] are used in cosmetic sunscreen preparations. Alkyl esters of 4-hydroxybenzoic acid, called parabens, have been used under various names for fungus infections of the skin, and as preservatives in lotions and creams (101). Soap and cosmetic fragrances use large amounts of amyl and benzyl saHcylate. Benzyl saHcylate [118-58-1] is also used in deodorant sprays. 2-Ethylhexyl saHcylate [118-60-5] and 2-ethylhexyl 4-methoxycinnamate [5466-77-3] are used in sunscreen formulations (102). 

Some simple foods can be preservatives in their own right. Honey, salt, sugar, lactic acid, and vinegar are all examples of foods that inhibit microbial action. Some health professionals recommend consuming phytoestrogens from foods such as soybeans to achieve various health benefits. The phytoestrogens in the paraben family, found in blueberries, kill molds and fungi and are often added to food as preservatives. 

Parabens are phytoestrogens found in plants such as blueberries they are used as preservatives in food, cosmetics, sunscreens, shampoos, and many other products. 

Isothiazolinones are a class of broad-spectrum biocides used as preservatives in many household and industrial products. They are used in cosmetics and shampoos as a biocide to kill fungi and bacteria. Unlike the preservatives DMDM hydantoin and imidazolidinyl urea, also commonly used in these products, isothiazolinones do not release formaldehyde, to which some people are sensitive. On the other hand, some people are sensitive to isothiazolinones. 

Sulphur dioxide has extensive use as a preservative in the food and beverage industries. In a pharmaceutical context, sodium sulphite and metabisulphite or bisulphite have a dual role acting as preservatives and antioxidants. 

The aralkyl alcohols and more highly substituted aliphatic alcohols (Fig. 10.2) are used mostly as preservatives. These include ... 

Fig. 10.8 A where the R substituents are alkyl or heterocyclic radicals to give compounds such as cetyltrimethylammonium bromide (cetrimide), cetylpyridinium chloride and benzalkonium chloride. Inspection of the stmctures of these compounds (Fig. 10.8B) indicates the requirement for good antimicrobial activily of having a chain length in the range Cg to Cig in at least one of the R substituents. In the pyridinium compounds (Fig. 10.8C) three of the four covalent links may be satisfied by the nitrogen in a pyridine ring. Polymeric quaternary ammonium salts such as polyquatemium 1 are finding increasing use as preservatives.

Preservatives may inelude disinfeetant and antiseptic chemicals together with eertain compounds used almost exclusively as preservatives. They are added to mar industrial, including pharmaceutical, products which may, by their nature, support the growth of bacteria and moulds causing spoilage of the product and possibly infection of the user. In the field of pharmaceutical preservation, addition of an inhibitory substance to a multidose injection (Chapter 21) or the prevention of growth in aqueous suspensions ofdmgs intended for oral administration (Chapter 18) are prime examples. 

Sulphur dioxide, sulphites and bisulphites, used as preservatives in fruit juices, ciders and penys are yet other examples. 

Composition of Emulsion, The prototype oil/water emulsion described in Table I contained ingredients typical of a large number of cosmetic products, although simplified somewhat to avoid analytical problems. The aqueous phase contained sodium lauryl sulfate (SLS) as emulsifier, 0,2% (19 n ) DEA as precursor to NDEIA and 0,1% benzoic acid as preservative. 

---