Palmitate esters

Qindamycin, 7(5)-7-chloro-7-deoxyliQcomycin [18323-44-9] (1, R = H, R = Q), also known as Cleocin, first resulted from the reaction of lincomycin and thionyl chloride (54) improved synthetic methods involve the reaction of lincomycin and triphenylphosphine dichloride or triphenylphosphine in carbon tetrachloride (55). Clindamycin is significantly more active than lincomycin against gram-positive bacteria in vitro, and is absorbed rapidly following oral adnainistration. Clindamycin 2-palmitate [36688-78-5], (6, R = R = OC(CH2) 4CH2), 2-palmitate ester of clindamycin, is... 

In recent years, many parent dmgs have been converted to esters to generate so-called prodmgs ia order to overcome some undesirable property such as bitter taste, poor absorption, poor solubiUty, and irritation at site of iajection. For example, antibiotics such as chloramphenicol [56-75-7] and clindamycin [18323-44-9] have been derivatized as their palmitate esters ia order to minimise their bitter taste. 

Their hydrophobicity and their plasticity were appreciated and used for a long time in a wide range of activities. To our knowledge, the first wax to have been exploited is beeswax. Beeswax is produced by various species of bees in the world, and it has a melting point between 62°C and 64°C. It mainly contains homologous series of even-numbered fatty acids (C22 C34, C2 being the predominat compound), odd-numbered ra-alkanes (C2i C33, C27 being the major compound) and even-numbered palmitic esters from C40 to C52 (Tulloch and Hoffman, 1972 Kolattukudy, 1976). Hydroxy esters, diesters and hydroxy diesters also form part of beeswax to a lesser extent. 

Beeswax Produced by bees Even numbered fatty acids (C22 C34) Odd numbered n alkanes (C2i C33) Even numbered palmitic esters (C40 C52)... 

Odd numbered carbon alkanes, abundant palmitic acid, tetracosenoic (lignoceric) acid, palmitate esters, long chain alcohols Beeswax [11,23,27]... 

Absorption - Chloramphenicol base is absorbed rapidly from the intestinal tract and is 75% to 90% bioavailable. The inactive prodrug, chloramphenicol palmitate, is rapidly hydrolyzed to active chloramphenicol base. Bioavailability is approximately 80% for the palmitate ester. The bioavailability of the IV... 

Vitamin A, vitamin E and their acetate and palmitate esters were determined in tablets. The tablet powder was mixed with sand and loaded into the extraction vessel CO2 alone was used for extraction at 40°C for 15 min. The CO2 was vented to... 

Beeswax is the most important of the insect waxes. As mentioned above it comes from the honeycomb found in beehives and consists primarily of the palmitic ester of myricyl alcohol (see Table 1 for complete chemical analysis). Beeswax resembles the microcrystalline/paraffin waxes derived from petroleum. It is noted for its plasticity, ductility and its ability to form stable emulsions... 

FIGURE 19.4 Peak serum levels of chloramphenicol as a function of the percent of polymorph B (palmitate ester) in mixtures with polymorph A. (Redrawn from Aguiar, A.J., Krc, J., Kinkel, A.W., and Samyn, J.C. (1967). J. Pharm. Sci., 56 847-853. With permission from American Pharmaceutical Association.)... 

Vitamin A or a precursor must be provided in the diet. This vitamin occurs in various forms (vitamers) retinol (alcohol), retinal (aldehyde), retinoic acid and vitamin A palmitate (ester). Requirements for vitamin A are usually expressed in international units (IU) per kg of diet. The international standards for... 

Vitamin A (IFN 7-05-142), as the acetate ester, palmitate ester, propionate ester or a mixture of these esters. 

Onset of action of palmitic ester formulation A/ithin 2-3 days... 

Mitra, A. K., Ghosh, L. K. and Gupta, B. K. (1993). Development of methods for the preparation and evaluation of chloramphenicol palmitate ester and its biophar-maceutically effective metastable polymorph. Drag Dev. Ind. Pharm., 19, 971-80. [246]... 

About 95% of vitamin A is stored as its palmitate ester in the liver. It is released in plasma as and when required. 

E472b Glycerol-lacto-palmitic esters of monoglycerides LACTEM GLP Oil, polyhydric alcohol and organic acid... 

Chemistry. The commercial form cf vitamin A is all-trans retinol, usually formulated as the acetate or palmitate ester. The active forms are the two oxidation products (Fig. 8.1, (l)retinal, which is a structural component of the visual pigment rhodopsin, and (2)retinoic acid, which is required for cell differentiation. There are specific nuclear receptors for retinoic acid. Although the vitamin is marketed in the all-trans form, retinal and retinoic acid are present, in vivo in cis forms. There are also commercial forms related to the retinoic acid structure that have cis stereochemistry. 

Dosage Foims. Retinolisunstable.lt easily dehydrates (Fig. 8.6), forming a stable carbonium ion. Therefore, the two most common forms for both oral and parenteral administration are the acetate or palmitate esters. With the extensive conjugation retinol is light sensitive and subject to oxidation. Therefore, the vitamin formulator must protect the product from light and air. 

Chloramphenicol prepared as its palmitate ester is an interesting study example with respect to polymorphism. This ester, synthesized to avoid the bitterness of the active moiety (see below), exists as four polymorphs, three crystalline forms and an amorphous one. Polymorphs A and B have been found in commercial preparations but only form B leads to satisfactory blood levels. This effect was first attributed to the lower solubility of the "inactive" form A (26), but it was later proved that the higher susceptibility of form B to esterases was, in fact, involved (27). 

Palmitic ester, C40Ht3N O4S2, pipotiazine palmitate, RP 19552, PipoHii L4. 

Beeswax is obtained from the honey-comb of bees it consists chiefly of the palmitic ester of myricyl alcohol, C15H31COOC30H61. Some cerotic acid, C26H53COOH, is also present in the wax. It finds many uses in the arts. 

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