Para-Aminobenzoate

The filtrates are combined, cooled, and extracted with three successive 200 cc portions of ether. The pH of the filtrate is then raised to 3.5 with sodium hydroxide and the filtrate extracted with six successive 200 cc portions of ether to yield the balance of the product. The crude para-aminobenzoic acid product is recovered by evaporation of ether and is suspended in hot benzene, cooled and filtered to remove benzoic and toluic acids together with small amounts of impurities soluble in the filtrate. Recrystallization of the product from 200 cc of water yields 14.5 grams of light tan needles of para-aminobenzoic acid having an acid number of 411 (theoretical value 409). 

The following molecular model is a representation of para-aminobenzoic acid (PABA), the active ingredient in many sunscreens. Indicate the positions of the multiple bonds, and draw a skeletal structure (gray = C, red = O, blue = N, ivory - H). 

Para-aminobenzoic acid (PABA), HCjH NO is used in some sunscreen agents. A solution is made by dissolving 0.263 mol of PABA in enough water to make 750.0 mL of solution. The solution has [H+] = 2.6 X 10-3 M. What is Ka for PABA ... 

Para-aminobenzoic add is an essential vitamin for many bacteria ... 

Sun worshipers and those who work outside can protect themselves from ultraviolet exposure with skin creams that contain UV-absorbing molecules. The UV-absorbing molecule in the first sunscreens was PABA, para-aminobenzoic acid. However, this compound may have toxic effects of its own. The UV-absorbing components of current sunscreens are derivatives of cinnamic acid and benzophenone. 

MM Drucker, SJ Blondheim, L Wislicki, Factors affecting acetylation in vivo of para-aminobenzoic acid by human subjects. Clin Sci 27 133-141, 1964. 

PA6,6, 10 208-209, 210 PA11, 10 209, 210 PA12, 10 209, 210 P. A. 3679, thermal resistance characteristics, 8 634t PAAm microgels, 23 746 PABA (para-aminobenzoic acid),... 

PAG , 111 Paludrine, 115 Pamaquine, 345 Papaverine, 347, 348 Para-aminobenzoic acid, in bacterial metabolism, 109, 121 Para-aminosalicylic acid, 109 Paraethoxycaine, 10, 11 Paramethadione, 232 Paramethasone, 200 Parasympathetic nervous system, 35, 62... 

Pharmacology Sulfonamides exert their bacteriostatic action by competitive antagonism of para-aminobenzoic acid (PABA), an essential component in folic acid synthesis. 

Pharmacology SMZ inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid. TMP blocks the production of tetrahydrofolic acid by inhibiting the enzyme dihydrofolate reductase. 

Chemicals in sunscreens work much like melanin to absorb UV radiation. The most common is para-aminobenzoic acid or PABA, but there are others. Most glass, but not clear plastic, will block UV radiation. Relatively simple measures, such as hats and clothing, will greatly reduce exposure. About 90% of UV radiation is reflected by snow, making snow blindness a significant concern. 

Henderson, L., Fedyk, J Bourner, C Windebank, S., Fletcher, S. and Lovell, W. (1994) Photomutagenicity assays in bacteria factors affecting assay design and assessment of photomutagenic potential of para-aminobenzoic acid. Mutagenesis,... 

Sulfanilamides are antibiotics that serve as structural analogs of para-aminobenzoic acid (PABA), a substrate In the formation of folic acid by many bacteria. Substitution of the sulfanilamide compound In place of PABA In the reaction prevents formation of the critical coenzyme folic acid. 

Both the sulfonamides and trimethoprim interfere with bacterial folate metabolism. For purine synthesis tetrahydrofolate is required. It is also a cofactor for the methylation of various amino acids. The formation of dihydrofolate from para-aminobenzoic acid (PABA) is catalyzed by dihydropteroate synthetase. Dihydrofolate is further reduced to tetrahydrofolate by dihydrofolate reductase. Micro organisms require extracellular PABA to form folic acid. Sulfonamides are analogues of PABA. They can enter into the synthesis of folic acid and take the place of PABA. They then competitively inhibit dihydrofolate synthetase resulting in an accumulation of PABA and deficient tetrahydrofolate formation. On the other hand trimethoprim inhibits dihydrofolate... 

Balsalazide (5ASA azo-bonded to para-aminobenzoic acid) 2.25 ... 

Chemical Class Para-aminobenzoic acid derivative Clinical Pharmacology ... 

Brand Name(s) Procanbid, Procan SR, Pronestyl, PronestybSR Chemical Class Para-aminobenzoic acid derivative... 

Mectianism of Action Interferes with synthesis of folic acid that bacteria require for growth by inhibition of para-aminobenzoic acid metabolism. Therapeutic Effect Prevents further bacterial growth. 

Figure 14.2 Chemical structure of folates. Folate molecules consist of pteridine, para-aminobenzoate (pABA), and glutamate moieties. Plants usually contain polyglutamylated forms of folates that are made by the addition of up to about six glutamate residues (which form the y-glutamate tail) attached to the first glutamate, each linked by amide bonds to the preceding molecule of glutamate through the y-carboxyl of the latter. Cl units at various levels of oxidation can be attached to NS and/or N1 0, as indicated by Ri and R2.

Para-aminobenzoic acid (PABA) and its esters, benzophenones IX Acne preparations... 

Antimicrobial sulpha drugs, e.g. sulphanilamide, are the amide of sulpha-nilic acid, and certain related substituted amides. Sulphanilamide, the first of the sulpha drugs, acts by inhibiting the bacterial enzyme that incorporates para-aminobenzoic acid into folic acid. Sulphanilamide is a bacteriostatic drug, i.e. inhibits the further growth of the bacteria. 

To date, over 10 000 structural analogues of sulphanilamide, the parent of all sulpha drugs, have been synthesized and used in the SAR studies. However, only about 40 of them have ever been used as prescribed drugs. Sulpha drugs are bactereostatic, i.e. they inhibit bacterial growth but do not actively kill bacteria. These drugs act on the biosynthetic pathway of tetrahydrofolic acid, inhibit dihydropteroate synthetase and mimic the shape of PABA (para-aminobenzoic acid). 

Later studies concerned the detection of both sulfonamides and sulfonamide potentiators in fish tissues. Mixtures containing ethyl acetate, sodium sulfate, and sodium hydroxide (80), or ethyl acetate and sodium hydroxide (115), have been all used for extracting residues of sulfadiazine and trimethoprim from trout and salmon tissues. In the former approach, para-aminobenzoic acid was employed to neutralize sulfadiazine prior to the microbiological assay of trimethoprim, whereas in the latter approach Bacillus subtilis (ATCC) was directly used for sulfadiazine detection. The limit of detection for sulfadiazine using Bacillus subtilis was found to be 0.04 ppm. The test indicator organism used in both approaches to detect trimethoprim down to 0.1 ppm was Bacillus pumilus (CN60 Welcome Research Laboratories, London) (115,116). 

Procaine, a para-aminobenzoic acid ester, was the first synthetic LA synthesized in 1904. It has a slow onset of action and a short duration and hence low toxicity. Due to its extremely low binding to plasma proteins (only 6 %) procaine is rapidly hydrolyzed by plasma cholinesterases to diethylaminoethanol and para-aminobenzoic acid, which inhibit the actions of salicylates and sulfonamides (Tetzlaff, 2000). 

---