Acid-base degradation

If a compound has aqueous solubility problems, should co-solvents be employed to facilitate dissolution for aqueous acid/base degradation studies If so, what co-solvents are recommended7... 

Carprofen and the acidic, basic, and photoirradiated breakdown products were separated on a Cu column (A = 270 nm) using a 50/49/1 acetonitrile/water/acetic acid mobile phase. Photodegradation generated at least seven decomposition compounds, whereas acid/base degradation generated two. Separation was adequate and elution was complete in 15 min (<10 min for carprofen alone). A linear range of 2.5-80 Pg/mL was reported [1342]. 

Absorption of Hydrogen Chloride. Effective heat stabilizers have the abiHty to bind hydrogen chloride. Most stabilizer systems contain one or more metallic soaps or salts which readily undergo a simple acid—base reaction with the by-product hydrogen chloride as the PVC degrades ... 

The tetracycline molecule (1) presents a special challenge with regard to the study of stmcture—activity relationships. The difficulty has been to devise chemical pathways that preserve the BCD ring chromophore and its antibacterial properties. The labiUty of the 6-hydroxy group to acid and base degradation (12,13), plus the ease of epimerization (23) at position 4, contribute to chemical instabiUty under many reaction conditions. 

Leonard and Elderfield have also carried out degradation experiments with alstonine and its tetrahydride. On fusion with potassium hydroxide at 300-350° in nitrogen, alstonine furnishes barman (p. 490) and indefinite basic and acidic fractions. Tetrahydroalstonine on like treatment produces barman, worharman, and three unidentified bases, each of which fluoresces blue in alcoholic hydrochloric acid Base A, C4,H4gN2, m.p. 171-5 to 172-5°, forms a picrate, m.p. > 267° is probably a substituted -carboline. Base B, or 18 3, gives apicrate, m.p. 261° (dec.). Base C,... 

Poly(L-malate) decomposes spontaneously to L-ma-late by ester hydrolysis [2,4,5]. Hydrolytic degradation of the polymer sodium salt at pH 7.0 and 37°C results in a random cleavage of the polymer, the molecular mass decreasing by 50% after a period of 10 h [2]. The rate of hydrolysis is accelerated in acidic and alkaline solutions. This was first noted by changes in the activity of the polymer to inhibit DNA polymerase a of P. polycephalum [4]. The explanation of this phenomenon was that the degradation was slowest between pH 5-9 (Fig. 2) as would be expected if it were acid/base-catalyzed. In choosing a buffer, one should be aware of specific buffer catalysis. We found that the polymer was more stable in phosphate buffer than in Tris/HCl-buffer. 

Kleimnan et al. 2008). In addition, synthetic siRNAs are also subject to degradation in vivo by nuclease activity. Besides side effects and instability, the efficient and specific delivery of the RNAi indncers to the target cell still requires optimization. Here we snmmarize the cnrrent statns of nncleic acid-based antiviral therapentics. The focns will be on antiviral strategies nsing antisense and RNAi technology. Additionally, antiviral ribozymes and aptamers will be discussed briefly, with a focus on recent studies. Gene therapy approaches and delivery systems are the subject of Chapter 11 of this book. 

Skaija GA and Woodhouse KA. S3mthesis and characteization of degradable pol)oirethane elastomers containing an amino acid based chain extender. J Biomater Sci Polym Ed, 1998, 9, 271-295. 

Any polymer that has commercial value must be stable under a variety of conditions. This means that it must not degrade when exposed to light, heat, or a variety of chemicals, including acids, bases, and oxidizing agents. Over time, polymers with superior stability have replaced less stable materials. For example, the first synthetic plastic, celluloid, is so highly flammable that it is no longer an important commercial polymer. 

At times the solubility of a drug in water is insufficient at room temperature to allow a meaningful kinetic study, in which case it can, at times, be carried out at elevated temperature [58]. If done at several different temperatures, it may be possible to estimate the stability at room temperature by extrapolation. Frequently, a broad screen of stability is performed on the initial small sample used for initial performulation this is frequently referred to as forced decomposition studies [59], in which the drug is exposed to acid degradation, base degradation, aqueous degradation, drug powder... 

Acid-base, hydrolysis, hydration, neutralization, oxidation-reduction, polymerization, thermal degradation Adsorption-desorption, precipitation-dissolution, immiscible-phase separation, biodegradation, complexation Acid-base, neutralization, oxidation-reduction (most inorganic and some biologically mediated), adsorption-desorption, precipitation-dissolution, complexation Hydrolysis, oxidation-reduction (biodegradation of anthropogenic inorganics), immiscible-phase separation... 

---