Light degradation product

The 1,4-dUiydropyridines, for example, nifedipine, nicardipine and amlodip-ine, are a well-established class of anti-hypertensive drugs. They are photolabile, some markedly so, for example, nifedipine. In all cases, the major light degradation product is the resonance-stabilised, fuUy aromatic, pyridine analogue [38]. 

In rabbits under light amytal anesthesia, chlordan has no direcr effect on the blood pressure, but produces a type of respiration having many characteristics in common with Cheyne-Stokes type. The generalized tremors, opisthotonus, tonic and clonic convulsions, produced by chlordan were decreased or abolished and respiration restored to normal by suitable injections of the sodium salts of amytal, phenobarbital, and pentothal. The LD60 of chlordan, which was about 20 mg. per kg. on intravenous administration to intact rabbits, was increased to about 60 mg. per kg. through the antidotal action of the barbiturates. An unidentified chlorine-containing degradation product with acidic properties was recovered from the urine of rabbits treated with chlordan. Approximately one third of its chlorine content was set free on hydrolysis at 100° C. with sodium hydroxide in either absolute alcohol or in water. 

The mechanisms of photochemical degradation of a polymer are rather difficult to study as the observed degradation is typically a result of the effect of light on the contaminants in the polymer rather than the pure polymer. Studies typically look for the degradation products, either low molecular weight volatiles or radicals, or work to identify the wavelength of light absorbed by the system via spectroscopic methods. 

It may be speculated that in the previously mentioned study on ARPE-19 cells exposed to lutein of low purity (Kanofsky and Sima, 2006), the apparent cytotoxic effects observed in dark that are exacerbated upon irradiation of lutein-laden cells with blue or green light may have been caused by (some) degradation products of lutein. 

Rozanowski, B and Rozanowska, M, 2005. Degradation products of xanthophyll include blue-light absorbing photosensitizers. Invest Ophthalmol Vis Sci 46, E-Abstract 3032. 

If no references for the degradation products or impurities are available in the laboratory, the sample should be exposed to stress conditions such as heat (50-80 °C), ultraviolet light (2000 lux), acid and base (0.1-1 M HC1 and NaOH), and oxidant (3% H2O2). After incubation in the allotted time, the purity and identity of the analyte peak/spot should be proved by using DAD or MS detection (for LC), MS (for GC), or in situ UV-Vis measurement using a densitometry or TLC-MALDI MS (for TLC). 

However, in the light of the results presented herein, this cannot be stated unequivocally, otherwise it would follow that only guaiacyl type compounds would be obtained as softwood lignin degradation products. It has been found that the native lignin from the softwood white Scots pine also yields p-hydroxybenzaldehyde upon oxidation. Thus, it seems that either coniferyl alcohol is not the only lignin progenitor in woody tissues, or that this coniferyl compound is preceded in the process of... 

Figure 10.13 Hyphae of Fusarium alkanophllum from light hydrocarbons producing important amounts of metabolic water from the substrate. In cultures for more than 90 days, drops of water associated to the soluble degraded products were observed. Scale = 10.5 xm (Light Microscope image). (Reproduced from Marcanoa, 2002, by permission of Elsevier)...

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