Significance of Degradation

Koster, J. Turnover and degradation of secondary (natural) products. In The Biochemistry of Plants, Vol. 7, Secondary Plant Products (E. E. Conn, ed.), pp. 35-84. Academic Press, New York 1981 

Robinson, T. Metabolism and function of alkaloids in plants. Science 184, 430-435 (1974) Seigler, D. S, Primary roles for secondary compounds. Biochem. Syst. Ecol. 5, 195-199 (1977) Waller, G. R., Nowacki, E. K. Alkaloid Biology and Metabolism in Plants. Plenum Press, New York 1978 

Zaprometov, M. N. Metabolism of phenolic compounds in plants (Russ.). Biochimija 42, 3-20 (1977) 

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This ratio may also be estimated from a deteimination of the amount of initiator residues found in the monomer. From such data the significance of degradative chain-transfer in an allyl ester polymerization can be judged. For example, it was found that in the allyl ethyl carbonate polymerization, degradative chain-transfer predominates, whereas in the polymerization of allyl laurate and allyl benzoate, effective chain-transfer predominates [19]. 

Cumene is expected to exist almost entirely in the vapor phase in the atmosphere (13). In water, mixed cultures of microorganisms collected from various locations and depths in the Atiantic Ocean were all found to be capable of degrading cumene (14). A number of studies have examined the aerobic degradation of cumene in seawater and in groundwater (15,16). The results indicate that cumene would normally be naturally degraded to below detectable limits within a week to ten days. Cumene is tightly adsorbed by soil and is not significantly mobile in soil (17). 

The mechanisms of degradation and the mode of action of the various PVC stabilisers have both been widely studied. Often at least one aspect of their operation is some sort of reaction with the first trace of hydrogen chloride evolved. This removes what would otherwise act as the catalyst for further dehydrochlorination, and hence significantly retards the degradation process. In addition, many stabilisers are themselves capable of reacting across any double bonds formed, thereby reversing the process that causes discoloration and embrittlement. 

Results from other studies support the rapid degradation of methyl parathion in soils with a high water (i.e., low oxygen) content (Adhya et al. 1981, 1987 Brahmaprakash et al. 1987). Experiments in flooded and nonflooded soils showed that the redox potential affected both the rate of degradation and the transformation products of methyl parathion (Adhya et al. 1981, 1987). Transformation to volatile products was suggested by Brahmaprakash et al. (1987) as the reason that significant amounts of " C from labeled methyl parathion could not be accounted for, especially in flooded soils. 

An environmental protocol has been developed to assess the significance of newly discovered hazardous substances that might enter soil, water, and the food chain. Using established laboratory procedures and C-labeled 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), gas chromatography, and mass spectrometry, we determined mobility of TCDD by soil TLC in five soils, rate and amount of plant uptake in oats and soybeans, photodecomposition rate and nature of the products, persistence in two soils at 1,10, and 100 ppm, and metabolism rate in soils. We found that TCDD is immobile in soils, not readily taken up by plants, subject to photodecomposition, persistent in soils, and slowly degraded in soils to polar metabolites. Subsequent studies revealed that the environmental contamination by TCDD is extremely small and not detectable in biological samples. 

Hdrtensteiner, S. et ah, Evolution of chlorophyll degradation the significance of RCC reductase, Plant Biol, 2, 63, 2000. 

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