Secondary metabolites mammals

Thus, there is an interesting contrast between terrestrial and marine systems in the relationship between specialization and detoxification of secondary metabolites. Among terrestrial insects and mammals, specialists seem to be associated with chemically difficult plants (Berenbaum et al. 1996), while in marine systems, generalists tend to consume chemically rich plants (e.g., amphipods and fishes). 

How much a mammal eats of a given plant often depends on the levels of different classes of chemical constituent, notably nutrients and plant secondary metabolites. As in birds, it is not the plant defense compounds alone, but rather complex balances between nitrogen and carbohydrate contents, levels of defense compounds, and fiber that determine palatability. 

Alcohols are oxidized to aldehydes by the liver enzyme alcohol dehydrogenase, and aldehydes to carboxylic acids by aldehyde dehydrogenase. In mammals, monooxygenases can be induced by plant secondary metabolites such as a-pinene, caffeine, or isobornyl acetate. Reduction is less common and plays a role with ketones that cannot be further oxidized. Hydrolysis, the degradation of a compound with addition of water, is also less common than oxidation. 

Foley, W. J., McLean, S., and Cork, S. J. (1995). Consequences of biotransformation of plant secondary metabolites on acid-base metabolism in mammals a final common pathway Journal of Chemical Ecology 21,721-743. 

In the forgiveness of any theological position, this inqilies that rapid extinction of natural-product-rich species goes to the detriment of the Earth s present equilibrium more than the disappearance of species that produce trivial secondary metabolites. From this viewpoint, the loss of microbes matters much more than the loss of the great mammals or man. 

Many coumarins are found in plants and a comprehensive review is available (78FOR(35)i99). Coumarin has a pleasant taste and odour and was used for flavouring until its toxic action on the liver was discovered. Among other coumarins which have toxic effects on mammals are a group called aflatoxins, e.g. aflatoxin Gi, (221), which are secondary metabolites of fungi of the Aspergillus genus. Some of these compounds have been present in animal feeds and caused deaths of the animals. In contrast, other coumarin derivatives,... 

The biological functions of such plant secondary metabolites (PSMs) have been debated for a long time. They often have antimicrobial functions, but also serve as repellents and feeding inhibitors against herbivorous insects and vertebrates, notably birds and mammals. Animals have evolved many mechanisms to cope with phenolics in their diet. These start with food processing. For instance, beavers consume experimental sticks of the phenolics-rich witch hazel only after leaving them in the water for 2-3 days, apparently to leach out unpalatable compounds (Miiller-Schwarze et al. 2001). Many birds and mammals eat clay to adsorb phenolics so they never will be absorbed in the intestines. If they are taken up in the blood stream, such PSMs will eventually be rendered harmless by oxidation and other processes, followed by conjugation, in the liver. They then will be excreted in the urine. 

In comparison with mammals, plants contain considerably more GTs because, in addition to the reactions carried out by mammalian GTs, they are required to convert the products of photosynthesis into diverse cell carbohydrates. For example, these GTs synthesize cell wall polysaccharides as well as secondary metabolites and xenobiotics. Plant GTs differ from mammalian GTs even more by their diversity of nucleotide donors. They use not only eight of the nine mammalian nucleotide donors, but numerous others such as UDP-L-rhamnose, GDP-L-glucose, GDP-L-galactose, UDP-L-arabinose, UDP-D-galacturonic acid, UDP-D-apiose, and so on. (29). 

Many attempts have been made to find cholesterol biosynthesis inhibitors for development as hypocholesterolemic agents. Microbial secondary metabolites have been used as valuable natural sources in the development of novel cholesterol biosynthesis inhibitors. Mevastatin and lovastatin were isolated from the fungi, Penicillium citrinum and Aspergillus terreus, respectively, as potent inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase which is involved in the rate-limiting step of cholesterol synthesis in mammals. These findings have led to the development of statins , which are drugs of choice in the treatment of hypercholesterolemia. 

The jasmonoids are secondary metabolites of the fatty acid metabolism. Jasmonates play a role in signal transduction in plants, similar to that of the structurally related prostaglandins in mammals. 

Prostaglandins, e.g. prostaglandin 3 (7./9), are physiologically active secondary metabolites found in mammals. The biosynthesis of these compounds also involves an unsaturated fatty acid, e.g. arachidonic acid 1.17), Formation of the characteristic prostaglandin skeleton involves the formation of an intermediate endoperoxide 1.18). Some of the succeeding steps are indicated in Scheme 1.4 [8-10]. 

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