Plant secondary chemicals function

Secondary chemistry differs from primary chemistry principally in its distributional variability and it is this variability that has intrigued ecologists for the past 30 years. Theories [or provisional hypotheses (35)] to account for the structural differentiation and function of secondary metabolites, as well as the differential allocation of energy and materials to defensive chemistry, abound, but they are almost exclusively derived from studies of plant-herbivore interactions (Table 2). This emphasis may be because the function of secondary chemicals in plants is less immediately apparent to humans, who have historically consumed a broad array of plants without ill effects, so alternative explanations of their presence readily come to mind. The fact that animals upon disturbance often squirt, dribble, spray, or otherwise release noxious substances at humans and cause pain leads to readier acceptance of a defensive function [although there are skeptics who are unconvinced of a... 

Cyanobacterial toxins (both marine and freshwater) are functionally and chemically a diverse group of secondary chemicals. They show structure and function similarities to higher plant and algal toxins. Of particular importance to this publication is the production of toxins which appear to be identical with saxitoxin and neosaxitoxin. Since these are the primary toxins involved in cases of paralytic shellfish poisons, these aphantoxins could be a source of PSP standards and the study of their production by Aphanizomenon can provide information on the biosynthesis of PSP s. The cyanobacteria toxins have not received extensive attention since they have fewer vectors by which they come in contact with humans. As freshwater supplies become more eutrophicated and as cyanobacteria are increasingly used as a source of single cell protein toxic cyanobacteria will have increased importance (39). The study of these cyanobacterial toxins can contribute to a better understanding of seafood poisons. 

Plants possess an incredibly diverse biosynthetic capacity leading to the production of a myriad of compounds that, although not having an apparent function for fundamental life processes (growth, development and reproduction), seem to have vital roles as mediators of ecological interactions, being very important for the survival of plants. This chemical wealth is the basis of the use of plants in medicine, and is still largely unexplored. One example of application of the so called plant secondary metabolites are the terpenoid indole alkaloids of Catharanthus rose us, used in cancer therapy, and known as the Vinca alkaloids. 

Pyrrolizidine alkaloids (PAs) are typical constitutively produced plant secondary compounds. PAs exist in a great diversity of some 370 chemical structures [1-3]. They are assiuned to have evolved as chemical defenses under the selection pressure of competing herbivores. This is evidenced by a number of insect herbivores from imrelated taxa which have developed adaptations not only to overcome PA-mediated plant defense, but also to sequester and utilize these alkaloids for their own defense against predators. PAs are an excellent choice to exemplify mechanistic and functional aspects of plant secondary metabolism [4,5]. 

In addition to the careful selection of structural metals, the cathodic protection of water-wetted parts may also be specified. For most boiler plant systems, however, because of the tortuous and extended waterside surfaces involved, the use of cathodic protection is only a partial solution to controlling corrosion and should never be the sole secondary protocol. Rather, cathodic protection functions well when employed as part of a more comprehensive program that includes appropriate internal chemical treatments. 

In recent years, extensive attention has been focused on finding cultured plant cells that can be used as catalysts for organic functional group transformations. A number of transformations employing freely suspended or immobilized plant cell cultures have been reported.24 For example, Akakabe et al.25 report that immobilized cells of Daucus carota from carrot can be used to reduce prochiral carbonyl substrates such as keto esters, aromatic ketones, and heterocyclic ketones to the corresponding secondary alcohols in ( -configuration with enantiomeric excess of 52-99% and chemical yields of 30 63%). 

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