Secondary metabolite chemical differences between

Importantly, Lindquist et al.53 also document that ascidians can exhibit chemical differences between defensive secondary metabolites among adults and larvae. For example, larvae from colonies of Sigillina cf. signifera contained more tambjamine C, less tambjamine E, and no tambjamine F as compared to adults.65 Moreover, larvae of Trididemnum solidum contain only four of the six didemnins found in adults.53 This could be the result of different selective pressures during planktonic vs. benthic life history phases. In contrast, Lucas et al.44 found no differences in the saponin chemical defenses of the embryos, larvae, and adults of the sea star Acanthaster planci. Clearly, additional studies are needed to expand the evaluation of ontogenetic shifts in defensive chemistry in marine organisms. 

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. 

Examinations of global-scale patterns of secondary metabolite production frequently look at current interactions between existing algae and herbivores and infer past patterns of selective pressures from them.26 6290 91 These studies rarely take into account the evolutionary histories of the algal and herbivore taxa that are common at different sites. Examinations of the evolutionary origins of groups and their dispersal patterns over time may provide valuable insights into the evolution of interactions, patterns of chemical defense concentrations, and selective pressures for the production of chemical defenses. 

We can distinguish between secondary metabolites that are already present prior to an attack or wounding, so-called constitutive compounds, and others that are induced by these processes and made de novo. Inducing agents, which have been termed elicitors by phytopathologists, can be cell wall fragments of microbes, the plant itself, or many other chemical constituents (4,17,22-24). The induced compounds are called phytoalexins, which is merely a functional term, since these compounds often do not differ in structure from constitutive natural products. In another way this term is misleading, since it implies that the induced compound is only active in plant-microbe interactions, whereas in reality it often has multiple functions that include antimicrobial and antiherbivoral properties (see below). 

The difference in secondary metabolites between the three medicinally used Valeriana species imply that the pharmaceuticals prepared from the respective crude drugs also differ largely with regard to their chemical composition. However, legal demands do not exist on this point. Neverthless, several manufacturers have standardised their products, either on valepotriates or on valerenic acid and its derivatives. 

The term elicitor refers to chemicals from various sources, biotic or abiotic, as well as physical factors, that can trigger a response in living organisms resulting in a high accumulation of secondary metabolites. Therefore, elicitors are usefiil tools for improving the production of plant valuable compounds ([36] and references therein). The effectiveness of elicitation as a tool to enhance the production of secondary metabolites depends on a complex interaction between the elicitor and the plant cell. There is evidence that the same elicitor can stimulate secondary metabolism in different cell cultures and that certain plant cultures are responsive to diverse elicitors. Treatment of a particular plant cell culture with different elicitors will result in the accumulation of a particular class of compounds, since these are specific of each plant culture. Although the class of metabolite depends on the plant species, the kinetics of induction or accumulation levels can vary with different elicitors. 

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