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Xenobiotics are foreign chemical compounds found in living organisms that are not produced naturally or consumed as part of their diet. They can be harmful, but some organisms can develop resistance to them. Human bodies remove xenobiotics through metabolism, which is important in developing new drugs and studying the effects of pollutants.
Xenobiotics are any chemical compounds found in a living organism, but which are foreign to that organism, meaning that it does not normally produce the compound or consume it as part of its diet. For example, in humans, most drugs fall into this category, as people do not produce them naturally or consume them under normal circumstances. Xenobiotics can also be defined as substances present in higher than normal concentrations, or completely artificial and which did not exist before being synthetically produced by man.
A compound normal to one organism may be xenobiotic to another. A commonly used example of this is the effect experienced by fish living downstream from the outlet of a wastewater treatment plant. Human-made hormones can be present, even in treated water, and these compounds are foreign to fish.
When an animal produces a toxin as a defense mechanism against predators, these toxins can also be thought of as xenobiotics from the predator’s perspective. However, predators can also develop defenses against these toxins. An interesting case where this has occurred is in the rough-skinned newt and its predator, the garter snake. Tetrodotoxin is a xenobiotic produced in the body of the newt, which is usually highly poisonous to other animals, but the garter snake has evolved a resistance to continue preying on the newt. It is speculated that as the newt species produced higher and higher concentrations of the venom over the generations, the garter snake developed progressively stronger resistance against it.
When human bodies encounter such a substance, they remove it through a process called xenobiotic metabolism. Through these processes, the chemical structure of the compound is modified and broken down to be used by the body or to be detoxified, in the case of some poisons. Sometimes, it is these chemical pathways and their reactions that can be fatal, as is the case with deaths from poisoning and harmful drug interactions.
The metabolic pathways that the body uses to process foreign substances have long been the subject of great interest in medical science. It is largely through the study of these pathways that new drugs are proposed and developed, especially in the case of chemotherapy drugs used in the treatment of cancer. They are also important in studying the potential effects of pollutants on an environment, to see if the chemical will be broken down or will remain in the environment and cause harm.
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