Naturally-occurring chemicals

Chemicals are ubiquitous as air, carbohydrates, enzymes, lipids, minerals, proteins, vitamins, water, and wood. Naturally occurring chemicals are supplemented by man-made substances. There are about 70000 chemicals in use with another 500-1000 added each year. Their properties have been harnessed to enhance the quality of life, e.g. cosmetics, detergents, energy fuels, explosives, fertilizers, foods and drinks, glass, metals, paints, paper, pesticides, pharmaceuticals, plastics, rubber, solvents, textiles thus chemicals are found in virtually all workplaces. Besides the benefits, chemicals also pose dangers to man and the environment. For example ... 

The solubility of most metals is much higher when they exist as organometallic complexes.4445 Naturally occurring chemicals that can partially complex with metal compounds and increase the solubility of the metal include aliphatic acids, aromatic acids, alcohols, aldehydes, ketones, amines, aromatic hydrocarbons, esters, ethers, and phenols. Several complexation processes, including chelation and hydration, can occur in the deep-well environment. 

Radon is a naturally occurring, chemically inert, radioactive gas. It is colorless, odorless, and tasteless. It is part of the uranium-238 decay series, the direct decay product of radium-226. Radon moves to the earth s surface through tiny openings and cracks in soil and rocks. High concentrations of radon can be found in soils derived from uranium-bearing rocks, such as pitchblende and some... 

Clearly, in many cases, cancer is the result of the action of synthetic and naturally occurring chemical species. The role of chemicals in causing cancer is called chemical carcinogenesis. It is often regarded as the single most important facet of toxicology and clearly the one that receives the most publicity. 

A specialty of geology concerned with earth processes, earth resources, and engineering properties of earth materials and relevant to (1) the protection of human health and natural ecosystems from adverse biochemical and/or geochemical reactions to naturally occurring chemicals or to chemical compounds released into the environment by human activities and (2) the protection of life, safety, and well-being of humans from natural processes, such as floods, hurricanes, earthquakes and landslides, through land-use planning. 

They are added for specific purposes (e.g. to preserve or sweeten food). Growing pressure to use natural substances to meet such needs has led to surprisingly little discussion about the relative safety of naturally-occurring substitutes as opposed to synthetic additives. For example, although synthetic additives should be more easy to produce in purified form, naturally-occurring chemicals may be more acceptable to some members of the public. 

While analytical science is in many ways quite miraculous, it is by no means without problems. Errors can easily be made. Analyses are not always readily reproducible in different laboratories. Some technologies are exceedingly expensive. And while analytical methods are well worked out for many chemicals, they are not available at all for many more. (Indeed, if we are interested in the naturally occurring chemicals that human beings are exposed to, we will find that only a tiny fraction of these can now be analyzed for with anything except fairly sophisticated research tools most such chemicals are still unknown,... 

To further this discussion let us divide environmental chemicals into three broad groups. First there is the enormous group of naturally occurring chemicals that reach us primarily through food and products such as cosmetics, but also through other media. Second are industrially produced chemicals that are manufactured for specific purposes. And third are the industrial pollutants - chemical byproducts of fuel use, the chemical industry, and most other types of manufacturing. 

This exciting manuscript, for the first time, details the plethora of biological activities of this fascinating group of naturally occurring chemicals. We hope that this provides a one-stop reference for scientists to gain a fuller understanding of bile-acid activity and function. 

Rhenium was the last naturally occurring chemical element to be discovered in 1925 by Noddack, Tacke, and Berg in the mineral gadolinite. The name of this extremely rare element (the estimated occurrence in the earth s crust is about 0.7 ppb ) is derived from the Rhine river. Residues from the processing of molybdenum ores represent the main source of the metal. 

At this point in the presentation, our picture of stellar evolution and the nucleosynthesis of naturally occurring chemical elements is almost complete. Many reflnements would be required to give a fuller view. In fact, many pieces of the jigsaw are still missing or inadequately understood, in particular with regard to the r process. Despite all this, we have tried to convince the reader that the nucleosynthesis model constitutes a fundamental opus of the human intellect. 

When the French chemist Antoine Lavoisier published his famous list of elements in 1789, there were only 33 elements, several of which were erroneous. By 1930, the diligent labors of thousands of chemists had increased the tally of naturally occurring chemical elements to 90. More recently, physicists in high-energy laboratories have been able to create about 20 highly radioactive, unstable elements that do not exist naturally on Earth, although they are probably produced in the hot cores of some stars. 

In a recent literature survey of chromenes and benzofurans in flowering plants, we have documented that approximately 90% of the 200 compounds Isolated are present in the sunflower family (Asteraceae). These naturally occurring chemicals have recently received considerable attention because of their potent cytotoxic and insecticidal activity. Chemotaxonomlcally, not all tribes of the Asteraceae seem to produce chromenes or benzofurans, with the major tribes capable of synthesizing chromenes identified as the Eupatorleae, Hellantheae, Inuleae, Senecloneae and the Astereae (17). 

Non-nature-identical chemicals should be further categorized according to what we know about how they fit into natural processes and cycles and according to their persistence and mobility. The latter characteristics both increase the riskiness of novel chemicals. It is less clear that they make a naturally occurring chemical more risky, however rather they are properties that, like the other properties of the chemical, enable it to perform its function in natural systems and processes. 

The series Volume 3 Anthropogenic Compounds describes synthetic compounds, and compound classes as well as elements and naturally occurring chemical entities which are mobilized by man s activities. 

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