Natural compounds typically have complex structures not easily obtained by synthetic chemistry. Often however, the natural compound needs to be modified synthetically to enhance its desirable medicinal properties, or to reduce its toxic properties. Many useful medicinal agents are obtained by total synthesis. A chemist interested in developing a new drug for a particular disease has the option of starting with a naturally occurring substance or with more basic raw materials.
Anti-cancer agents are a particular therapeutic class for which natural products have been important. Many of these compounds, such as paclitaxel and adriamycin, were originally obtained from plant or microbial sources. Because of their complex structures, they are difficult to make synthetically and are still obtained from natural sources.
Yet numerous drugs have been improved over the years through modification by synthetic chemists. Antibiotics such as penicillin and erythromycin are obtained from natural substances and modified synthetically to generate the desired effects.
Other important agents in use today are made by total synthesis, such as the quinolone antibacterial, ciprofloxacin. All drugs used to treat HIV and herpes infections are made synthetically; the use of natural products for the treatment of viral diseases has had very limited success.
Herbal medicines are a special class of drugs. They are usually complex, multi-component mixtures that are not well-characterized or understood. The conditions under which the plant is grown and the isolation procedure used can result in product variance dependent on the particular plant source. Since composition can vary, so may the therapeutic effectiveness and the untoward effects. Even though herbal medicines have been around for ages, the understanding of them is only in its infancy; future research may provide significant benefits for the discovery of new drugs.
Vitamins, essential for proper nutrition, may be obtained naturally or synthetically. Despite considerable promotion of the idea that natural vitamin sources are more beneficial than those produced synthetically, many vitamins, such as Vitamin C, are synthesized in a "nature-identical" form.
The toxicity of certain substances and their potential use in chemical warfare has received considerable recent attention. The toxicity of a compound is not a function of its natural or synthetic origin. Extremely toxic substances, such as botulinum toxin and ricin, may be obtained from natural sources. The toxicity of a compound is generally related to its dose level, and even the most toxic substance (Botox) can have medically useful properties in minute doses.
The safety and efficacy of a drug molecule is a function of its chemical structure, not its origin. The molecular structure defines its interactions with other molecules in the body, and is the reason why a substance exhibits desirable or undesirable activities. Whether the compound is of natural or synthetic origin is irrelevant.
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Official Summary written by Dr. Thomas Perun, Professor Paul Erhardt, and Dr. James McAlpine To view the original article, visit http://www.iupac.org/publications/pac/2002/7410/7410x1957.html
For questions, contact Laura Abernathy, IUPAC Communications Specialist, Laura@iupac.org
Journal
Pure and Applied Chemistry