Sources of natural products

Natural products are chemical compounds or substances produced by living organisms. They are products of metabolism in living cells. Some of these compounds have biological activities or bioactivities that are useful to us as medicines. Other natural products have utility as renewable bio-based solutions for various applications.

There is a wide variety of sources of natural products and here are some examples.

Plants

Plants have always been a source of natural products for humanity. For example, plants provide us with food. Through photosynthesis, plants use sunlight, water and carbon dioxide to create energy in the form of sugars, releasing oxygen as a by-product. These sugars are used to construct more complex carbohydrates.

The products of plant metabolism (metabolites) can have effects in the body that we can harness for the prevention and treatment of disease, which is why plants are a prolific source of medicines. Bioactive substances can be found throughout a plant or in particular plant parts such as the root, leaves, flower, fruit, bark and so on.

How are plants used in medicine? Herbal medicine uses a plant, part of a plant or an extract from the plant. Herbal medicine preparations are generally complex, containing many different compounds. A compound is a substance made up of two or more different chemical elements. Often, the component responsible for the desired biological effect is identified and isolated as a single compound. Such compounds can be developed further through pharmaceutical research.

A host of pharmaceutical breakthroughs have been developed from plant sources. Plants also provide construction materials and textiles and offer alternatives to fossil fuel-based products such as biodegradable and compostable bioplastics. Plants can also provide us with renewable biofuel and starting materials for the production of industrial chemicals.

Microorganisms

Microorganisms (or microbes) are living things that are too small to be seen with the naked eye but exist all around us. Antibiotics are created with the purpose of targeting certain microbes. The Nobel Prize laureate and microbiologist, Selman Waksman, defined an antibiotic as ‘a compound made by a microbe to destroy other microbes’. Waksman’s research group discovered the antibiotic streptomycin. Indeed, during the golden age of antibiotic drug discovery of the mid-20th century 70-80% of all discovered antibiotics came from a single genus of soil bacteria.

In addition to the natural products they produce, microorganisms perform essential actions in industrial processes. These tiny organisms facilitate production of biofuels, bioplastics and biochemicals and provide enzymes for biotechnologies.

Marine organisms

The ocean is a rich source of unique natural products. Marine invertebrates, such as sponges, corals and mollusks produce bioactive compounds not found in terrestrial organisms. Marine algae also produce useful natural products including fats and antioxidants.

The marine provides us with food and food supplements through fish, fish oil and algal species and a range of ingredients for the food and pharmaceutical industries. Like terrestrial plants, the marine is also a source of materials for the production of energy and renewable, biodegradable materials.

Animals

Some natural product therapeutics are derived directly from animals. Venoms and toxins from snakes, spiders, scorpions, frogs and other animals have potent bioactivities that can have utility in research or potential for drug development. Animals are a source of food for us.

Fungi

Edible mushrooms are a nutritious food source. Like the natural sources above, fungi have been sources of medicines such as antibiotics and natural products with industrial applications. Certain fungi such as brewer’s yeast ferment sugars into ethanol for the beverage industry and for production of biofuel. They can also be used to create biodegradable materials for packaging, building materials and textiles offering sustainable alternatives to plastic, styrofoam and traditional construction materials.

Endophytic microorganisms and symbionts

An endophyte is any microbe (typically fungal or bacterial) that lives inside plant tissues without causing disease or harm. Some bioactive natural products discovered in plants are actually produced by the endophytes living in them. Camptothecin, a precursor for anticancer drugs like topotecan, was originally found in the Chinese tree Camptotheca acuminata and is produced by endophytic fungi in the tree.

Symbiosis is the interaction between organisms of different species living in close physical association, typically to the advantage of both. Lichens are symbiotic associations between fungi and algae or cyanobacteria. Plant root systems are colonized by microbes and these associations can help plant growth and stress tolerance. Plant-microbe symbiosis can facilitate nitrogen fixation and is being explored for potential in sustainable agriculture.