The Wonders of Natural Products

Photos from UAB in Antarctica group on Flickr, related to this post
By Kate
Posted on 05/18/10

Many of the products that we use in everyday life are made with components of marine organisms. For instance, in face creams green algae is used as a detoxifying agent. Many food products contain carrageenan, a polysaccharide (chain of sugars) extracted from red algae, that’s used to firm ice cream. We call compounds or chemicals that are extracted from organisms natural products. In Antarctica we’re studying natural products as well, though we call them ‘secondary metabolites’ (more on that later).

   A ‘metabolite’ is a molecule which is a product of metabolism; the process of breaking down molecules and creating new ones. The definition of a molecule is a group of at least two atoms which are chemically bonded together. To understand metabolism think about the digestion of food. When you eat sugars, these are broken down from being large molecules to small ones plus energy for your body to work. This energy goes to creating new molecules which aid your body in natural functions. In order to create molecules there is a process of reactions called a biosynthetic pathway and the end product is called a ‘metabolite’. So why do we call the molecules studied here secondary metabolites?

   A primary metabolite is a molecule that is needed in the basic functioning of a body. An enzyme in your mouth is a good example of this. An enzyme is a molecule which aids in a reaction allowing it to take place faster, so that when you eat a cookie, metabolism of the sugars occurs within hours rather than days. Secondary metabolites are molecules which are not needed in basic functioning (i.e., primary metabolism) of your body. These could be chemicals that help in chemical communication or defense of an organism, and we are most familiar with drugs like caffeine which are produced by plants.

   As Maggie and Chuck previously mentioned, Alan and Jason are chemists from USF.  They both study the secondary metabolites derived from the Antarctic invertebrates and algae found around Palmer Station. How do they go from sponge or algae to secondary metabolites? A secondary metabolite is isolated by freeze-drying the algae or invertebrate then removing the water (these are very wet organisms to begin with). Then the organisms are immersed in various chemicals to extract two types of molecules: lipophilic (fat-loving) and hydrophilic (water-loving). The resulting extract is then used in many analyses which include feeding experiments with amphipods, testing by various agencies against common diseases as Maggie mentioned, or a variety of techniques which can determine the structure of the molecule they’re looking at.

   Jason is primarily working with feeding assays to determine whether chemical compounds from the tunicate Synoicum adaraneum are active against its herbivores. He is trying to determine the role this chemical plays in protecting the organism, rather than the role it may have in protecting us.

   As you know from Maggie’s posts, the most common predators in this marine community are amphipods and they need to shed their hard exoskeleton, or molt, frequently. Because of the similarities between structure of the chemical used by amphipods to instigate molting and the chemical produced by the tunicate, it is thought that if the tunicate was eaten by the amphipod it would stop the pod from molting or make it molt before it was ready otherwise, thereby killing it. Good defense.

   Alan is currently working on two projects here at Palmer. The first deals with an alga called Gigartina skottsbergii. Although it is probably really a different species from the one we have here, a species by this name is commonly farmed in Chile for its carrageenans and also is used as a component in over the counter flu medicine. His studies have discovered that a protein in G. skottsbergii is active against the influenza virus including the notorious H1N1.

   Alan’s second project deals with a common nudibranch (a type of shell-less mollusk) found around Palmer station, Austrodoris kerguelenensis. This nudibranch is common around the continent of Antarctica and has no known predators. Having no external shell like other Gastropods (snails), reason expects that this animal must have some other means of protecting itself. Also interesting about this animal is that it comes in a range of sizes and hues from different sites around Palmer station.

   So, thanks to the chemists we have insight into how organisms are defending themselves and evolving that both parallels biological methods and makes the ecological story much more interesting. This involves a lot of lab work, which you may not expect when doing ‘field work’ but provides invaluable insight into the communities here at Palmer.

 

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