For thousands of years humans turned to nature to cure and soothe their ills. Modern science built on these ancient foundations and the natural product discovery programmes to be defined by pharmaceutical companies provided us with medications that could treat cancer, infections and more.
But discovering medicines may be in nature is far from straightforward. Its hard enough to gather sufficient numbers of the useful organism, whether that has become a tree root or a venomous serpent, and its even harder to isolate the exact medicinal compound and then produce it in large quantities.
With all these stumbling blocks its no surprise that pharmaceutical companies shifted their focus from nature to the laboratory and began designing compounds from scratch, huge numbers of which could then be screened for promising activity. From the 1990 s onwards the pharmaceutical companies duly terminated their nature discovery programmes and the enormous collections of screening extracts they amassed were sold or disbanded.
Recent developments in genetics have prompted a shifting back towards natural products, however. Scientists can now mine an organisms entire Dna to search for useful compounds, and it is becoming increasingly evident that we have scarcely scratched the surface of natures molecular diversity, which has been sharpened by more than three billion years of trial and error. There are many more medications still undiscovered, lurking within plants, animals, fungi and bacteria. This realisation, and looming health crises like the rise of antibiotic resistance, has renewed interest in the search for useful compounds in nature known as bioprospecting.
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Most nature-derived medications today are sourced from plants, fungus and bacteria. Those medications that have been removed from animals have largely come from simply a few sources: venomous vertebrates like the gila ogre lizard or jararaca serpents, leech saliva, or the venoms and secretions of organisms like sponges or molluscs. But animals are incredibly diverse, and weve scarcely tapped into the potential pharmaceutical employ of the most diverse group of all insects.
Insects are full of useful compounds
Insects occupy every conceivable terrestrial and freshwater niche on Earth. Consequently, they have a bewildering array of interactions with other organisms, which has meant theyve evolved an enormous variety of compounds to protect themselves or for preying on others.
Of the tiny proportion of insects that have been investigated, several interesting compounds have been identified. For instance, alloferon, an antimicrobial compound being developed by blow fly larvae, is used as an antiviral and antitumour agent in South Korea and Russia. The larvae of a few other insect species are being investigated for potent antimicrobials. Beyond flies, a compound sourced from the venom of the wasp Polybia paulista can kill cancer cells without harming normal cells.
So why is it that bioprospectors have paid relatively little attention to insects? The sheer range is partly to blame with many millions of species to search through, find a useful insect is like looking for a needle in a haystack. And though we consider insects to be everywhere, the reality of this ubiquity is vast numbers of a few extremely common species. Most bugs are hard to find and very difficult to rear in captivity.
And even when a useful species has been identified and reared successfully, its still incredibly difficult to obtain sufficient sums of the relevant material. Insects are generally very small and the glands inside them that secrete interesting, potentially useful compounds are smaller still.
The search for friendly bugs
The good news is that we can overcome some of these difficulties by utilizing knowledge of natural history to target our efforts. Myself and David Wilcockson at Aberystwyth University term this approach ecology-led narcotic discovery.
Many bugs advertise the production of potentially useful compounds in the way in which they live and where they live. Some produce potent, complex venom for subduing prey and maintaining it fresh for their progeny. Others are masters at exploiting filthy micro-habitats, such as faeces and carcass, where they are regularly challenged by myriad micro-organisms. The insects in both these instances have a battery of antimicrobial compounds to deal with pathogenic bacteria and fungus that are likely serve as or inspire new antibiotics for humans.
Although natural history knowledge phases us in the right direction it doesnt solve the problems associated with the smaller sizing of bugs and the tiny quantities of interesting compounds they create. Fortunately, it is now possible to identify and then snip out the stretchings of the insects DNA that carry the codes for the interesting compounds and insert them into cell lines that allow larger quantities to be produced.
As much as Id dearly love to help develop a blockbuster insect-derived medication, my main motivation for looking at bugs in this way is preservation I want narcotics from glitches to make funding for basic exploration, species discovery and natural history. All species, however small and seemingly insignificant, have a right to exist for their own sake, but this sentiment lacks the political clout needed to fight for the urgent preservation of nature. We require something more tangible, something that is directly relevant to people, and you would be hard pressed to find anything that is held so dear as health.
If we can shine a light on the darker recess of natures medicine cabinet, exploring the useful chemistry of the most diverse animals on countries around the world, I believe we can induce people think differently about the value of nature.