Dr Michelle Dickinson: nanotechnologist on the new research revealing the most bitter tasting substance ever

Bitter flavours act as nature’s warning signs, evolved over hundreds of millions of years to steer us away from potentially toxic compounds.

New research published this week in the Journal of Agricultural and Food Chemistry has just identified the most potent natural bitter compounds known to date and with it insights into why bitterness is so important. 

The star of this discovery is the mushroom Amaropostia stiptica, a non-toxic fungus renowned among foragers for its relentless, mouth-puckering bitterness. 

By guiding their isolation efforts with taste assays, the researchers extracted and characterised three previously unknown triterpene glucosides from this mushroom. 

Among the trio of new compounds, oligoporin D stole the show. In cell-based assays, oligoporin D activated the human bitter taste receptor TAS2R46 at astonishingly low concentrations of around 63 millionths of a gram per litre (roughly one gram dissolved in the volume of a million bathtubs) 

Why does this matter? 

Most entries in BitterDB hail from plants or human-made chemicals. Adding fungal compounds like oligoporin D enriches our chemical map of bitterness, revealing new scaffolds that challenge existing predictive models of taste receptor activation 

Bitter taste receptors predate flowering plants by some 300 million years. By discovering a potent fungal bitterant, researchers gain clues about ancient ecological interactions, did early vertebrates encounter fungi that drove the diversification of their taste receptors? 

Bitter receptors aren’t confined to our mouths - they’re sprinkled throughout the gut, lungs, heart, and even on blood cells. Understanding how natural bitterants like oligoporin D engage these extraoral receptors could unlock new avenues in digestion, immunity, and respiratory health 

The discovery of oligoporin D opens doors to practical innovations including the development of a natural, ultra-bitter coating for household chemicals or pharmaceuticals to prevent accidental ingestion. 

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Episode Transcript

Speaker 1 (00:06):
You're listening to the Sunday Session podcast with Francesca Rudgin
from News talks 'b.

Speaker 2 (00:13):
And with our science study of the week. Doctor Micheldikinson
joins me, Now, good morning, good morning. This is an
interesting one.

Speaker 3 (00:18):
Do you like bitter things and not really no, neither
like a milk chocolate girl's sign, right, yeah, some people
love it.

Speaker 2 (00:26):
I'm going to try the dark chocolate because that's what
you're supposed to have.

Speaker 3 (00:30):
Like franchise, but just have a smaller bit and have
the one that you like. That's what I say. So
here's this news study and if you want to read
it at home this week, it is open source so
you can. And it's in the Journal of Agricultural and
Food Compound Chemistry. It's a lovely little study. It's an
easy read. But basically, scientists have just found the world's
most bitter tasting substance ever. And that's a pretty hard call.

(00:54):
But this thing is disgusting. So why are things bitter?
Usually bitter flavors are in plants and things or you know,
animals to say don't eat me, I'm toxic. So it
was designed as nature's warning sign. And we know that
bitter tastes have sort of evolve over hundreds of millions
of years to help humans and mammals steer away from
toxic things and stop dying. So it's a clever way

(01:16):
that nature has been working together. And the most potent
natural bitter compound but has just been found is unusually,
because it's usually found in plants, has just been found
in a mushroom. And what I find so ironic is
this is a non toxic mushroom.

Speaker 2 (01:34):
It's the thing.

Speaker 3 (01:35):
It doesn't make any sense.

Speaker 2 (01:36):
So did any of them try it?

Speaker 3 (01:38):
Oh? Yeah, so it's a mushroom that people have actually
foragers have known about this mushroom. Okay, and I've gone
on that taste discrip, but some people like that bitterness.
They've liked it, but they've eaten it, and I've gone,
did you know with the alarm bells? Not going, don't
eat me anyway. So they've just tested it and it
is absolutely revolting. It's called a marrow posterious stepka. It's

(01:59):
the type of mushroom totally non toxic. And so what
scientists did is took this very bitter tasting mushroom and
basically chemically broke it up to work out what is
it in there that's making it bitter. And they found
these are called glucosides, and the one that they found
that is the one that is magical here. It's called
oligo pour in D. Now they found D, E, and F,

(02:22):
but D is the one here that we're interested in.
We've never found this before. This is a brand new
compound that has been found and it's activated our bitter
taste receptor. And it's a specific one if you care
about this stuff. It's called TAS two R forty six
and it's activated it at incredibly low concentrations. And I
read it and it said, oh you know, it can

(02:43):
activate it on our tongue at sixty three millions of
a gram per liter. And I'm like, that won't mean anything,
And then so we did the calculation. Basically, you can
taste the severe bitterness if you put one gram of
this common in a million bestubs of wow do you
You basically don't need very much of it to send

(03:04):
you puckering.

Speaker 2 (03:04):
Even if you took a bite of them one of mushrooms,
you wouldn't want to do that, okay.

Speaker 3 (03:09):
And you might go, well, who cares, Michelle, why does
this matter? It matters for a few reasons. One, this
really is the first time we found this bitter compound
in a mushroom or a fungus. We usually found these
compounds in plants or we make them chemically, and we
want to make these For example, I don't know if
you've ever had a tablet that tasted really bitter, but
they coat dangerous tablets medical tablets with a bitter tasting

(03:32):
outside so that children don't gobble them all down.

Speaker 2 (03:36):
Yep.

Speaker 3 (03:36):
And they're typically man made or chemically made. So now
you go, oh, we can just take this extra from
We literally need the tiniest bit to make a spray
chemical that we can put that's naturally made on things
like that, so de terence to stop people eating things
at a toxic Number Two, we know that our bitter
taste receptors pre date in our mouth, pre date flowering

(03:57):
plants by about three hundred million years. So the fact
this has been found in a fungus may show the
origins from an evolution perspective of why we even defer
looked bitter taste buds. It might have been because of fungus,
because it wasn't because of plants, And what I did
not know this, and I love this paper for this
bitter receptors, So there's special tas two are forty six

(04:19):
are not just on our tongue. We have them in
our lungs and in our guts, and in our heart
and in our brain in other places. But we have
them in our lungs so that if we smell something
that might be toxic, actually it sets off because it's
it sets off a whole bunch of immume responsors that
might be protecting us from something that we're inhaling. And

(04:40):
I only thought that the bitterness was tasted by a tongue,
but we actually have them everywhere else and so this,
this horrific mushroom will set them off everywhere.

Speaker 2 (04:47):
I just love us. We don't really need we're govy.
We could just have a spray spraying.

Speaker 3 (04:52):
Everything's bittered on your trugger foods. But yeah, So the
world's most bitter tasting substances come from mushroom and it's
just been found and it is really potent, fascinating.

Speaker 2 (05:02):
Thank you so much, Michelle, appreciate it.

Speaker 1 (05:05):
For more from the Sun a session with Francesca Rudkin,
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