Most bitter tasting substance on Earth identified by scientists

Most of us experience bitterness as a simple taste – something triggered by a vegetable that makes us wrinkle our noses and push a plate away.

But there’s more going on behind the scenes. The molecules that cause bitterness can vary wildly in shape and source, and scientists are still piecing together how our bodies recognize and react to them.

The mystery of a bitter mushroom

A recent study has taken that search into lesser-known territory, using a forest mushroom with an extremely bitter flavor to find out more.

In a collaborative effort, scientists from the Leibniz Institute for Food Systems Biology at the Technical University of Munich and the Leibniz Institute of Plant Biochemistry in Halle (Saale) set out to explore the bitter properties of Amaropostia stiptica, commonly called the bitter bracket mushroom.

This fungus can be found growing on the trunks and branches of dead trees. It has a shelf-like fruiting body that juts out from the wood and, although not harmful, it is known for its intensely bitter taste.

Understanding Amaropostia stiptica

Amaropostia stiptica is a crust fungus that hangs out mostly on decaying wood, especially in tropical and subtropical forests.

You’ll spot it forming thin, resiny patches on dead hardwood, often with a waxy or slightly sticky texture. Its surface tends to look smooth to slightly bumpy, and it usually has a pale color – think creamy beige to light yellow.

Even though it’s not flashy, it plays a crucial role in breaking down tough plant material, recycling nutrients back into the forest floor.

While it’s not edible or medicinal, this fungus still earns respect for doing the gritty work of decomposition in ecosystems where that kind of job is essential.

What we know about bitter compounds

Most of what we know about bitter compounds comes from flowering plants or synthetic chemicals.

In fact, the BitterDB database – the main catalog of known bitter molecules – currently lists over 2,400 entries. For around 800 of them, researchers have matched at least one specific human bitter taste receptor.

But animal, bacterial, and fungal sources of bitter compounds are still a mystery. This makes mushrooms an ideal place to look for new insights.

Not all bitter compounds are toxic

Our bodies rely on bitter receptors, called TAS2Rs, to warn us against potentially dangerous substances. But there’s a twist: not all bitter compounds are toxic, and not all toxins taste bitter.

The infamous death cap mushroom, for example, contains toxins that don’t taste bitter at all. Clearly, something more complex is happening.

Adding to the mystery, bitter taste receptors aren’t only found on the tongue. They also show up in the stomach, intestines, heart, lungs, and even on some blood cells.

These receptors aren’t used for tasting in the traditional sense, so scientists wonder what role they’re playing in the rest of the body.

Identifying new bitter compounds

“Comprehensive data collections on bitter compounds and their receptors could help us to find answers to these open questions,” said Maik Behrens, who heads a research group at the Leibniz Institute in Freising.

“The more well-founded data we have on the various bitter compound classes, taste receptor types and variants, the better we can develop predictive models using systems biology methods to identify new bitter compounds and predict bitter taste receptor-mediated effects.”

This applies to both food constituents and endogenous substances that activate extraoral bitter taste receptors.

To support this effort, the team focused on finding new, underrepresented sources of bitterness. Their latest work adds rare fungal-derived compounds to the growing database of known bitter substances.

Mushroom with three bitter compounds

Using advanced analytical techniques, the team identified three new bitter compounds from Amaropostia stiptica and mapped out their chemical structures.

When tested in cell-based systems, all three compounds triggered at least one of the human bitter taste receptors.

The standout discovery, however, was a molecule called oligoporin D. This substance activates the TAS2R46 receptor at extremely low concentrations – about 63 micrograms per liter.

To put it in perspective, that’s like dissolving a single gram of the compound into more than 100 bathtubs of water. One gram is about the same as the tip of a knife full of baking soda.

Bitterness as a clue to better health

“Our results contribute to expanding our knowledge of the molecular diversity and mode of action of natural bitter compounds,” explained Behrens.

“In the long term, insights in this area could enable new applications in food and health research, for example in the development of sensorially appealing foods that positively influence digestion and satiety.”

The discovery of new bitter molecules from fungi shows just how much is left to learn. Bitterness isn’t just a taste – it’s a signal, a potential tool, and possibly even a pathway to better health.

With each new entry into the bitter compound database, researchers come one step closer to understanding how taste shapes our bodies in ways we’re only just beginning to grasp.

The full study was published in the Journal of Agricultural and Food Chemistry.

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