From my dish of pasta?
Martin-Luther-Universität Halle-Wittenberg
Their essential oils contain thymol and carvacrol which impart the typical flavors and are medically important. A team from Martin Luther University Halle-Wittenberg (MLU) and Purdue University in the USA has now fully identified how the plants produce these two substances.
The results could
simplify the breeding process and improve the pharmaceutical value of thyme and
oregano. The study appears in the journal Proceedings of the National
Academy of Sciences.
Thymol, which is mainly extracted from thyme, has secretolytic, antibacterial and antispasmodic properties.
The plant is therefore often used in tea for colds, cough syrups and as an herbal remedy for bronchitis. In contrast, oregano contains particularly high levels of carvacrol, which has similar properties. Its smell is often associated with pizza sauce and other Mediterranean dishes. Both substances are chemically closely related and are produced by thyme and oregano in multi-stage processes.
"It's like a production line in a factory: Every step needs to be coordinated and the desired product only emerges when the steps are carried out in the right order," explains Professor Jörg Degenhardt from the Institute of Pharmacy at MLU.
Instead of
machines, specific biomolecules -- enzymes -- carry out this work in special
glands on the surface of the leaves.
Together with researchers from Purdue University in the USA, the team in Halle decoded the individual production steps, thereby solving a decades-old mystery. "For a long time it was assumed that p-Cymene was an intermediate product of thymol and carvacrol synthesis. However, it was chemically not feasible for thymol or carvacrol to ultimately be produced from this substance," says Degenhardt.
In fact, normal production of the two substances does not produce any p-Cymene at all, but rather an extremely unstable intermediate product. "This is only present for a few moments in the plant cells, which is why observing it is so difficult. However, it represents the hitherto missing step in the synthesis of the two substances," says Degenhardt.
The processes start out the same for both
thymol and carvacrol; only in step four do different enzymes that produce the
respective substances come into play. In a fifth step, thymol and carvacrol can
be further converted to thymohydroquinone and thymoquinone, which have
anti-inflammatory and anti-tumour effects.
The
researchers were also able to use these new findings to genetically reprogramme
a species of tobacco, the model plant N. benthamiana, to produce
thymol. "Even though this only happened in small quantities, it meant that
we were able to fully understand the synthesis pathways and the associated
enzymes," summarises Degenhardt.
The new findings are also important for plant breeding. "Up to now, plants have mostly been crossbred randomly with one another and then selected for cultivation based on their smell," says Degenhardt.
This new molecular
knowledge may one day enable the development of biomarkers for the targeted selection
of plants with high essential oil content. The findings could also help to
develop new active substances based on thymol, carvacrol and thymohydroquinone
to fight bacterial infections, inflammation and cancer.