Why the Herbs Are Decocted Together in One Pot

Herbal medicine puts several herbs in one pot and decocts them together. Combining herbs, and decocting them combined, is a subject I have studied and taught for a long time.

A patient once asked me this. "Could you not decoct them separately and mix them afterwards?"

It is a good question. The compounds all go in either way, so it seems. Today I want to look at this old method through the eyes of chemistry.

Chemistry happens inside the one pot

Let me start with the fact. What is decocted together and what is decocted separately then mixed do not have the same composition. This is not a matter of taste; it is a measured difference.

There is a study that took Coptis and Scutellaria as its example. Comparing the two herbs decocted separately and mixed against the two decocted together from the start, the distribution of the compounds had been rearranged. Some compounds went up, some went down.

Why this happens has been worked out as well. The compounds stick to one another. An alkaloid from one side and a glycoside from the other pair up through hydrogen bonding and gather. In other words, a reaction is going on inside the pot.

There is a study that went further. Simply mixing the two herbs produces nano-scale fibre-shaped structures, but decocting them together produced ball-shaped structures. And the co-decocted side was the stronger of the two at holding back bacteria in the laboratory.

What is decocted separately and mixed is not the same water as what is decocted together.

Some herbs dissolve out the others

There is another strand to this. It is the case where the compounds of one herb make other compounds dissolve better in water.

Licorice has been studied as an example of this. Licorice's saponins are friendly to both water and oil, so they wrap compounds that dissolve poorly in water and pull them in. There are measurements showing the extracted amount of certain compounds rising several-fold when decocted together.

On top of this, there is research showing that licorice's compounds block the pump that pushes a drug back out of the gut. As a result, in a co-decocted prescription the blood concentration of another herb rose markedly. This was confirmed in animals.

The ancients put licorice into a great many prescriptions. I did not learn the reason for that from chemistry — I learned it from Korean medicine first, and later had the experience of chemistry attaching a reason to that same place. Of course I cannot state flatly that this was exactly the reason for the old usage. But each time I see the direction line up, I feel the pleasure of studying this medicine.

Combining is not addition

So this is the frame I use when I look at how a prescription is combined.

Adding one more herb is not adding one more compound. It is redrawing the whole terrain. Some compounds go up, some go down, some appear that were not there. Which is why herbs are not put in and taken out carelessly.

This connects to the many-layered action I always talk about. Not one compound pressing one spot, but several compounds moving a little at several sites and so changing the body's environment. (Herbal medicine doesn't press one spot)

In people

The chemistry is solid, but when you go to human data it is still thin.

To give one striking piece: there is a study that used a prescription made of four herbs alongside cancer treatment. The gut side effects caused by the anticancer drug were reduced, and the way it happened is interesting. This prescription did not prevent the initial damage itself that the anticancer drug causes. Instead it helped the damaged gut's stem cells grow back.

This part connects to what I always say. The medicine did not act in the body's place; it pushed the environment toward the body repairing itself.

That said, this is a study done with a set anticancer drug, a set prescription, and set conditions. If you are receiving cancer treatment, please do not take herbal medicine on your own judgement — tell both the place treating you and the Korean medicine clinic. I do not prescribe without that information.

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We started from the question of whether the herbs could be decocted separately and mixed.

The answer is this. What comes out is not the same. Inside the one pot the compounds stick to each other, dissolve each other, and settle out. The water that results is not the same water as each of them added together.

Inside that old choice — putting them in one pot — things are happening that chemistry has only now begun to measure. What is happening is fairly visible; what it means for people starts from here. Filling in the space between the two is, I think, my generation's share of the work.

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References

• The difference in compound composition between decocting together and decocting separately — Pharmaceuticals, 2025
• Decocting together changes the nano-structure and raises antibacterial strength — Journal of Nanobiotechnology, 2022
• Why the blood concentration of another herb rose in a co-decocted prescription — Frontiers in Pharmacology, 2018

Written by Dr. Heo Ji-young (PhD in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)