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Malaria has been haunting humans  for as long as we’ve existed. And for a long time, there was no widely-known  cure that worked on all strains of it.

But in the 1970s, the scientist Tu Youyou  identified an ancient Chinese remedy that eventually became one of the main  modern defenses against this disease. And thanks to her, it’s now saved  countless lives over the last 50 years. Tu was born in the Chinese city of Ningbo in 1930, and originally didn’t plan to  dedicate her life to medicine.

But at 16, she got sick with tuberculosis  and had to leave school for two years. And after she recovered, she became determined to find cures for illnesses  like the one she’d experienced. So, she studied pharmaceutics  at Beijing Medical College and later went on to study at the  Academy of Traditional Chinese Medicine.

Then, Tu started her career as a  researcher. She studied herbs used in traditional Chinese medicine as a  way of treating parasitic infections. And that soon made her the perfect  person for a very important job.

In 1967, during the Vietnam War,. North Vietnam reached out  to China for medical help. At the time, malaria was  spreading among its troops, and they were dying in large numbers.

To make matters worse, the  parasite that causes malaria had become resistant to the main treatment  they were using, called chloroquine. So China put together an  initiative called Project 523 to find a cure for this deadly strain of malaria. And in 1969, Tu became the head of it.

She and her research team started  out by traveling to Hainan Island in southern China, where  there was a malaria outbreak. There, they could see the  effects of the illness firsthand and research effective treatments in the field. Then, once they had a better understanding  of the disease, Tu and her team returned to Beijing and started looking for  remedies in ancient Chinese medical texts.

Since malaria has been around for so long,  it was a frequent topic in these writings. And the team had over two  millennia’s worth of work to study… so they got down to business. They tested 240 thousand compounds on  mice that had been infected with malaria.

And… nothing worked. But then, while looking back over her  notes, Tu found an interesting reference to the herb qinghao, also known as sweet wormwood. She had tested qinghao before and  found that it had some effect, but it wasn’t reliable enough to make  this herb a serious choice for treatment.

The reference made her dig  a little deeper, though. And while reading a text from around 400  C. E., Tu realized that the authors weren’t boiling the leaves to collect  the extract, as she’d done.

Instead, they were immersing the leaves  in water and wringing out the juice. Basically, they were making an extract  of qinghao without heating it at all. So Tu tried following those instructions:.

She made what’s called an ether solution, where the leaves are steeped in  a mixture of water and alcohol. This extracted the active compounds in the herbs — without breaking them down, as boiling can do. And this time, when she tested  the compound on mice and monkeys, it cured malaria 100% of the time.

They still hadn’t tried it out on  humans, though, so as a final step,. Tu and her colleagues tested the  medicine for side-effects on themselves. Then, they delivered it to  21 patients on Hainan Island.

And, incredibly, every  single one of them recovered. As it turned out, the key to this life-saving cure was an active compound from the  wormwood plant called artemisinin. And it’s effective against malaria  because of the way it interacts with the parasites that cause the disease.

Once they mature, these parasites  contain a compound called hemozoin — something they ultimately get  from digesting human blood. And when artemisinin encounters hemozoin, the two compounds react to create  unstable atoms known as free radicals. Those atoms have uneven numbers of electrons, unlike most atoms and molecules,  which have electrons in pairs.

As a result, free radicals react  extremely readily with other atoms — to the point where they can  actually tear cells apart. And these violent reactions destroy the parasites. Which is kind of satisfying: feeding on human blood is ultimately  the thing that kills them.

Now, artemisinin can be toxic to  human cells, too, for the same reason. It can react with compounds in our  bodies and create those free radicals. But luckily, artemisinin reacts  more readily with hemozoin, than it does with the iron in our cells.

It takes a pretty high dose to damage human cells, so by controlling the dose, it’s possible  to make sure only the parasite dies. Today, artemisinin is still distilled  from the dried leaves or flower clusters of the sweet wormwood plant  and used to treat malaria. In fact, two decades after Tu’s  discovery, the World Health Organization recommended that artemisinin be  used in combination with other drugs as the first line of defense against malaria.

And in 2015, Tu received the Nobel  Prize in Physiology or Medicine, along with the American  parasitologist William Campbell and Japanese microbiologist Satoshi Ōmura. But in spite of all the honors  she’s received, Tu has said that her biggest accomplishment is doing  something to help the world — and there is no doubt that millions of people have survived  or lived healthier lives thanks to her. If you enjoyed this, you might like  some of our other Great Minds videos, which like the name says, celebrate  some of the greatest minds in science.

If you want a place to start, I would like  to recommend our episode about Alice Ball, a woman who changed leprosy  treatment in her twenties! [♪ OUTRO].