From DW:

Youyou Tu, the chief professor at the China Academy of Traditional Chinese Medicine, began her work with traditional herbal remedies in the 1960s.

Focussing on plant Artemisia annua, Tu extracted the active Artemisin ingredient found in plants, then purified it. Tests conducted by the now 84-year-old showed her trials had “unprecedented potency” in treating Malaria, which infects close to 200 million people every year. The infection leaves more than 450,000 people dead globally annually, with most of the victims being children.

The other 2015 Nobel prize was for another antimicrobial therapy with an "A", Avermectin.

Nobel Medicine Prize 2015 - Announcement And Explanation:



Read more here:
http://buff.ly/1VALadf
Nobel Prize for anti-parasite drug discoveries - BBC News http://buff.ly/1M6DTkL

Full video is below (42 minutes):