A study in China suggests that a commonly used Chinese herb for cold and fever contains ingredients against influenza viruses. A group of researchers of the Chinese Academy of Medical Sciences and Peking Union Medical College, as well as University of Macau investigated the anti-flu functions of the ingredients of the plant elsholtzia rugulosa, a common Chinese herb widely used in the treatment of cold and fever.

In order to elucidate the action mechanism and the active principles from the plant against anti-influenza virus, researchers established the influenza virus neuraminidase (NA) activity assay and in vitro antiviral activity assay, and the isolation of the active principles was guided by NA activity. The study established that five active constituents were found in elsholtzia rugulosa and they are all flavonoids.