Astragalus Root
Astragalus membranaceus

Astragalus has been used for centuries by Traditional Chinese Medicine Doctors.   It contains antioxidants, which guard cells against injury caused by free radicals.  Studies at the University of Houston have shown Astragalus is used to protect and support the immune system, for preventing colds and upper respiratory infections, to lower blood pressure, to treat diabetes, and to protect the liver.

Nutrient content of Astragalus Root, Zinc, Iron, flavonoids, choline, polysaccharides, and folic acid.

The polysaccharides found in this herb appear to be the "super stars" as they seem to have the ability to boost infection-fighting white blood cell production and spur the activity of killer T cells.

Caution / Safety
Pregnant women should not use.   Patients with bleeding disorders or on drugs that increase the risk of bleeding should also use Astragalus with caution as it can increase the risk of bleeding.
 

References - 
Encyclopedia of Common Natural Ingredients, by S. Foster
The New Age Herbalist by Richard Mabey
Jade Remedies by Peter Holmes