From the Manufacturer:
Elderberry extract comes from the fruit of the Sambucus nigra or Black Elder, a species found in Europe, Western Asia, North Africa, and North America. Called “the medicine chest of the common people,” Elder flowers, berries, leaves, bark, and roots have all been used for centuries in traditional folk medicines. Elder fruit contains vitamins A, B and C, flavonoids, tannins, carotenoids, and amino acids. Elderberry is believed to possess therapeutic uses as an anti-flammatory, diuretic, and immuno-stimulant.
The best documented aspect of elderberry is its anti-viral effects. Elderberry has long been used to support a healthy immune system.