Fresh Black Walnut Hulls are harvested in their green state (before they blacken) where they are more potent. Black Walnut's two main active chemicals are juglone and tannins. Juglone is antibiotic and antifungal and can have a normalizing effect on intestinal tissue. Tannins are astringents that may reduce secretions, relieve irritation and tighten tissues by shrinking the top layers of the skin. These properties allow Black Walnut Hull to assist with indigestion, diarrhea and constipation.