Step 1: Understanding the Concept:
Punarnava is an Ayurvedic drug used for edema (fluid retention) and kidney diseases. "Punarnava" means "that which makes one new again."
Step 2: Detailed Explanation:
1. Components: The plant contains an alkaloid (punarnavine) and several flavonoids (like boeravinones). Crucially, it is also very rich in potassium salts (especially potassium nitrate).
2. Diuretic Action: High concentrations of potassium salts promote diuresis (increased urination) by creating an osmotic effect in the kidneys. Flavonoids also contribute significantly to the overall renal protective and diuretic effect.
Step 3: Final Answer:
While it contains alkaloids, its traditional use as a diuretic is clinically attributed to its high potassium and flavonoid content.