I have used these leaves and currently using leaves from birch tree.
No need to boil the leaves or rinse them for that matter so long as you are certain no pesticides or other chemical's have been used on tree's or ground where leaves are lying.
I gather enough leaves in the fall after they are dry and only soak em for a day or two until thety sink in the bucket otherwise,,they will float for a day or two in the aquarium
Tannin's they relase cause no harm to fishes, but do stain the water depending on how many and what size the leaves are.
Personally think there are infusoria cyst's on the leaves that young fishes and shrimp readily get after, so is another reason not to boil them.(have seen shrimp's young fish feed from the leaves)
I normally let the leaves deteriorate and replace em once the original's are all but gone.