Can you get oxygen by smelling leaves?
Not any important amount more than what you're already getting from the surrounding air.
A tree absorbs carbon dioxide through its leaves, extracts the carbon to contribute to its growth, and releases the oxygen through its leaves. A tree also absorbs water through its roots, extracts the hydrogen to contribute to growth, and releases the oxygen through its leaves. That is how trees produce oxygen.
Why does makahiya leaves guava leaves and madre de cacao leaves effective in making mosquito repellent?
Carry water to the leaves and carry sugar and oxygen from the leaves to the living parts of the plant that need it?
Almost all of the mints I have in my garden ( 6 in all) have pleasant smelling leaves ( cat mint is a bit musky) and of those 4 have some shade of purple flowers, the other two are white and a pinky purple. I recommend a good gardening book, they often have pictures to help you identify your plant. The size, shape and colour of the leaves are more often what will be the…