Oleuropein Concentration Question

Hello,
I came across a study that claims air drying olive leafs at room temperature over a period of a few days will actually provide a higher oleuropein concentration than drying the leafs in the oven or consuming them (tea or other) fresh... are you aware of how accurate this is? and is there a simple way for one to approximately measure how much oleuropein is in each dry vs fresh leaf for example (if one is to consume olive leaf tea or powder from a garden olive tree vs. purchasing a supplement)

thank you!