Many research article used same methods to prepare their plant material but some group of researchers termed that plant extracts and other some researchers are prefered to used the term plant leachates.Its really confusing for the new researchers.
These two terms may be used as synonyms. But, actually Plant extract means the chemical compounds released from the plant samples due to the extraction procedure. It can be done by using any extraction solvent including water.
But, Plant leachates are the secretory products releasing out into the environment from plants (either living or non-living) in course of time and this process is considered as a natural phenomenon.
So, these two words carry completely different senses.