However, so far no more than 10 percent of all the plant and animal species in the world's rain forests have been studied for their possible medical benefits.
(no more than 10 percent of all the plant and animal species in the world's rain forests; have been studied; T:for their possible medical benefits; T:so far)
no more than 10 percent of all the plant and animal species in the world's rain forests
have been studied
T:for their possible medical benefits T:so far