Plants that can offer cures for many serious diseases could be lost because of deforestation in Borneo, according to the World Wildlife Fund (WWF).
Much of the deforestation has been blamed on illegal logging
Such plants could be used in the fight against cancer, Aids and malaria, the conservation group said in a report.
But the WWF warned that such knowledge could be lost "if the disappearing rainforests of the heart of Borneo are not adequately protected".
Much of the deforestation on the island has been blamed on illegal logging.
Only half of Borneo's forest cover remains intact, down from 75% in the mid-1980s, the report said.
A total of 422 new species have been discovered in Borneo in the last 25 years, the campaign group said. But it added that many others had yet to be found.
As an example of the medical advances already made, the WWF cites the discovery of a potential anti-cancer compound found in the shrub Aglaia Leptantha, by the Australian pharmaceutical company Cerylid Biosciences.
The substance has been found to kill 20 kinds of human cancer cells in laboratory tests.
"The fact that the compound is very effective against a number of tumour cells presents a very good argument for preserving the plant's habitat in Borneo," Murray Tait, vice president of drug discovery at Cerylid Biosciences, is quoted as saying.
"More forest destruction could well deny science the opportunity to discover and develop further potential sources of life-saving medication."
The three nations which claim territory in Borneo - Brunei, Indonesia and Malaysia - have recently launched a joint initiative to preserve some of their equatorial forests.
The WWF hopes these three governments will soon sign a pact to help secure the area.
"Such a declaration would ensure long-term protection to a region which might contain some of tomorrow's most significant medical discoveries," said Mike Kavanagh, Chief Executive Director of WWF-Malaysia.