The work presented in this thesis is divided into two projects, the isolation and characterisation of analgesic activity in the bark of Barringtonia acutangula and the initiation of an assay for protein phosphatase activity which could be used as a high throughput screen. Analgesic activity had been reported in the bark of Barringtonia acutangula, a tree which grows across northern Australia, by aboriginal people living in the Kimberley district of NorthWwestern Australia. B. acutangula is one of four species of Barringtonia which grow in Australia and one of many which grow in tropical regions worldwide. In addition to its analgesic properties B. acutangula has been put to many uses by local peoples. These include use as medicines, construction materials and as foods. Commonly B. acutangula is used as a fish poison in the collecting of fish for human consumption.